Dou Lai, James Unwin
AstronomerThe authors search ten years of 1–100 GeV Fermi-LAT data for steady point sources with proper motions of 0.25–0.8 degrees per year, which stationary-source searches could miss. For an assumed transverse speed of 200 km/s, this range corresponds to distances of approximately 3,000–9,700 AU. They find 577 candidate tracks, consistent with 533 ± 27.0 tracks in time-scrambled skies, rather than establishing a moving-source population. The model-independent 90% upper limit is 80.8 recovered signal tracks. At peak calibrated sensitivity, this translates to fewer than 123 steady sources over the full sky with an incident E^-2 photon spectrum. The calibrated detection efficiency also supports illustrative constraints on evaporating primordial black holes and primordial black holes surrounded by annihilating dark matter halos; these are possible source models, not identified objects.
PublicA search for gamma-ray sources usually assumes they stay in the same place on the sky, but nearby sources could move enough to be overlooked. This study searched ten years of Fermi-LAT observations for steadily emitting sources moving by 0.25–0.8 degrees per year. It found 577 possible paths, consistent with the 533 ± 27.0 found when the observation times were scrambled, so the candidates do not establish a detection of moving sources. Instead, the researchers set limits on how many such sources could be present. Under the spectral assumption used and at the search’s best calibrated sensitivity, the limit corresponds to fewer than 123 steady sources across the sky. They also derive illustrative restrictions on possible sources involving primordial black holes and dark matter, without showing that any candidate is one of these objects.
Young explorerScientists looked for tiny spots of special light called gamma rays that might slowly move across the sky. They searched ten years of pictures and found some possible trails. But when they mixed up the times of the pictures, they found about as many trails, so they could not tell that the trails came from real moving things. Instead, they worked out limits on how many moving lights might be hiding. Some might come from things called black holes or dark matter, but the scientists did not find proof of those things here.
B. Domine, B. Liu, H. Krawczynski+3 more
AstronomerThe paper presents an AI-agent pipeline for analyzing IXPE data, combining an immutable code base with evolving knowledge databases. A literature database helps assess the novelty of proposed analyses, while separate expert guidance addresses data reduction and scientific interpretation. Multiple auditor levels scrutinize analysis plans, scripts, and results for data and method adequacy, followed by staged interpretation. Examples using IXPE observations of black hole X-ray binaries include comparisons with published results and a systematic search for polarization-degree and polarization-angle variability in long observations. The abstract reports no specific variability detections or quantitative performance measures; the paper critically discusses pipeline performance and possible improvements.
PublicIXPE measures several properties of cosmic X-rays, including polarization, which describes their preferred orientation. This paper explores how AI assistants can help analyze those measurements. The system uses fixed analysis code alongside knowledge databases that can evolve, consults published research to assess whether proposed studies are new, and includes several layers of checks on its plans, code, and results. The authors present examples involving black hole X-ray binaries, compare their analyses with published work, and search long observations for changes in polarization. The abstract does not say whether those changes were found or how accurately the system performed, and the authors discuss limitations and future improvements.
Young explorerA space telescope called IXPE studies a kind of light called X-rays from things in space. The researchers use computer helpers to study its measurements, with instructions and checks to help catch mistakes. They show examples using light from systems with black holes, compare their work with earlier studies, and look for changes in how the light is lined up. This short description does not tell us whether they found those changes, and they discuss how to make the helpers better.
Silvia A. Popa, Selma E. de Mink, Stephen Justham+3 more
AstronomerThis modeling study extends the proposed chemically homogeneous evolution (CHE) channel from isolated binaries to hierarchical triples, coupling detailed MESA models of the inner CHE binary to analytical triple-dynamics prescriptions. Von Zeipel–Lidov–Kozai eccentricity excitation allows the tertiary to accelerate inner binary black-hole mergers and enables mergers at higher metallicities where classical binary CHE does not operate. At one-third solar metallicity, the modeled triples yield black-hole masses around 15 solar masses and dimensionless spins around 0.25, rather than the masses above roughly 35 solar masses and large, orbitally aligned spins predicted for isolated CHE binaries. Spin-orbit misalignment and possible residual eccentricity at merger are further expectations, not reported observational findings. At this metallicity, half of the modeled mergers occur within 1 Gyr; 10% of the population produces prompt mergers within 1 Myr and 1% within 1 kyr, potentially relevant to electromagnetic counterparts. The authors suggest that shorter delays and access to higher metallicities could increase CHE’s contribution to the local merger rate. The predicted lower masses and spins more closely resemble those inferred for most observed gravitational-wave mergers, but the study does not establish their formation channel.
PublicHow pairs of black holes form before merging remains debated. One proposed route involves two stars evolving with thoroughly mixed chemical contents, but studies of this route in isolated pairs predict heavier, faster-spinning black holes than those inferred for most observed gravitational-wave mergers. This study models what happens when a third star is present. Its gravitational influence can stretch the inner pair’s orbit and hasten their eventual merger. At one-third the Sun’s abundance of elements heavier than helium, the models produce black holes weighing about 15 Suns, with lower spins than in the classical two-star scenario. Half of these modeled mergers occur within a billion years, and some occur much sooner. The researchers also expect tilted spins and possibly noncircular orbits at merger. These predictions suggest that three-star systems could make this formation route more important, but they do not prove that it explains the observed mergers or that the fastest mergers produce accompanying light.
Young explorerScientists are trying to understand how two black holes get together and merge. They used computer models to explore what happens when two stars have a third star nearby. The third star can tug on the pair and help the black holes they become merge sooner. In these models, the black holes can also be lighter and spin more slowly. This is a possible explanation, not something the scientists have proved happens in the mergers we see.
Gaurava K. Jaisawal, Georgios Vasilopoulos, Francesco Carotenuto+1 more
AstronomerA multiwavelength study follows the poorly studied Be/X-ray binary GS 1843+00 through its February–May 2026 outburst after nearly sixteen years of quiescence. Three NuSTAR observations reveal coherent pulsations near 29.7 s and a spin-period derivative of (−5.1 ± 0.1) × 10⁻⁸ s s⁻¹. Pulse morphology evolves with energy and outburst phase, differing even at comparable luminosities. Pulsed fractions span 1–16%; above 7 keV they increase with energy in the first two observations but decrease in the third. The 3–79 keV spectra are described by thermal Comptonization, a blackbody, and Fe Kα emission, with no evidence for cyclotron absorption. Phase-dependent spectral parameters are interpreted as indicating changes in accretion-column structure. Optical Hα and Paschen emission confirm a Be-circumstellar disk; weaker Hα than at previous epochs indicates a different disk state during this episode. MeerKAT detects no radio counterpart, placing a 3σ upper limit of 36 μJy beam⁻¹ at 1.28 GHz. This non-detection suggests any associated outflow was faint or below the detection limit, rather than establishing its absence.
PublicAfter nearly sixteen quiet years, the binary star system GS 1843+00 underwent a major X-ray outburst between February and May 2026. Observations show that its neutron star produced X-ray pulses roughly every 29.7 seconds and spun faster during the outburst. The pulses changed shape with X-ray energy and as the outburst progressed, even when the system had similar brightness. Changes in the X-ray spectrum suggest that the structure of gas falling onto the neutron star also changed. Optical observations confirmed a disk of gas around the companion Be star. One emission line was weaker than in earlier observations, indicating that this disk was in a different state. No radio source was detected at the system’s position; any associated outflow may have been too faint to detect.
Young explorerTwo stars live together, and one is a tiny neutron star that spins. After a long quiet time, the pair became bright in X-rays. The neutron star’s X-ray flashes changed, and it spun faster. Scientists also saw signs of a gas disk around the other star. They found no radio signal, but a faint one could have been missed.
Qiu-Hong Chen, Meng-Hua Chen, Xianlin Yang+1 more
AstronomerThis computational study examines delayed decay-chain feeding in actinide cosmochronology, an age-dating method independent of Galactic chemical evolution models but limited by uncertainties in initial abundances and subsequent evolution. The authors couple a self-consistent radioactive decay network incorporating all relevant decay pathways to r-process nucleosynthesis calculations using neutron star merger trajectories. They identify thorium-232, uranium-235, uranium-236, uranium-238, and plutonium-244 as the dominant long-lived nuclei governing the modeled evolution of Th and U. Delayed feeding particularly affects thorium-232 through late contributions from heavier progenitors, including plutonium-244 and uranium-236. In these calculations, U/Th and Th/X chronometers are sensitive to this feeding, with estimated age corrections reaching approximately 5 Gyr. These are model-based corrections, not measured revisions to particular objects’ ages, and the results indicate that long-lived progenitor feeding should be included in actinide age determinations.
PublicRadioactive thorium and uranium can serve as clocks for estimating the ages of astronomical objects, but using them requires knowing how much was originally produced and how their amounts changed over time. This study uses calculations of element production in neutron star mergers, together with a network of radioactive decays, to investigate those changes. The models show that heavier radioactive nuclei can slowly decay into the clock elements, adding material long after it was first made. Thorium-232 is especially affected by contributions from plutonium-244 and uranium-236. Accounting for this delayed supply changes some calculated age estimates by as much as about five billion years. The study does not report measured age revisions for specific objects; it highlights an effect that models of these radioactive clocks need to include.
Young explorerScientists can use tiny bits of radioactive stuff like clocks to help work out how old things in space are. But other stuff can slowly turn into the clock’s material, changing what the clock seems to say. In computer calculations, scientists found that this could change an age answer by as much as about five billion years. They need to count that extra material to read the clock properly.
Sheng-Lun Xie, Yi Zhao, Wen-Long Zhang+3 more
AstronomerThe authors argue that magnetar X-ray flares (MXFs), short substructures within conventionally defined bursts, are the elementary units of magnetic energy dissipation. In 789 MXFs from SGR J1935+2154, waiting times separate into two components, interpreted as clustered intra-episode events and longer inter-episode intervals. The proxy emission measure and temperature show distinct rising and declining trends, while the energy release scale proxy distribution has a high-end slope in the same statistical regime as solar and stellar flares. Combining these findings with a previously measured duration slope, the authors interpret MXFs as a three-dimensional fractal-diffusive self-organized critical system with a diffusion parameter of approximately 2. This model implies reconnection avalanches expanding linearly through an active magnetosphere. They infer that active episodes are global unloading states composed of many elementary flares; the physical mechanism and episode picture are interpretations of the statistical evidence, rather than direct observations.
PublicThe study suggests that the key building blocks of magnetar activity are not whole bursts, but the shorter X-ray flashes inside them. Analyzing 789 such flashes from SGR J1935+2154, the researchers found two groups of waiting times, which they interpret as gaps between flashes within an episode and longer gaps between episodes. They also found distinct rising and declining patterns in temperature and an indirect measure of the emitting material. An indirect measure of energy release has a distribution whose high-energy end falls in the same statistical range as flares on the Sun and other stars. Together with an earlier result about flash durations, these patterns support the authors' interpretation that magnetic energy is released in spreading avalanches, with larger active episodes built from many smaller flares. The avalanche mechanism is inferred from the patterns, not directly observed.
Young explorerA magnetar can make bursts of X-ray light. Scientists looked at 789 little flashes inside those bursts. Some flashes came close together, and others had longer waits between them. The scientists think these little flashes may be the important pieces of a bigger burst, like many small pieces making one big picture. They think magnetic energy spreads and makes more flashes, a bit like an avalanche. That is their explanation for the patterns they found, not something they watched happen directly.
Shi-Ju Kang, Yue Yin, Yong-Gang Zheng+2 more
AstronomerAnalysis of approximately 17 years of Fermi-LAT observations of the blazar 4FGL J0136.5+3906 reveals a bump-like spectral excess peaking at approximately 19 GeV in the observer frame within the 100 MeV–1 TeV spectrum. The reported significance is approximately 5.7σ for 3 degrees of freedom, without correction for trials or the look-elsewhere effect; the excess flux is approximately 3.6 × 10^-10 photons cm^-2 s^-1. No similar feature is detected in nearby sources or background regions. The authors report that standard blazar emission models cannot explain the signal and offer no definitive physical interpretation.
PublicResearchers analyzing about 17 years of Fermi-LAT observations report an unexpected bump in the gamma-ray spectrum of the blazar 4FGL J0136.5+3906, peaking at about 19 billion electron volts as observed. The reported statistical significance is about 5.7 sigma, but it has not been adjusted for the possibility of finding a feature by chance when searching multiple possibilities. No similar bump was detected in nearby sources or background regions. Standard models of blazar emission do not explain the feature, and its origin remains unknown.
Young explorerScientists studied about 17 years of observations of a space object called a blazar. They found extra gamma rays, a kind of light, around one energy—a bump in their graph. They did not find a similar bump in nearby objects or background areas. The bump looks like a strong clue, but their calculation has not yet accounted for all the chances of finding a bump by accident. The usual explanations do not explain it, and the scientists do not yet know what caused it.
Kaushik Chatterjee, Min Wei, Jie Liao+13 more
AstronomerNear-simultaneous Insight-HXMT and XRISM observations tracked the spectral and timing evolution of the dynamically confirmed Galactic black hole transient GS 1354-64 during its 2025–26 outburst. The early hard-intermediate spectrum featured a hot Comptonizing corona and relativistically broadened reflection. As the source softened, the corona cooled, the photon index steepened to approximately 2.5 or greater, and reflection features, including broad Fe K-alpha emission, were suppressed, leaving a featureless, disk-dominated continuum. Type-C QPO frequencies rose from 0.25 to 6.52 Hz, while low-frequency hard lags declined from approximately 160 ms to near zero. Crucially, accounting for measurement uncertainties yielded no significant monotonic correlation between broadband lags and QPO frequency, photon index, or fractional rms. The authors interpret the spectral softening and QPO acceleration as strong evidence for coronal contraction within either Lense-Thirring precession or TCAF interpretations. They suggest competing positive Comptonization and negative thermal-reverberation delays explain the scattered lag behavior, with the timing properties indicating a turbulent, inhomogeneous inner flow rather than a simple lag–geometry relationship.
PublicAstronomers used Insight-HXMT and XRISM to follow an outburst of the black hole system GS 1354-64. Its X-rays changed from a spectrum dominated by a very hot cloud of gas, called a corona, to one dominated by the surrounding disk. Broad reflection features faded, and a repeating pattern in the X-ray brightness became faster. Together, these changes strongly suggest that the corona cooled and shrank, although its shrinking is an interpretation of the observations rather than a direct image. Delays between harder and softer X-rays also became much smaller. However, once measurement uncertainties were included, those delays showed no statistically significant steady relationship with the oscillation frequency or other measured properties. The researchers suggest that competing light-delay processes in an uneven, turbulent flow could explain this more complicated behavior.
Young explorerScientists watched X-rays from hot gas around a black hole. As the gas cooled, the light changed, and a repeating wiggle in its brightness got faster. These clues suggest that a hot cloud around the black hole became smaller. But some changes in when the light arrived were messy, so the scientists think more than one thing may be happening.
Ren-Jie Xiong, Zi-Qi Wang, Xiao-Li Huang+1 more
AstronomerA multiwavelength reanalysis of GRB 240825A identifies an early, spectrally soft prompt plateau followed by a bright, spectrally hard gamma-ray pulse. The authors interpret this sequence as consistent with proto-magnetar dipole spin-down followed by collapse and a fallback-fed black-hole jet powered through the Blandford-Znajek mechanism. With simulation-motivated initial black-hole masses and spins, fits to the second episode imply disk-supply masses of 0.45–0.96 solar masses, fallback radii of 16.9–17.6 gravitational radii, and fallback timescales of 0.13–0.25 s. Maximum inner accretion rates span 0.18–0.70 solar masses per second and are sensitive to the assumed initial spin. Joint optical–X-ray spectral fits infer coupled evolution of dust extinction and equivalent hydrogen column density. Accounting for evolving extinction, a forward–reverse shock model in a wind-like medium can reproduce the radio-to-GeV afterglow. Late optical reddening is compatible with, but does not establish, a supernova contribution; dust and host-galaxy brightness could obscure it. An empirical prompt-peak-energy–supernova-luminosity relation gives an illustrative peak bolometric magnitude of −19.46 ± 0.35 for a putative supernova. The findings support, rather than uniquely demonstrate, the proposed two-stage engine and evolving dusty environment.
PublicReexamining observations of gamma-ray burst GRB 240825A, researchers found two distinct opening episodes: a relatively steady phase dominated by lower-energy radiation, followed by a bright pulse of higher-energy gamma rays. They propose that a short-lived, strongly magnetized spinning star powered the first phase, then collapsed into a black hole whose infalling material powered a fast jet. Model fits are consistent with this explanation, but do not prove it. Fits to the later glow also indicate changing absorption by dust and gas. Allowing for that change, a model of shocks moving through a wind-like environment can explain observations from radio waves to very high-energy gamma rays. Late optical reddening could include light from a supernova, but no supernova is established: dust and the bright host galaxy could hide it. The paper’s estimated supernova brightness is illustrative, not a measurement.
Young explorerScientists looked again at a big flash in space. First came gentler light, then a much brighter burst of stronger light. They think a spinning star may have powered the first part, then become a black hole that helped make the second part. That story fits the light, but it is not certain. Dust may have hidden another exploding star, so scientists cannot say they saw one.
Payaswinee Arvikar, Prashant Thakur, Sarmistha Banik
AstronomerThis unified Bayesian analysis compares Higgs-portal, neutron-decay, and axion-like-particle (ALP) dark-matter scenarios in neutron stars under a single-fluid approximation and a common relativistic mean-field hadronic description. Constraints combine finite-nucleus and heavy-ion data, chiral effective field theory, NICER measurements of four pulsars, and GW170817. Dark-sector parameters remain weakly constrained, while model-dependent shifts in nuclear skewness show that the inferred hadronic equation of state depends on the assumed dark-matter mechanism. Mass-radius and tidal-deformability predictions substantially overlap, with median maximum masses near 2.1 solar masses. At 1.4 solar masses, the Higgs-portal scenario predicts higher f-mode frequencies and shorter damping times than neutron decay and ALP, but credible regions overlap. Including three consistently reanalysed two-fluid models, neutron decay has the largest Bayesian evidence: under the adopted priors, Bayes factors are approximately 24–37 against Higgs-portal and the two-fluid alternatives, but only 2.2 against ALP. This ranks complete models, not fluid descriptions, and does not establish evidence for dark matter. Improved nuclear constraints and future gravitational-wave asteroseismology could help separate hadronic and dark-sector contributions.
PublicThe researchers used nuclear-physics information, pulsar measurements, and gravitational-wave data to compare three models of how dark matter might affect neutron stars. These are possible explanations, not detections of dark matter inside the stars. The models predict very similar stellar masses, sizes, and responses to tidal forces, and the properties of the proposed dark matter remain poorly pinned down. Their median predicted maximum masses are close to 2.1 times the Sun’s mass. For stars of 1.4 solar masses, one model predicts faster vibrations that fade sooner, but the uncertainty ranges overlap those of the other models. A broader statistical comparison favors the neutron-decay model under the researchers’ chosen assumptions, although its advantage over the axion-like-particle model is modest. This does not show that dark matter is present or that describing the star as one fluid is generally better than using two. Better nuclear constraints and future gravitational-wave studies of stellar vibrations could help distinguish the possibilities.
Young explorerNeutron stars are very tightly packed stars. Scientists used measurements and physics to compare three ideas about how mysterious dark matter might change them. The ideas predict stars that look much alike, though their vibrations might differ. One idea fits best in their comparison, but that depends on the choices they made, and another idea is close behind. They have not shown that dark matter is inside these stars. Better information might help tell the ideas apart.
Anna V. Bilous
AstronomerMotivated by tentative evidence from surface thermal X-ray pulse modeling for non-dipolar fields in millisecond pulsars, this numerical study extends the classical rotating vector model (RVM) to static vacuum magnetospheres containing centered dipole and quadrupole components. The authors calculate open field line regions (OFLRs), emission skymaps, and polarization position-angle (PA) curves across field configurations and viewing geometries, using trial spin periods of 1 and 5 ms. In these models, quadrupole contributions substantially change OFLR morphology and area; the area varies non-monotonically with quadrupole strength and sometimes exceeds the pure-dipole value. PA behavior falls into three broad regimes: nearly dipolar, largely altitude-insensitive swings; moderately distorted, altitude-dependent tracks that can bias dipolar RVM fits; and strongly dispersed behavior from different OFLRs that can resist a single dipolar fit even over narrow altitude ranges. The modeling shows that dipole-like PA curves do not uniquely establish a purely dipolar field. However, global quadrupole components alone do not reproduce the full complexity of observed millisecond-pulsar PA profiles.
PublicAstronomers often interpret the polarization of pulsar radio waves using a magnetic field shaped like that of a simple bar magnet. Tentative clues from modeling X-ray pulses suggest that some rapidly spinning pulsars may have more complicated fields. This study tests that possibility with computer models that add a quadrupole magnetic component to a dipole, rather than directly measuring pulsar fields. The added component changes both the regions of open magnetic field lines and the predicted polarization patterns. Depending on the field and viewing direction, the polarization can look almost unchanged, become moderately distorted, or become too complicated for a single simple-field model to describe. The open-field area does not simply increase as the added component grows. The key caution is that simple-looking polarization does not prove a simple magnetic field, while this added magnetic component alone cannot explain all the complexity seen in real millisecond pulsars.
Young explorerPulsars are spinning stars whose radio waves can give clues about their magnets. Scientists used computers to try a simple magnet shape mixed with a more complicated one. Sometimes the clues still looked simple, and sometimes they looked messy. So a simple-looking clue does not always mean a simple magnet. But these computer magnets still could not explain all the messy clues from real pulsars.
Cheng-Liang Jiao, Liying Zhu, Xiang-dong Shi+1 more
AstronomerThis theoretical study models an optically thick, quasi-spherical accretion flow surrounding an inner disk, with disk luminosity coupled self-consistently to the accretion rate. Global transonic solutions using radiative transfer in the diffusion approximation yield a generalized Eddington luminosity limit and a saturated accretion rate typically orders of magnitude below the classical Bondi prediction. At sufficiently low densities, the inflow’s enthalpy flux contributes substantially to the emergent luminosity, reducing the inner disk luminosity and allowing an unsaturated state. The authors derive a criterion for estimating whether saturation occurs. Applied to fallback accretion in failed supernova systems, the model predicts a nearly constant emergent luminosity that could explain the observed plateau in the failed supernova candidate M31-2014-DS1. Including an inner disk also avoids the under-luminous predictions of a purely spherical fallback model extending to the central object. These are theoretical results and a proposed interpretation of the observed plateau, not confirmation of the candidate’s nature or accretion geometry.
PublicThe researchers developed a theoretical model of gas falling inward from a roughly spherical region and feeding a smaller disk near the center. Radiation from that disk acts back on the incoming gas. In the model, this interaction limits the light produced and usually restricts the gas supply to rates far below those predicted by a classical spherical-infall calculation. At sufficiently low gas densities, energy carried by the incoming gas becomes an important source of the escaping light, and the flow no longer remains in the saturated state. The model could help explain the observed period of nearly steady brightness in M31-2014-DS1, a candidate failed supernova, through gas falling back after the event. The inner disk supplies light missing from a purely spherical model. This is a possible explanation of the brightness plateau, not proof that the proposed arrangement exists in this object.
Young explorerImagine gas falling inward, with a little spinning disk near the middle. Scientists made a model in which light from the disk pushes back on the falling gas and limits how much can fall in. The model suggests that this could make the light stay nearly steady for a while. Astronomers have seen nearly steady light from something that may be a star whose explosion failed. This idea might explain it, but they do not know for sure.
A. Akhmetali, Y. S. Abylkairov, J. A. Font+2 more
AstronomerThis study extends machine-learning classification of the dense-matter equation of state (EOS) in rapidly rotating core-collapse supernovae from individual gravitational-wave detectors to detector networks. Convolutional neural networks classify 10 EOS classes directly from noisy detector data in tests of second- and third-generation observatories, exploring network configuration, source distance, arrival time, and sky location. These performance tests, rather than reported supernova detections, indicate that network geometry strongly affects classification. Current networks show promising performance for Galactic sources, but their reach depends sensitively on the network antenna response. Adding detectors improves time-averaged performance and sky uniformity. Third-generation observatories extend the tested classification reach to 100 kpc for favorable source orientations, without eliminating geometric dependence.
PublicGravitational waves from collapsing stars might help reveal how matter behaves at the extreme densities inside atomic nuclei. This study tests whether machine learning could distinguish 10 descriptions of that matter using noisy signals from networks of gravitational-wave detectors, focusing on rapidly rotating stellar collapses. The findings concern classification tests, not measurements from an observed supernova. Networks of current detectors show promise for events within our Galaxy, but success depends strongly on how the detectors are arranged and how well they respond to a source in a particular direction at a particular time. Adding detectors improves average performance and makes coverage more even across the sky. Tests of next-generation observatories indicate that classification could reach 100 kiloparsecs for favorably oriented sources, though detector geometry would still matter.
Young explorerWhen a big, fast-spinning star collapses, it may send out tiny ripples in space. Scientists tested a computer helper to see whether detectors catching those ripples could help choose among 10 ideas about how tightly squeezed matter behaves. They did not report catching a real exploding star this way. Their tests suggest that using more detectors helps, but where the star is and how the detectors are placed still matter. Future detectors could help with stars much farther away, if they are facing a helpful way.
Yuya Kawabata, Takaaki Tanaka, Hiromasa Suzuki+1 more
AstronomerArchival Chandra observations reveal numerous synchrotron X-ray hotspots extending upstream of the supernova remnant RX J1713.7−3946. Their spatial and temporal properties are consistent with emission from secondary electrons produced by interactions between accelerated protons and dense molecular clumps, rather than establishing that origin uniquely. Using the upstream hotspot extent, the authors estimate a proton diffusion length of approximately 1 pc and infer an upstream magnetic field of approximately 10 μG. This field constraint is consistent with recent simulations of Bell-instability-driven amplification. The authors conclude that the current amplification is insufficient for PeV acceleration, interpreting this as an explanation for the observed TeV gamma-ray spectral cutoff and proposing the approach as a diagnostic of PeVatron capability in stellar shocks. The origin of Galactic cosmic rays up to the knee remains unresolved.
PublicWhere our Galaxy’s most energetic cosmic rays come from remains an open question. In archived Chandra observations, researchers found many X-ray bright spots extending ahead of the shock wave of the exploded star’s remnant RX J1713.7−3946. The spots’ locations and changes over time fit an explanation in which accelerated protons collide with dense gas clumps, producing electrons that emit X-rays in magnetic fields. Using that interpretation and the spots’ extent, the researchers estimated how far the protons spread ahead of the shock and inferred the magnetic field there. The inferred field agrees with recent computer simulations of magnetic-field strengthening, but the authors conclude that the present strengthening is too weak to accelerate particles to the petaelectronvolt energies of the cosmic-ray knee. They interpret this as explaining the remnant’s observed gamma-ray cutoff and suggest that similar observations could help assess other stellar shocks.
Young explorerScientists found little X-ray bright spots ahead of a wave from an exploded star. They think tiny particles may be bumping into thick clouds of gas and making the spots shine. If that idea is right, the spots help them work out how strong the magnetic field is there. They think it is not strong enough right now to help particles reach the very high energies they are looking for. The spots could help scientists check other star explosions, too.
Tuomas Kangas, Takashi Nagao, Uliana Pylypenko+2 more
AstronomerThis study characterizes circumstellar material (CSM) around broad-lined, hydrogen-rich superluminous supernovae using blackbody fits to spectral energy distributions, UV-excess evolution, late-time line profiles, and public WISE images. Interpreting the UV excess as interaction emission yields mass-loss rates of approximately 10^-4–0.03 solar masses per year under the assumption that all interaction luminosity emerges in the UV; these are conservative lower limits on the total mass-loss rates. Radii inferred from late-time line velocities are mostly too large for a spherical interaction photosphere and are compatible with the blackbody-radius evolution only for non-spherical CSM with a low filling factor. In some cases, discrepancies between spectroscopic and blackbody expansion velocities further support this interpretation. The sample shows considerable diversity, attributed tentatively to differing viewing angles and CSM masses. WISE images appear too shallow to detect IR echoes beyond roughly z = 0.1, while a likely echo in the nearest event, SN 2020jhm, suggests pre-existing dust.
PublicResearchers studied exceptionally bright, hydrogen-rich stellar explosions to investigate the material surrounding them. They measured ultraviolet light above what a simple thermal model predicts and examined how spectral features and the apparent emitting size changed. If the extra ultraviolet light comes from the explosion colliding with surrounding material, it implies substantial earlier mass loss from the star. The inferred rates are lower limits because the collision may also produce light outside the ultraviolet. Comparing the spectral measurements with the emitting size suggests that the surrounding material is not a uniform spherical shell, but occupies only a small fraction of the surrounding space. The explosions differ considerably; viewing angle and the amount of surrounding material are possible explanations. Infrared images were generally not sensitive enough to reveal dust echoes in more distant events, but a likely echo around SN 2020jhm suggests that dust was already present before the explosion.
Young explorerWhen a star explodes, its light can help us learn what was around it. Scientists looked at some very bright explosions and found extra light of a kind our eyes cannot see. They think this light may come from the explosion bumping into gas the star had shed earlier. Their clues suggest that the gas is not spread evenly around the star like a round shell. The explosions also look different from one another, perhaps because they have different amounts of gas or because we see them from different sides. Around one explosion, the scientists found what may be a heat echo from dust that was there before the star exploded.
Jui-An Hsu, Patrick Weltevrede, Geoff Wright+3 more
AstronomerUsing Thousand-Pulsar-Array data, the authors identify three coexisting subpulse-modulation periodicities in both profile components of PSR J1901-0906 that obey a beat relation. Fourier phase correlations in two-dimensional fluctuation spectra reveal additional spectral beat features arising from modulation of these periodicities. Single-pulse polarization states are synchronized with all three total-intensity periodicities; the authors report this as the only known case of such synchronization involving multiple coexisting periodicities. The beat system resembles that of PSR J1514-4834 but is more complex, with higher-order harmonics contributing significantly. The authors interpret the linked periodicities as evidence for an interconnected magnetospheric system. Within the geometric framework previously applied to PSR J1514-4834, a feedback model of interacting rotating carousels reproduces the observed modulation and explains the beat relations, but this model agreement does not directly establish the physical mechanism.
PublicObservations of the pulsar PSR J1901-0906 reveal three repeating patterns in the changing strength of its radio pulses. These patterns are linked by a beat relationship, analogous to the combined rhythm of overlapping musical notes, and additional beat features are also detected. The polarization of individual pulses—the orientation of their radio waves—changes in step with all three patterns. The authors report that this is the only known pulsar where such synchronization involves several coexisting repeating patterns. They interpret the linked rhythms as signs of a connected system in the pulsar's magnetic surroundings. A model involving interacting rotating patterns, described as carousels, reproduces the complex rhythms through feedback. This provides a possible explanation, rather than direct proof of what produces them.
Young explorerA pulsar is a star that spins and sends us radio signals. Scientists found three repeating rhythms in one pulsar's signals, all linked together like beats in a song. Another feature of the signals also changes in time with those rhythms. The scientists made a model with spinning patterns that affect each other, like connected merry-go-rounds. It can copy the rhythms they found, but that does not mean they know for sure what is happening around the star.
Dillon Hasenour, Paul Duffell, Abigail Polin
AstronomerThis study presents thermonuclear hydrodynamic simulations of the double-detonation model for sub-Chandrasekhar-mass white dwarfs with thin to thick helium shells. Calculations use the newly introduced moving-mesh nuclear hydrodynamics code Cattails, followed by radiative transfer with Sedona. Thin-shell models yield light curves and spectra consistent with normal Type Ia supernovae. Thicker-shell models show early luminosity bumps powered by radioactive shell ashes and early color reddening resembling features sometimes observed in peculiar Type I supernovae. In the models, reddening arises from line blanketing by heavy elements produced in the shell detonation and surrounding the central emission. The study relates reddening time to initial helium-shell mass, examines how this relation varies with total mass, and considers the dependence of peak brightness on total mass. Fitting functions provide estimates of shell masses consistent with observed early reddening within this model framework; they do not establish double detonation as the origin of Type Ia supernovae.
PublicType Ia supernovae help astronomers measure cosmic distances and enrich galaxies with chemical elements, but their origins remain uncertain. This study uses computer simulations to explore one promising explanation: double-detonation explosions of white dwarfs with helium shells. Models with thin shells produce brightness changes and patterns of emitted light consistent with ordinary Type Ia supernovae. Models with thicker shells produce an early extra brightening from radioactive material and an early shift toward redder colors, resembling features sometimes seen in unusual Type I supernovae. In the simulations, heavy elements made in the shell explosion block parts of the light, causing the reddening. The researchers provide formulas for estimating which helium-shell masses could fit an observed early color change, while accounting for the model's total mass. These are model-based estimates, not proof of how a particular supernova exploded.
Young explorerSome exploding stars help scientists learn how far away things are in space. But scientists are still figuring out what makes these stars explode. Here, they used computers to try out explosions of stars with thin or thick coats of helium. Thin coats made pretend explosions that looked like common ones. Thick coats made an extra flash early on and made the light look redder because material in the coat blocked some colors. The scientists made rules to help guess how thick a real star's coat might have been. The computer tests give clues, but they do not prove what happened.
Claudio Galelli, Alessandro Testi, Lorenzo Caccianiga
AstronomerThe INFN PRImuS experiment presents a pipeline for recovering calibrated track-length spectra from mineral paleo-detectors, combining sample preparation, automated multi-focus optical microscopy, the two-stage OptimusPrimus machine-learning algorithm, and a forward-folding model. The model propagates geometric sectioning, etching, and the measured detection response into simulated spectra for comparison with data. Validation on chemically etched obsidian yielded a recovered track-length distribution statistically compatible with expert annotation. The team also developed and characterized dry argon-plasma etching for halite, a mineral of interest for low-background cosmic-ray paleo-detection. Application to plasma-etched halite is underway with the aim of identifying cosmic-ray-induced tracks; such identification is not reported here. Although the pipeline stages are mineral-agnostic, the trained networks and detection response must be re-derived from annotated data for each mineral.
PublicNatural minerals may preserve tiny damage trails left by energetic particles over geological time, potentially providing a record of past cosmic rays. This study addresses a practical challenge: turning microscope images of those trails into reliable measurements of their lengths that can be compared with theoretical predictions. The researchers developed a workflow using automated microscopy, machine learning, and simulations that account for how sample preparation and detection affect the measurements. In tests on chemically etched obsidian, the measured distribution of trail lengths was statistically consistent with expert assessments. They also developed and characterized a plasma-etching method for halite and are now applying the workflow to it to look for cosmic-ray trails. The abstract does not yet report identifying those trails in halite or reconstructing a past cosmic-ray history.
Young explorerTiny particles from space can leave tiny trails inside rocks. Scientists hope to use those trails to learn about particles that passed through long ago. This team made a way to prepare rocks, take microscope pictures, and teach a computer to find and measure the trails. In a rock called obsidian, the computer's measurements agreed with those of expert people. The team also made a way to prepare a mineral called halite. Now they are looking in it for trails made by particles from space, but they have not yet reported finding them.
Muad Ghaith, Khaled Obaideen
AstronomerThis critical review synthesizes peer-reviewed indirect dark-matter searches from January 2000 through October 2026 using a structured search strategy. Its assessment connects particle interactions and halo source terms to propagation or cosmological energy deposition, instrumental response, background modeling, and statistical inference. Fermi-LAT dwarf-spheroidal observations provide robust GeV-scale annihilation benchmarks; Galactic-center searches have higher expected signals but greater foreground and halo-profile dependence. Precise charged-cosmic-ray measurements remain limited by propagation and source uncertainties, while neutrinos provide complementary sensitivity through solar capture, directional and flavor information, and high-mass annihilation or decay. The review regards the 3.5 keV line, 511 keV emission, Galactic-center GeV excess, charged-particle features, cluster radio excesses, and candidate gamma-ray lines as inconclusive, citing confirmation, target-scaling, spectral-degeneracy, or background-modeling limitations. CMB energy-injection limits and 21 cm measurements add complementary cosmological constraints. AI-assisted reconstruction and inference require rigorous calibration and domain-shift validation. The proposed strongest discovery standard is statistically consistent evidence across independent targets, instruments, or messengers under common particle-physics parameters and well-characterized uncertainties, not any single reported anomaly.
PublicThis review compares searches for signals that dark-matter particles might produce when they interact or decay. It covers several kinds of radiation and particles, as well as observations of the early universe. Gamma-ray observations of dwarf galaxies provide particularly robust limits on dark-matter annihilation. Searches toward the center of our galaxy could yield stronger signals, but interpreting them depends more heavily on uncertain backgrounds and the distribution of dark matter. Several much-discussed signals remain inconclusive: other explanations, uncertain modeling, or insufficient independent confirmation prevent a firm dark-matter interpretation. Artificial intelligence can help analyze observations, but its reliability needs careful testing. The review argues that the strongest discovery case would combine independent observations that agree on the same dark-matter explanation, with uncertainties clearly accounted for.
Young explorerScientists look for light and tiny particles that dark matter might make. This review compares many of those searches. Some clues look interesting, but scientists still cannot be sure they come from dark matter rather than something else. Looking at dwarf galaxies gives especially dependable limits on what dark matter could do. The strongest clue would be several different searches finding signals that fit the same explanation.
Mudit Garg, Yan-Fei Jiang
AstronomerMatched 3D global Athena++ simulations compare alpha-viscosity hydrodynamics with MRI-driven magnetohydrodynamics in a locally isothermal circumbinary disk around an equal-mass, circular massive black hole binary. Identical initial tori and grids isolate the transport prescription; excising r < 2 times the binary separation permits 1000 binary orbits of evolution. Both disks have the same accretion rate and exert positive outer-disk torques, but the MHD torque is 3.5 times larger and three times more variable. Near-midplane transport is similar in the disk body but three times weaker at the MHD cavity edge, where 2–3 times more mass accumulates in a more eccentric cavity, increasing the torque. HD accretion varies mainly at twice the binary frequency, whereas a persistent cavity-edge lump and its beat with the binary modulate MHD accretion. The authors infer a 3.5-fold larger outer-disk contribution to the gas-induced gravitational-wave phase shift for LISA binaries and a different variability signature for LSST and Roman. These are simulation-based implications, not detections; the excluded inner region means the reported torque is not the total gas torque.
PublicComputer simulations suggest that magnetic turbulence can substantially change how a surrounding gas disk pushes on a pair of massive black holes. The researchers compared a magnetic model with a commonly used simplified model of gas transport. Both supplied gas at the same rate, but gas outside the central excluded region produced a torque—a twisting push—that was 3.5 times stronger and three times more variable in the magnetic simulation. More gas accumulated along a more elongated inner edge of the magnetic disk, and its feeding rhythm also differed. The authors infer that this outer gas could make a larger contribution to changes in gravitational-wave timing measured by LISA, with a different variability pattern relevant to LSST and Roman. These are predictions from simulations, not observations, and the gas closest to the black holes was not simulated.
Young explorerScientists used computers to pretend that two black holes were circling inside a ring of gas. When they included magnetic effects, the gas gave the pair a stronger, more wobbly twisting push. This might change signals we could look for, but it is not something they watched happen in space, and their model left out the closest gas.
L. Vleeschower, R. Sengar, L. Nieder+17 more
AstronomerPSR J2147-3604 is a fully recycled 3.2-ms pulsar discovered through reprocessing of the 350-MHz GBNCC survey and independently confirmed serendipitously by MeerKAT TRAPUM. One year of phase-connected Murriyang/Parkes timing establishes a 4.5-day binary orbit with eccentricity approximately 1.9 × 10^-5. Gamma-ray pulsations found in Fermi-LAT data enabled joint radio and gamma-ray timing. Assuming a neutron-star mass of 1.5 solar masses, the inferred median companion mass is approximately 0.2 solar masses, consistent with a helium white dwarf but not establishing that identification. The dispersion measure is 17.0 pc cm^-3, and strong scintillation accompanies a detection fraction of approximately 72% in Murriyang observations at 704–1174 MHz. A narrow duty cycle of approximately 6.5% yields individual arrival-time uncertainties of approximately 4.5 microseconds for 10-minute MeerKAT integrations, suggesting suitability for pulsar timing arrays rather than demonstrating performance in an array.
PublicAstronomers discovered PSR J2147-3604, a pulsar that spins once every 3.2 milliseconds, by reprocessing a radio survey. Another radio survey independently picked it up, and a search of Fermi-LAT data also revealed gamma-ray pulses. A year of radio timing showed that the pulsar circles a companion every 4.5 days in an almost circular orbit. If the pulsar has an assumed mass of 1.5 times the Sun’s, the inferred typical companion mass is about one-fifth of the Sun’s, compatible with a helium white dwarf; the companion’s identity is not confirmed. Its radio signal fluctuates strongly, and it was detected in about 72% of observations in one radio band. Its narrow pulses allowed arrival-time measurements with uncertainties of about 4.5 millionths of a second in 10-minute MeerKAT observations. That precision makes it a promising candidate for pulsar timing arrays, not yet a demonstrated array result.
Young explorerAstronomers found a tiny star that spins very fast and sends out flashes like a lighthouse. It goes around another object about every four and a half days, following a path that is nearly a circle. The other object might be a small leftover star called a white dwarf, but the scientists are not sure. The radio flashes sometimes become hard to spot. When they are clear, scientists can measure their timing very carefully, so this star might be useful in a team of space clocks.
Changhyun Cho, David M. Russell, Aaryan Sharma+8 more
AstronomerUsing quasi-simultaneous optical and X-ray data for black hole low-mass X-ray binaries and AGN with optical disk-radius estimates, the study finds a tight correlation spanning stellar-mass to supermassive black holes. Optical/X-ray reverberation lags provide a proxy for the reprocessing radius, a_R, allowing comparison across structurally different systems. The fitted relation is log L_V = 0.48 log L_X + 0.96 log a_R + 6.5, with approximately 0.20 dex scatter, reduced to 0.18 dex by a cos i disk-inclination correction. This is consistent with extending the approximately square-root optical/X-ray scaling in X-ray binaries to AGN. The authors interpret the correlation as evidence suggesting scale-invariant X-ray reprocessing, rather than definitive proof of that mechanism, and as a constraint on models of X-ray emission regions.
PublicThe researchers compared optical light and X-rays from material surrounding both stellar-mass and supermassive black holes. Using the delay between X-ray and optical variations to estimate the size of the region that reprocesses radiation, they found a tight relationship: optical brightness increases with X-ray brightness and with the estimated size of that region. Accounting for the disk's viewing angle slightly tightened the relationship. The finding suggests that disks around black holes of very different masses may turn absorbed X-rays into optical light in a similar way. This is an interpretation of the measured correlation, not proof that reprocessing explains all the optical light.
Young explorerScientists looked at light from disks of material around smaller and much bigger black holes. They found a pattern linking the X-rays, the light our eyes can see, and how big the light-making part of the disk seems to be. They used the waiting time between changes in the two kinds of light to help estimate that size. The pattern is a clue that these disks may catch X-rays and shine back with visible light in a similar way, even around very different-sized black holes.
R. Sengar, L. Vleeschower, D. L. Kaplan+13 more
AstronomerA reanalysis of the 350-MHz Green Bank North Celestial Cap survey, observed with the Green Bank Telescope during 2009–2020 at declinations above −40°, confirmed 51 new pulsars from 60 promising FFT-search candidates using Green Bank and CHIME. Candidate selection extended to very low spectral signal-to-noise ratios, with up to 32 harmonics summed. A direct folding search over periods of 500 ms–10 s recovered all 43 FFT discoveries in that range and found one additional pulsar missed during FFT-candidate inspection. Most discoveries are canonical pulsars, with periods of 299 ms–4.4 s and dispersion measures of 10–192 pc cm^-3; a binary millisecond pulsar has a 3.2-ms spin period and a 4.5-day orbit. The reanalysis redetected 855 pulsars, including 825 in the FFT search. Within its effective parameter space, the FFT search recovered approximately 98% of known pulsars within the survey sensitivity limits. Accounting for previously reported pulsars with unprocessed observations or parameters outside the search range brings the updated survey census to 964 pulsars.
PublicSearching existing radio observations again revealed pulsars that earlier analysis had missed. The team reexamined Green Bank North Celestial Cap survey data collected from 2009 to 2020 and confirmed 51 new pulsars using Green Bank and CHIME. A second search method, aimed at slower-spinning pulsars, recovered all 43 of those discoveries within its targeted period range and found one more pulsar overlooked during inspection of the first search’s candidates. Most discoveries spin once every 299 milliseconds to 4.4 seconds; the team also found a much faster pulsar spinning every 3.2 milliseconds in a binary system with a 4.5-day orbit. The first search recovered about 98% of known pulsars that were both detectable at the survey’s sensitivity and within the search’s effective range—not 98% of all pulsars in the surveyed sky. The updated survey census, including previously reported pulsars, totals 964.
Young explorerScientists looked again at old recordings from a radio telescope to find spinning stars called pulsars. Their first search helped them confirm 51 new pulsars. Then they tried another way of searching and spotted one more that had been overlooked. Most of the new ones spin more slowly, but one spins super fast and has a companion. Looking again, in a different way, helped the scientists find things they had missed.
Qian-Qi Ma, Wei-Min Gu, Shan-Shan Weng+1 more
AstronomerThe study compares X-ray radiative efficiencies in five ultra-compact X-ray binaries in globular clusters, with orbital periods below 40 minutes and identified neutron-star or black-hole accretors. The authors derive accretion rates using the dominance of gravitational radiation in driving orbital angular-momentum loss, then combine these rates with X-ray luminosities. They find black-hole systems to be about two to three orders of magnitude less radiatively efficient than neutron-star systems. They interpret this difference as evidence that accretion energy is swallowed by black holes, providing an indirect probe of stellar-mass black-hole event horizons rather than a direct detection.
PublicResearchers studied five tightly orbiting pairs of stars in globular clusters, each containing either a neutron star or a black hole that receives matter from its companion. All five pairs complete an orbit in less than 40 minutes. Using gravitational radiation to estimate how quickly matter is supplied, the team calculated how efficiently that matter's energy becomes X-rays. The black-hole systems were about 100 to 1,000 times less efficient than the neutron-star systems. The authors interpret the missing radiation as a sign that energy is carried into the black holes, supporting the presence of an event horizon—the boundary beyond which light cannot escape. This is indirect evidence, not a direct observation of that boundary.
Young explorerScientists looked at five pairs of objects in space. In each pair, a black hole or a neutron star takes in stuff from its partner. They worked out how much stuff goes in and compared it with how much X-ray light comes out. The black-hole pairs made much less light for the stuff they took in. Scientists think this is a clue that black holes swallow energy past a boundary where light cannot get out. They did not see that boundary itself.
Parameswaran Ajith
AstronomerThis review assesses the prospective role of gravitational-wave observations in addressing open questions in astrophysics and cosmology. A decade after the first direct detection, progressive detector upgrades and anticipated space-based and next-generation ground-based observatories are expected to extend observational reach to cosmological redshifts and substantially broaden frequency coverage, enabling access to source classes beyond current detectors. The authors survey current understanding of the source landscape and discuss possible future discoveries, including unexpected sources or phenomena. These are prospects, not reported detections; the abstract provides no specific measurements or quantitative forecasts.
PublicThis review looks at how future observations of gravitational waves could help answer unresolved questions about the universe. Gravitational waves have already been directly detected, but improved detectors and planned observatories in space and on the ground are expected to reach much farther into the universe and detect a wider range of wave frequencies. That could reveal kinds of sources today's detectors cannot observe. The authors summarize what is currently understood and explore what might be discovered next, while noting that surprises are likely. The article describes future possibilities rather than announcing new observations.
Young explorerScientists have already found waves that travel through space. This article talks about how better wave detectors, including ones scientists hope to put in space, could help us find waves from much farther away and catch kinds of waves we cannot catch now. They might help us learn new things about the universe—even surprising things! These are things scientists hope to discover, not new things they have found yet.
H. Yuan, Q. A. Parker, M. A. Guerrero
AstronomerThe first targeted Einstein Probe observations of a planetary nebula detect central-region X-ray emission in IC 1297 with the Follow-up X-ray Telescope. Spectral fitting gives kT = 0.086 (+0.054, −0.058) keV, or approximately one million K, and an absorption-corrected 0.3–2.0 keV luminosity of 2.8 × 10^32 erg/s. These properties are consistent with a shocked-wind hot bubble; there is no evidence for X-ray emission from the Wolf-Rayet central star itself. At the adopted distance of approximately 3.8 kpc, IC 1297 is the most distant known X-ray-emitting planetary nebula and among the most luminous. A compilation of all 41 known Galactic X-ray-emitting planetary nebulae shows a distance–luminosity correlation attributed to detection bias toward brighter sources at greater distances. It also shows a luminosity separation between bubbles powered by H-rich and [WR]-type central stars, with the latter reaching luminosities up to an order of magnitude higher. The ten most luminous objects host [WR]/PG 1159 central stars.
PublicEinstein Probe has detected X-rays from the central region of IC 1297, a planetary nebula: a cloud of gas around an aging star. The measured spectrum indicates gas at roughly one million degrees, consistent with a hot bubble produced by shocked stellar winds. The observations do not provide evidence that the central Wolf-Rayet star itself emits X-rays. Using an assumed distance of about 3.8 kiloparsecs, the researchers identify IC 1297 as the most distant known X-ray-emitting planetary nebula and one of the brightest in intrinsic X-ray output. Their comparison of all 41 known examples in our Galaxy also highlights a selection effect: at greater distances, the brightest sources are easier to detect. Nebulae with [WR]-type central stars can have hot bubbles up to ten times as luminous as those around hydrogen-rich stars, and all ten of the most X-ray-luminous examples have [WR] or PG 1159 central stars.
Young explorerAstronomers used a space telescope to find X-rays, a kind of light our eyes cannot see, inside a gas cloud called IC 1297. The light suggests that some gas is about a million degrees hot. It may be a hot bubble made when wind from the star crashes into other gas, rather than light coming from the star itself. If the cloud is as far away as the researchers think, it is the farthest cloud of this kind found shining in X-rays. Faraway clouds are harder to spot unless they shine very brightly.
Lorenzo Ducci, Sandro Mereghetti, Ciro Pinto+8 more
AstronomerFour XMM-Newton observations near periastron in 2025, MAXI and REM monitoring, and reanalysed RXTE data probe renewed activity in the Be/X-ray binary A0538-66 in the Large Magellanic Cloud. On 30 September 2025, its 0.2–10 keV luminosity reached approximately 1.5 × 10^39 erg/s, the highest since 1980; MAXI detected similarly bright outbursts in February, May, and August 2026. The September XMM-Newton observation yielded a spin period of 69.25878(2) ms and a period derivative of 6.58(9) × 10^-10 s/s. Pulsations had a low, energy-dependent pulsed fraction, approximately 3% in 1–10 keV, with soft and hard profiles offset by half a cycle. Archival RXTE data reveal a shorter period, 68.88813(28) ms, on 3 December 1998. RGS spectra show stationary photoionised emission and blueshifted absorption implying an outflow at approximately 0.12c. The authors infer highly super-Eddington accretion and an intrinsic luminosity near 1.5 × 10^39 erg/s, identifying the system as a transient ultraluminous X-ray pulsar. Since 2023, REM optical bursts have lengthened and brightened, but most lack an X-ray counterpart above 10^37 erg/s. The proposed interpretation is intermittent screening of the innermost emission by a geometrically thick, radiation-pressure-dominated inner accretion disc.
PublicA0538-66, a binary system in the Large Magellanic Cloud, contains a neutron star spinning roughly once every 69 milliseconds. On 30 September 2025, astronomers observed its brightest X-ray activity since 1980, with similarly bright outbursts detected in 2026. They also measured weak X-ray pulses and found spectral evidence for gas flowing outward at about 12% of the speed of light. The researchers infer an exceptionally high rate of gas accretion, identifying the system as one of the few known transient ultraluminous X-ray pulsars. Its visible-light bursts have become longer and brighter since 2023, yet most have no comparably luminous X-ray counterpart. To explain the observations, the authors suggest that thick inner regions of the gas disc sometimes block our view of the central emission; this is an interpretation rather than a directly observed obstruction.
Young explorerAstronomers watched a very fast-spinning star in a pair of stars. It became very bright in X-rays, a kind of light our eyes cannot see. They also found signs of gas rushing away. The pair makes bright flashes of ordinary light, but most do not come with strong X-ray flashes. The scientists think thick gas around the spinning star may sometimes hide its bright middle.
Ting Yu, Zhifu Gao, Zhongli Zhang+1 more
AstronomerMurchison Widefield Array observations of six pulsars at 80–240 MHz, combined with literature flux densities and pulse-profile modelling, test whether a smooth Gum Nebula can account for spectral turnovers and scattering. All six spectra depart from a single power law. Free–free absorption (FFA) is favoured for J0737-3039A and J0820-4114, while turnover-constrained broken power laws are favoured for J0742-2822 and J0835-4510; the remaining classifications depend on assumed error floors. Conditional on FFA, inferred emission measures of 10^4–10^5 pc cm^-6 at electron temperatures of 3,000–10,000 K greatly exceed smooth-shell expectations. Scattering is consistent with a frequency exponent of −4 for J0737-3039A and J0837-4135; fitted exponents are −3.07 ± 0.11 for J0742-2822 and −1.59 ± 0.44 for J0820-4114, the latter using a joint two-component model. Vela is best described by an effective thick-screen model with an exponent of approximately −2.74. Neither tested Galactic electron-density model uniformly matches both independent distances and low-frequency scattering. The findings favour a structured Gum–Vela magneto-ionic environment, with absorption and scattering not necessarily arising in the same plasma component.
PublicResearchers studied radio signals from six pulsars along different paths through the nearby Gum Nebula region. Combining low-frequency observations with earlier measurements, they found that none of the six pulsars follows a single simple rule for how radio brightness changes with frequency. Models favour absorption by ionised gas for two pulsars and a change in spectral slope for two others; the remaining two classifications depend on assumptions about measurement uncertainties. If absorption explains the spectral changes, the inferred gas properties are far beyond what a smooth nebular shell would predict. The team also modelled how intervening material spreads out the radio pulses, finding different frequency dependences along different paths. Neither of two tested models of the Galaxy’s free electrons consistently explains both the independently measured pulsar distances and the pulse spreading. Together, the findings favour an uneven Gum–Vela environment rather than a smooth one. The material absorbing the signals need not be the same material spreading the pulses.
Young explorerPulsars send out radio pulses like ticking space clocks. Scientists studied signals from six of them that travel through a big cloud of gas. Some radio signals were weaker, and some pulses were more spread out. The scientists compared different explanations. Their results suggest that the cloud is patchy, not smooth, so signals taking different paths meet different gas. But they are not sure of every detail, and the gas that weakens a signal might not be the same gas that spreads out its pulses.
Jan Benáček, Benoît Cerutti, Martin Pohl+2 more
AstronomerThe authors present a three-dimensional particle-in-cell simulation of a binary neutron-star magnetosphere with physically orbiting stars, allowing orbital motion itself to twist magnetic loops. In the simulation, the ratio of stellar magnetic-field strengths controls flare emergence, while stellar spins determine flare direction and modulation. Four distinct regions of strong electromagnetic energy release are identified: an expanding fast magnetosonic wave that steepens into a monster shock, a plasma flare, an expanding fireball that pushes the flare, and a reconnecting current sheet within the flare. The wave is released when orbital motion cuts a closed plasma loop; its electric and magnetic amplitudes are comparable and reach the background magnetic-field amplitude. The authors identify this wave as a promising source of coherent radio emission, not as a demonstrated fast radio burst. The simulated particle spectra and plasma structures provide inputs for assessing coherent emission in kinetic-scale simulations. Orbital motion thus supplies a driving mechanism distinct from spin-driven magnetospheric twisting.
PublicCould merging neutron stars produce fast radio bursts? This study explores a possible mechanism using a three-dimensional computer simulation, rather than observations of a burst. As two neutron stars orbit one another, their motion twists loops in their interacting magnetic surroundings. In the simulation, the relative strengths of the stars’ magnetic fields govern whether flares emerge, while their spins control the flares’ direction and variation. The researchers find several regions where electromagnetic energy is released, including a wave that grows into a strong shock and a flare pushed by an expanding fireball. They propose that the wave, released when orbital motion cuts a closed plasma loop, could generate coherent radio emission. Whether it actually produces a fast radio burst remains to be assessed. The work highlights orbital motion as an energy driver distinct from the stars’ own spinning.
Young explorerThe scientists made a computer model of two tiny, very dense stars going around each other. The stars have magnetic loops around them. In the model, going around each other twists those loops and can make flares. When their motion cuts a loop, a powerful wave comes out. The scientists think this wave might help make a sudden flash of radio waves, but they have not shown that it does.
Kazuya Iwata, Keiichi Maeda, Ken J. Shen
AstronomerThis theoretical study extends cell-based detonation criteria, originally developed for terrestrial burning and previously applied to pure helium in white-dwarf envelopes, to helium–carbon and carbon–oxygen mixtures relevant to double-detonation models of type Ia supernovae. Predictions for minimum initiation energy and critical stellar mass for stable propagation agree satisfactorily with previous hydrodynamic studies. The analysis supports stable helium–carbon detonation in an envelope of approximately 10^-3 solar masses, identifies the oxygen-scale cell width as a useful diagnostic for carbon–oxygen detonation, and indicates that direct initiation of carbon–oxygen detonation requires a white dwarf heavier than 0.6 solar masses. These are theoretical findings, not astronomical detections; the mass restriction concerns direct initiation specifically. The approach offers a simple first-order calibration of explosion models using an analogy with terrestrial detonation that can be tested in laboratory experiments.
PublicHow an explosive nuclear-burning wave starts and keeps moving through a white dwarf remains an unresolved problem in understanding type Ia supernovae. This study adapts theories of the cellular patterns in Earth-based detonations to helium–carbon and carbon–oxygen fuel in white dwarfs. Its calculations agree satisfactorily with earlier computer studies of the energy needed to start a detonation and the stellar mass needed to sustain it. The theory suggests that a helium–carbon layer containing about one-thousandth of the Sun’s mass can sustain a detonation. It also indicates that starting a carbon–oxygen detonation directly requires a white dwarf more massive than 0.6 times the Sun. These are theoretical conclusions, not observations of exploding stars. The method could help researchers make initial checks of explosion models through relatively simple calculations linked to laboratory-testable burning physics.
Young explorerScientists want to understand how a small star called a white dwarf can start a big explosion and keep it going. They used ideas about explosions on Earth to calculate what might happen inside these stars. Their calculations suggest that even a very thin layer of certain star ingredients could keep an explosion wave moving. Another mix of ingredients seems to need a heavier star for the wave to start directly. The answers fit earlier computer studies fairly well, but the scientists did not watch these things happen in a real star.
C. Ballocco, A. Miraval Zanon, A. Papitto+25 more
AstronomerA coordinated timing study of the accreting millisecond pulsar SAX J1808.4-3658 during its 2022 outburst and quiescence detects coherent optical pulsations in outburst with a pulsed luminosity of 1.3 × 10^30 erg/s. Together with previous detections, the results suggest increasing optical pulsed amplitude as X-ray flux decreases; optical and X-ray pulsed luminosities exhibit opposite trends with X-ray luminosity. X-ray-to-optical delays of 0.88 ± 0.04 ms and 0.51 ± 0.03 ms in two outburst observations demonstrate variable relative timing. These findings and the spectral energy distribution support, rather than establish, distinct origins: non-thermal emission from relativistic particles for the optical pulses and channeled accretion onto the neutron-star surface for the X-ray pulses. In quiescence, no coherent optical pulsations are detected, with a 95% confidence upper limit of 2.2 × 10^29 erg/s on pulsed luminosity, corresponding to an optical efficiency comparable to those of spider radio millisecond pulsars. Simultaneous MeerKAT observations detect no radio pulsations down to approximately 10 μJy, tightening constraints without excluding an active rotation-powered pulsar obscured at radio wavelengths by intra-binary material.
PublicAstronomers studied the rapidly spinning neutron star SAX J1808.4-3658 during a 2022 outburst, when it was drawing in material, and during a quiet period. They detected regular visible-light pulses during the outburst. Combined with earlier detections, the observations suggest that the visible-light pulses grow stronger as the X-ray brightness falls, while the X-ray pulses follow the opposite trend. The measured delay between X-ray and visible-light pulses also changed between two observations. Together with the distribution of emission across wavelengths, this supports the interpretation that the two kinds of pulses have different origins: fast-moving particles may produce the visible light, while infalling material guided onto the star's surface produces the X-rays. Neither visible-light nor radio pulses were detected in the quiet period. The radio nondetection does not rule out a pulsar powered by its rotation, because material within the binary system could absorb its radio signals.
Young explorerAstronomers watched a tiny, fast-spinning star while it was taking in material and having a bright spell. They saw it blink in ordinary light and in X-rays, a kind of light our eyes cannot see. The time between the two kinds of blinks changed. The clues suggest that speedy particles make the ordinary-light blinks, while material landing on the star makes the X-ray blinks. When the star was quiet, the team could not find ordinary-light or radio blinks. Radio blinks might still be there, hidden by material around the star.
Reilly Tom, Paolo Desiati, Juan Carlos Díaz-Vélez+1 more
AstronomerGround-based observations detect cosmic-ray anisotropy, but heliospheric magnetic deflections complicate inference of its interstellar distribution. The authors constructed a simulated transport model that backtracks antiprotons from Earth into the interstellar medium and represents energy-dependent spatial transfer probabilities with HEALPix maps. The transfer matrices are singular, requiring singular-value-decomposition regularization for inversion. Loss of the equatorial North-South anisotropy component in ground-based observations severely degrades map recovery. In their reconstruction tests, a geometric circle-fitting algorithm estimates and restores this component, improving recovery of the interstellar dipole structure. The study also finds that Poisson fluctuations in detected event counts dominate matrix-transformation errors when counts are spread over multiple energies. These are modeling and reconstruction results, not a direct measurement of the recovered interstellar distribution.
PublicExperiments on Earth detect an uneven pattern in the arrival directions of cosmic rays, but magnetic fields around the Sun bend their paths and make the original pattern difficult to infer. The researchers built a simulation that traces antiprotons backward from Earth to interstellar space and uses the resulting probabilities to reconstruct that pattern. A major obstacle is that ground-based observations miss part of the North-South pattern. In the study's reconstruction tests, an algorithm that estimates and restores this missing information improves recovery of the broad pattern in interstellar space. The reconstruction still requires a mathematical method to handle information that cannot be uniquely recovered, and random fluctuations in event counts dominate the transformation errors when the counts are spread across multiple energies. The work demonstrates a modeling approach rather than directly observing the original interstellar pattern.
Young explorerTiny particles from space reach Earth from some directions more often than others. Magnetic fields around the Sun bend their paths, so it is hard to tell where they came from. The scientists made a computer model that follows particle paths backward. Measurements from the ground miss part of the up-and-down pattern, so the scientists made a way to guess and put that part back. In their computer tests, this helped them recover the big pattern better. It was not a direct picture of the particles far away, and random changes in how many particles are counted still make the answer uncertain.
Chen Li, Jelle S. Kaastra, Liyi Gu+7 more
AstronomerA time-resolved analysis of the Fe XXV absorption trough in NGC 3783 uses 19 XRISM/Resolve spectra from a continuous 10-day observation. Normalized equivalent widths were measured in five fixed velocity intervals; three show significant variability. Two intervals with less emission-line contamination respond differently to low- and high-flux states. Time-dependent photoionisation modelling fails to reproduce the strongest observed EW variation, significant at 3.5 sigma. Uncertainty in the assumed initial equilibrium state may explain this failure and prevents a precise density measurement. Photoionisation calculations assuming the high-density limit instead provide approximate ionisation-parameter constraints. The low-velocity component (-320 to -680 km/s) exhibits a delayed inverse response, interpreted as indicating high ionisation; its relatively short lag suggests relatively high density and an inferred distance upper limit of 0.05 pc. The high-velocity component (-680 to -1040 km/s) shows a positive response with a longer lag, suggesting lower ionisation, lower density, and an inferred distance upper limit of 0.25 pc. The low-velocity component is consistent with a failed wind because its outflow speed is below the local escape velocity; the high-velocity component is near the escape threshold. Combined with the lower-ionisation failed wind detected in 2001, these findings support, rather than establish, a multiphase failed-wind scenario in the unobscured state over more than two decades.
PublicDuring a continuous 10-day observation of NGC 3783, researchers used XRISM/Resolve to track an X-ray absorption feature produced by highly ionised iron. They separated the feature into five gas-speed ranges and found significant changes in three. Two ranges, less affected by overlapping emission, behaved differently as the source brightened and dimmed: absorption from slower gas changed in the opposite direction after a shorter delay, while absorption from faster gas changed in the same direction after a longer delay. Calculations suggest that the slower gas is more highly ionised and denser, with an estimated maximum distance of 0.05 parsecs from the source; the faster gas appears less ionised and less dense, with an estimated maximum distance of 0.25 parsecs. These estimates are approximate: a time-dependent model could not reproduce the strongest measured change, and uncertain starting conditions prevented a precise density measurement. The slower gas may be a failed wind, moving too slowly to escape, while the faster gas is near the escape threshold. Together with a detection from 2001, this supports a picture of failed winds containing gas in different ionisation states.
Young explorerScientists watched a galaxy called NGC 3783 for ten days. They saw gas blocking some X-ray light, and the amount it blocked changed. Slower and faster gas changed in different ways when the galaxy got brighter or dimmer. Their calculations suggest that some gas may be moving outward too slowly to escape. But the calculations did not explain every change, so the scientists are still unsure about parts of the story.
B. Longo, V. Bosch-Ramon, M. Perucho+1 more
AstronomerThis modeling study investigates non-thermal emission from supernova ejecta interacting with an extragalactic jet on kiloparsec scales. The authors post-process a three-dimensional relativistic hydrodynamics simulation with a simplified, computationally efficient model of electron acceleration, transport, synchrotron radiation, and inverse Compton emission. For intermediate jet powers, they predict potentially detectable radio, optical, and X-ray fluxes at distances below 100 Mpc. The modeled luminosity budget and local conditions could explain observed knots in kiloparsec-scale jets at multiple energies, but this is a proposed interpretation rather than an established identification. The conditions might also support heavy ultra-high-energy cosmic-ray production, while hadronic photon and neutrino emission would be minor on these scales. Predicted leptonic gamma-ray fluxes are modest, though they might contribute non-negligibly at TeV energies for the nearest or more powerful jet sources.
PublicAn exploding star could encounter a fast-moving jet as the jet passes through the inner parts of its galaxy. This study uses computer simulations to explore how the star's expanding debris might interact with such a jet and how energized electrons could produce light. The models suggest that, for jets of intermediate power, the resulting radio waves, visible light, and X-rays might be detectable from less than 100 million parsecs away. Such interactions could help explain bright patches already seen in galaxy jets, but the study does not establish that these patches were caused by supernovae. The modeled conditions might also accelerate heavy particles to extremely high energies. Gamma rays produced by electrons are predicted to be modest, although they could make a meaningful contribution at very high energies in nearby or more powerful jet sources; photons and neutrinos produced through interactions involving atomic nuclei would be minor on the scales studied.
Young explorerSometimes a star explodes near a huge, fast stream of material in a galaxy. Scientists used a computer to imagine what could happen if the exploding star's pieces ran into that stream. Their model suggests the crash could make bright spots that telescopes might see if the galaxy is close enough. This could explain some bright spots in galaxy streams, but the scientists have not shown that those spots really came from exploding stars.
E. Concepción, T. Petrushevska, G. Leloudas+21 more
AstronomerA real-time Lasair filter selected ZTF transients coincident with host-galaxy nuclei without photometric cuts, aiming to retain SMBH-related flares in both quiescent and active hosts. Over 16 months it returned 476 candidates; 202 received spectroscopic classifications, predominantly supernovae, with 10 confirmed TDEs (5% of the classified subset) and one Bowen fluorescence flare. Mean g-r colour and rise time distinguish TDEs from the supernova background. The filter recovered 10 of 25 TDEs classified within the same period and declination range, with most misses attributed to technical or observational rather than physical causes. The authors conclude that positional filtering plus basic photometric criteria can efficiently isolate TDEs and that high completeness is achievable, rather than demonstrated by the current recovery fraction. For predominantly photometric LSST samples, they emphasize selection bias alongside contamination and the need to retain flares in active hosts.
PublicA bright flare near a galaxy’s centre does not necessarily come from its supermassive black hole: an exploding star can appear there too. Researchers tested a real-time search that selected such flares without first restricting their brightness or colour. It found 476 candidates over 16 months. Of the 202 classified using spectra, most were exploding stars, while 10 were confirmed events in which a black hole tears apart a star. Colour and the time taken to brighten helped distinguish these events from stellar explosions. The search recovered 10 of 25 known, classified star-disruption events in the matching time and sky region; most misses were attributed to technical or observational limitations. The researchers argue that simple screening could handle future large surveys efficiently, but warn that selection rules can exclude unusual flares, especially in galaxies with already-active centres.
Young explorerSometimes the middle of a galaxy suddenly gets brighter. It might be a star exploding, or a giant black hole tearing a star apart. Scientists found lots of flashes and checked some carefully. Most checked flashes were exploding stars, but ten were stars torn apart by black holes. A flash’s colour and how quickly it brightens helped tell them apart. Their search still missed some, so they want searches that do not leave unusual flashes out.
Chengchao Yuan
AstronomerThe study couples stochastic acceleration to nuclear and radiative cascades to assess nuclear contributions to high-energy neutrino emission from Seyfert galaxies. In the model, acceleration and losses limit the energy per nucleon available to cascades; fragmentation cannot increase that scale without secondary reacceleration. For NGC 1068, joint neutrino and gamma-ray constraints permit larger nuclear power fractions for helium-dominated injection than for the heavier mixtures considered. For NGC 7469’s harder candidate neutrino spectrum, the adopted model produces more energetic nuclear cascades, and source-specific flux selections permit larger fractions for heavier mixtures than in NGC 1068. These are model-dependent composition constraints, not a determination of the accelerated composition, and depend on nuclear yields, acceleration conditions, and available power.
PublicResearchers modeled how atomic nuclei accelerated near supermassive black holes could contribute to high-energy neutrinos from Seyfert galaxies. Their calculations show that acceleration and energy losses limit the energy available per nuclear building block; breaking nuclei apart cannot raise that limit unless the fragments are accelerated again. For NGC 1068, neutrino and gamma-ray constraints allow a larger share of power in nuclei when the starting mixture is mostly helium rather than the heavier mixtures tested. For NGC 7469, a tentative neutrino spectrum extending more strongly toward high energies leads to more energetic cascades in the model. Its source-specific flux selections also allow larger shares for heavier mixtures than in NGC 1068. The actual nuclear mixture remains uncertain, and the limits depend on the model and available power.
Young explorerScientists used a model to explore how tiny pieces of atoms near huge black holes might help make particles called neutrinos. Different kinds of atoms gave different answers, and the answer changed between two galaxies. Breaking an atom’s center into smaller pieces did not give each piece more energy unless it got another boost. This is a model, not proof of which atoms are really there.
Noa Grollimund, Stéphane Corbel, Lauren Rhodes+14 more
AstronomerDense radio, NIR/optical/UV, and X-ray monitoring of the black hole low-mass X-ray binary Swift J1753.5-0127 traces its faint, hard-only, double-peaked 2023–2024 outburst and subsequent optical re-brightening. New and archival luminosities refine its radio/X-ray relation across the steep/outlier and shallow/transition branches, confirming hybrid behavior. Its location resembles that of MAXI J1348-630, but at lower radio luminosities than H 1743-322. Fits to four quasi-simultaneous broadband SEDs indicate that a cool, truncated accretion disk dominates the NIR/optical/UV emission. The compact jets contribute variably but weakly in the NIR, with a break frequency constrained to approximately 5 × 10^12 Hz or below, supporting the view that radio-quiet sources are also infrared-quiet. There is evidence that the radio spectral index changes from inverted near quiescence to flatter or negative at higher X-ray luminosities. Within adiabatic jet models, this trend may indicate increasing geometric confinement of the jet as the accretion rate rises; that explanation remains an interpretation rather than a direct measurement of jet geometry.
PublicAstronomers followed Swift J1753.5-0127, a black hole binary system, during its 2023–2024 outburst to study how incoming gas relates to outgoing jets. Observations spanning radio waves, infrared, visible and ultraviolet light, and X-rays revealed a faint outburst with two peaks, followed by another brightening in visible light. Combining these observations with earlier measurements confirmed that the system switches between two patterns linking its radio and X-ray brightness. Models fitted to the light across these wavelengths suggest that a cool gas disk, whose inner edge stops short of the black hole, supplies most of the infrared-to-ultraviolet emission. The jets make only a weak, changing contribution in the near-infrared. The radio spectrum also appears to change as the X-ray brightness increases. In one class of jet models, this could mean the jets become more tightly confined as more gas flows inward, but the observations do not directly establish that explanation.
Young explorerA black hole can have gas swirling around it and jets carrying some material away. Scientists watched one such system brighten twice, then brighten again in visible light. They think most of its infrared and visible light came from the swirling gas, while the jets added only a little infrared light. Changes in its radio waves might mean the jets were getting squeezed more tightly, but scientists are not sure.
Sloane Sirota, Duncan R. Lorimer
AstronomerCHIME/FRB Catalog 2 contains 3,641 bursts, including 981 from 83 repeating sources, with a reported observed repeater fraction of 2.3%. The authors use simulation-based inference to compare eight population models, four containing a truly one-off subpopulation. Within this model comparison, the catalog strongly favors a one-off component; the best-fitting model combines log-normal burst rates, Poissonian waiting times, and one-off sources. An independent random forest classifier supports this preference, and models containing one-off sources reproduce hyperactive repeaters not included in training, providing a consistency check. The authors place upper limits on the potentially observable population in the CHIME sky of 36,000 repeating sources and 19 one-off sources per day. They predict an observed repeater fraction below 2% within five years, eventually approaching approximately 0.5%. These are model-based constraints and predictions: the preference for a one-off subpopulation is not direct confirmation that individual apparently nonrepeating sources can never repeat.
PublicFast radio bursts are brief flashes of radio waves from space. CHIME's second catalog lists 3,641 bursts, including 981 flashes from 83 sources seen to repeat. But a source seen only once might flash again later. To investigate whether some sources truly flash just once, researchers compared eight simulated population models with the catalog. The data strongly favored models mixing repeating and genuinely one-time sources over the alternatives tested. A separate machine-learning analysis supported that preference, and the favored models also reproduced unusually active repeaters without training on them. This is evidence from modeling, not proof that any particular source will never repeat. The researchers predict that the observed percentage of repeaters will fall below 2% within five years and eventually approach 0.5%.
Young explorerScientists watch for quick radio flashes from space. Some places flash again and again, while others have been seen flashing only once. The scientists tried computer models to help explain this. Models with both repeating flashes and places that flash just once fit best. But seeing only one flash does not prove another will never come. The models predict that, as more flashes are found, a smaller share of the sources will be seen repeating.
Xinze Guo, Ryan Chornock, Raffaella Margutti+13 more
AstronomerTDE 2022dbl is a partial tidal disruption event candidate with two distinct UV/optical flares. Using 11 new optical spectra, updated UV/optical photometry, and a Keck-II/ESI host-galaxy spectrum, the authors find that the blended N III + He II feature evolves from N III-dominated to He II-dominated emission across both flares. This may indicate changing ionization conditions and declining Bowen-fluorescence efficiency. Similar thermal evolution and spectral features support, but do not establish, repeated partial disruption. The second flare has a broader, plateau-like peak, a longer decline timescale, and less extreme line velocities; the authors suggest interaction between second-disruption debris and an accretion disk formed during the first flare. Host-galaxy velocity dispersion implies log10(M_BH/M_sun) = 6.01 ± 0.45. No third flare was detected at the expected recurrence epoch. The authors propose that a positive-energy kick during ballistic core reformation delays the surviving remnant's return.
PublicTDE 2022dbl has produced two separate flares of ultraviolet and visible light. The observations support a scenario in which a star survived a close encounter with a supermassive black hole and lost more material on a later passage, although this explanation remains unconfirmed. The two flares showed similar temperature changes and spectral features, but the second had a broader, flatter peak, faded more slowly, and showed less extreme gas speeds. The researchers suggest that material stripped during the second encounter interacted with a disk formed during the first. Changes in the light emitted by nitrogen and helium may reflect changing ionization conditions and less efficient production of nitrogen emission through fluorescence. The host galaxy's stellar motions imply a black hole mass of roughly one million Suns, with substantial uncertainty. No third flare was detected when expected. The authors propose that an energy boost as the surviving stellar core re-formed delayed its return, rather than treating that delay mechanism as an established result.
Young explorerAstronomers saw two bright flashes from a place called TDE 2022dbl. They think a giant black hole may have pulled some material off a star twice, while the star survived. The flashes looked alike in some ways, but the second stayed bright longer and faded more slowly. One idea is that the newly pulled-off material bumped into material left from the first visit. Astronomers did not see a third flash when they expected one. They suggest the leftover star may have received a push that made its next trip take longer, but they do not know for sure.
Constantino Tsallis, Ugur Tirnakli
AstronomerThe authors analyze recent IceCube astrophysical-neutrino spectra and report satisfactory q-Gaussian descriptions across the full measured energy interval, analogous to descriptions of cosmic-ray and proton-proton LHC spectra. They infer a momentum-distribution nonadditive index q ≃ 1.6, compared with ≃ 1.2 for cosmic rays and ≃ 1.1 for LHC collisions. They interpret the larger index as indicating very-long-range space-time correlations and argue that the fits strengthen evidence for nonadditive entropy frameworks, including S_q, S_delta, or alternatives, in black-hole and cosmological phenomena such as dark energy. These broader connections are interpretations, not direct measurements of those phenomena; the underlying physical mechanisms remain unresolved.
PublicThe authors report that a mathematical curve called a q-Gaussian fits IceCube measurements of astrophysical neutrinos across the measured energy range. Similar curves describe cosmic-ray and particle-collision data, but the neutrino fit has a larger value of the curve’s q parameter: about 1.6, versus about 1.2 and 1.1, respectively. The authors interpret this difference as a sign of connections extending over very large distances and times. They also suggest it supports broader ideas about entropy relevant to black holes and dark energy, rather than directly demonstrating those connections. What physical processes could produce the pattern remains an open question.
Young explorerScientists looked at measurements of tiny particles from space called neutrinos. They found that a special math curve matches the pattern well. Similar curves match other particle measurements, but this one has a different shape. The scientists think this could be a clue that things happening very far apart in space and time are connected. They do not yet know what would make that happen.
Mattia Di Mauro
AstronomerThe authors investigate an inelastic-dark-matter interpretation of LZ’s reported 248 keV nuclear-recoil candidate, not a confirmed dark-matter detection. Their anomaly-free gauged-baryon-number model uses a vector mediator, Z_B, to couple dark matter to quarks. Symmetry breaking generates particle masses and a small splitting between two dark-matter states, with a residual symmetry stabilizing the lighter state. Within the scanned domain, model regions compatible with the candidate, the observed dark-matter abundance, and current ATLAS/CMS dijet constraints span correlated values of m_chi ≈ 0.19–4.5 TeV, M_Z_B ≈ 0.05–5.0 TeV, and g_B ≈ 0.004–0.74. A representative thermal solution has m_chi = 1 TeV, M_Z_B = 1.44 TeV, g_B ≈ 0.228, and a 300 keV splitting. Small electroweak mixing enables rapid decay of the heavier state, suppressing signals from its surviving population. Proposed complementary tests include further LZ/XENONnT recoil data, ATLAS/CMS Run-3 dijet searches, and a dedicated IceCube analysis of four-quark final states from solar dark-matter capture and annihilation. These would probe different parts of the surviving parameter region and assess the interpretation.
PublicLUX-ZEPLIN reported a possible collision event that motivates a dark-matter explanation, but the event does not establish that dark matter was detected. The researchers explore a model in which a dark-matter particle hits an atomic nucleus and changes into a slightly heavier particle. A proposed new force-carrying particle connects dark matter to quarks. Their calculations identify combinations of particle masses and interaction strengths consistent with the event, the observed amount of dark matter, and existing collider limits. In the model, the heavier dark-matter state decays quickly, reducing otherwise unwanted signals. The authors propose several ways to check the explanation: more underground-detector data, collider searches, and an IceCube study of possible dark-matter capture and annihilation in the Sun. These tests would examine different aspects of the model rather than guarantee confirmation.
Young explorerA detector saw a tiny bump that might have come from dark matter, but scientists do not know yet. They explored an idea: an unseen particle could bump into an atom’s center and become a little heavier. The idea fits some checks so far. More detector clues could help scientists find out whether it is right.
Leif Lui, Adrian Ka-Wai Chung
AstronomerThe authors numerically compute leading-order quasinormal-mode frequency shifts for rapidly rotating black holes surrounded by massive scalar fields with nonminimal curvature coupling. For reduced Compton wavelengths no shorter than the black-hole mass scale and dimensionless spins from 0 to 0.9, numerical errors in the shifts are typically 10^-8–10^-5, rising to at most order 10^-3 near the scalar-mass threshold. These calculations suggest a possible route to searching existing gravitational-wave signals for ultralight scalar particles, which are dark-matter candidates; no particle detection or analysis of observed signals is reported.
PublicBlack holes have characteristic ringing frequencies. This study calculates how those frequencies would shift if a spinning black hole were surrounded by a particular kind of massive scalar field coupled to spacetime curvature. The calculations have small numerical errors over the stated range of field wavelengths and black-hole spins, though errors are larger near a scalar-mass threshold. The results could help researchers search existing gravitational-wave signals for ultralight particles that might make up dark matter. This is a theoretical calculation, not evidence that those particles have been found.
Young explorerA black hole can ring a little like a bell. Scientists used a computer to work out how its ring might change if a special kind of invisible stuff were around it. That could help them look for tiny particles that might be dark matter, but they have not found those particles in this study.
Giorgio Galanti
AstronomerThe authors present bound, sub-parsec binary blazars as a proposed class of broadband, beam-beam hadronic cosmic colliders. In this scenario, co-streaming proton beams with jet misalignments of about 1–6 degrees reach center-of-mass energies near 10^10 GeV, roughly six orders of magnitude above the Large Hadron Collider. With proton–proton optical depth much less than unity, collisions remain rare, but the system samples a continuous range of center-of-mass energies. The authors argue that this could probe asymptotic QCD scaling, gluon saturation, and Froissart unitarity, with a possible high-sensitivity window on physics beyond the Standard Model. Predicted secondary PeV–EeV neutrinos and sub-TeV gamma rays are described as within reach of current and planned facilities including LHAASO, CTAO, IceCube, and GRAND. The abstract presents a physical scenario and its proposed observational prospects, not a reported detection of these collisions or new physics.
PublicThe study proposes that two closely bound blazars could act as a natural particle collider. Their jets contain beams of protons moving in nearly the same direction; a small difference in their directions could allow collisions at energies roughly a million times above those of the Large Hadron Collider. Most protons would pass through without colliding, but the collisions that do occur could span a wide range of energies. The authors predict that these interactions would produce neutrinos and gamma rays potentially accessible to current and planned observatories. Such signals might test how the strong nuclear force behaves at extreme energies and possibly reveal physics beyond existing theory. These are proposed capabilities and predicted signals, not confirmed observations.
Young explorerScientists have an idea about two jets of tiny particles close together in space. If the jets point in slightly different directions, some particles could bump into each other with much more energy than in machines on Earth. Most particles would pass by without a bump. The bumps could send out light and tiny particles that special detectors might find. Scientists have not reported finding those bumps here; they are explaining what could happen.
Sumanta Chakraborty, Takuya Katagiri, Paolo Pani+1 more
AstronomerThis analytical study determines the static tidal response of Kerr–Newman black holes in four-dimensional Einstein–Maxwell theory, using a recent advance in separating their coupled gravitational and electromagnetic perturbations. For arbitrary multipole order, charge, and spin, the full matrix of conservative tidal Love numbers vanishes, including mixed gravito-electromagnetic terms. The authors also calculate a nonvanishing static dissipative response induced by frame dragging. These are theoretical results, not observational measurements; vanishing conservative Love numbers does not imply that every component of the tidal response vanishes.
PublicThe researchers calculated how a black hole with both rotation and electric charge responds to steady external gravitational and electromagnetic disturbances. Their analytical result is that all its conservative tidal Love numbers—quantities describing the response without dissipation—are zero, including those linking gravitational and electromagnetic effects. However, they also find a nonzero dissipative response caused by frame dragging, the effect associated with the black hole’s rotation. This is a theoretical calculation, not an observation, and it does not mean the black hole has no response at all.
Young explorerScientists used math to ask how a spinning black hole with electric charge reacts when its surroundings gently tug on it. They found that one kind of steady response is zero. But spinning can cause another kind of response, where energy is lost. They worked this out with math, rather than by watching a real black hole.
J. P. Carlomagno, G. A. Contrera, A. G. Grunfeld+1 more
AstronomerThis theoretical study tests equation-of-state-insensitive relations for quark cores in hybrid stars and whether global observables constrain core size. Three-flavor MIT bag quark matter with repulsive vector interactions is matched to DD2 hadronic matter through a Maxwell construction. Scanning the bag-constant and vector-coupling plane yields 1112 hybrid EOSs with maximum masses above two solar masses, broadly compatible with current multimessenger constraints. Across stable configurations, global properties follow hadronic-star relations, with the I–Love relation accurate to within 0.5%, whereas core properties follow self-bound strange-star relations with median deviations of 6–9%. A first-order compactness expansion attributes the core relations to compactness and interface properties, chiefly ξ, the transition pressure divided by the quark-side energy density. The strange-star relations correspond to the ξ → 0 limit, and deviations encode ξ. Fractional core masses and radii follow the normalized stellar mass profile, but no global observable determines core size within the modeled configurations. Vanishingly small cores dominate the viable parameter space; sizable cores require low bag constants and strong vector couplings.
PublicCan a compact star’s outward properties reveal a quark-matter core? This study explores that question with theoretical models, not a new observation. The researchers constructed 1112 descriptions of matter that allow hybrid stars with maximum masses greater than twice the Sun’s mass and are broadly compatible with current observational constraints. The modeled stars’ overall properties obey relationships much like those of ordinary neutron stars. Their quark cores instead approximately obey relationships associated with stars made entirely of self-bound strange matter, with typical deviations of 6–9%. The researchers explain these differences through conditions at the boundary between the core and the surrounding matter. However, within these models, no overall observable reveals the core’s size. Very small cores dominate the viable model choices, while large cores require particular combinations of the quark-matter model’s parameters.
Young explorerScientists used math to study stars that might have a special middle made of quark matter. They did not find a new star with one of these middles. In their models, the whole star followed one set of patterns, while its middle roughly followed another. Most allowed choices gave very tiny middles. The star’s overall properties did not tell them how big its middle was.
Bikram Keshari Pradhan, Jérôme Margueron, Guy Chanfray+1 more
AstronomerThis theoretical study tests a direct mapping from internal nucleon properties to the equation of state of ultra-dense quark matter using π+ω and π+ω+ρ soliton models. In the model including the ρ field, the pressure derived from the canonical energy-momentum tensor has a central singularity that affects the mapped equation of state; pressure obtained after a Belinfante pseudo-gauge transformation is nonsingular. However, none of the tested nucleon-pressure prescriptions yields an equation of state consistent with the thermodynamic pressure defined for uniform matter. These model results call into question the simple direct mapping from finite-size nucleons to uniform matter and raise questions about the nucleon surface's role in internal energy density and pressure; they are not observational findings.
PublicThe researchers use theoretical models to ask whether the pressure inside protons and neutrons can tell us how extremely dense matter behaves. They compare two models and find that one way of calculating pressure produces a singularity at the particle's center, while another mathematical formulation avoids it. Yet none of the pressure recipes they test agrees with the thermodynamic pressure for uniform matter. This suggests that directly translating the properties of individual, finite-sized particles into those of uniform dense matter is too simple in these models. The work also raises questions about how a particle's surface contributes to its internal energy density and pressure. These are theoretical results, not measurements of real dense matter.
Young explorerScientists used math models to study tiny particles called protons and neutrons. They asked whether the push inside one tiny particle could tell them about the push in very tightly packed matter. One math recipe made the push go wrong at the particle's middle, and another avoided that problem. But none of the recipes they tried matched the pressure calculation for matter spread evenly throughout. So copying the inside of one tiny particle may not be enough to describe all that packed matter. This was a math study, not something they watched happen.
Shuochong Han, Xiangdong Sun, Zhenyu Zhu+1 more
AstronomerThis theoretical study extends the quark mean-field (QMF) model to finite temperature and compares uniform nuclear matter with relativistic mean-field (RMF) predictions. Each model uses two parameter sets calibrated to the same selected saturation properties but with different nucleon Dirac effective-mass ratios at saturation. Calculations cover effective masses, beta-equilibrium composition, and thermodynamic properties of symmetric nuclear matter, pure neutron matter, and beta-equilibrium matter. The models show similar qualitative trends but increasingly divergent predictions at high density, associated with distinct effective-mass density dependences and especially apparent in thermal pressure and the thermal index. For the two parameter sets studied, compact thermal-index fits span baryon densities of 0.08–1.0 fm^-3, temperatures of 5–100 MeV, and isospin asymmetries of 0–1, reproducing numerical results to better than 2% accuracy. These fits are ready for implementation in binary neutron-star merger simulations; effects on thermal support and post-merger dynamics remain subjects for future assessment, not demonstrated merger results.
PublicThe researchers developed a finite-temperature version of a model that describes nuclear matter using quark structure, then compared its calculations with those of another model. Both predict broadly similar behavior, but their predictions differ more strongly at high density, particularly in how heating contributes to pressure. The team also produced compact formulas for the thermal index, a quantity used to describe thermal pressure. Within the tested conditions and parameter choices, these formulas match the detailed numerical calculations to better than 2%. They could be used in simulations of merging neutron stars, but this study does not establish how the model changes the aftermath of a merger. Its findings are theoretical predictions, not observations.
Young explorerScientists made a math model for very hot, tightly squeezed matter and compared it with another model. The two models give more different answers when the matter is packed very tightly, especially about how heat helps it push outward. The scientists also made shorter math rules that closely match their longer calculations. These rules could help people make computer models of two neutron stars joining together. They have not yet shown what the new rules will change in those star models.
Zhiqiang Miao, Junquan Su, Neev Khera+1 more
AstronomerThe authors present what they describe as the first causal relativistic theory to place direct, quasinormal-mode, and late-time-tail tidal responses on equal footing for a nonrotating perfect-fluid star. A spectral decomposition of the retarded Green function for a matched stellar interior and Schwarzschild exterior identifies four time-domain regimes: acausal region, prompt wave, surface-reflected wave, and mode plus tail. The prompt signal matches that of a Schwarzschild black hole of the same mass; together with the surface-reflected wave, it forms the direct response. A complex bilinear form on the full metric–fluid phase space yields discrete projections for evolving quasinormal-mode amplitudes and continuum branch-cut projections for direct and tail amplitudes, with explicit first-order driven evolution equations for every sector. The resulting complete modal–nonmodal decomposition is verified numerically under generic time-dependent tidal driving, rather than through astronomical observations. Applications to black hole perturbations are discussed.
PublicThis theoretical study describes how a star responds to a changing tidal pull when Einstein’s general relativity must be used. The response includes an early wave, a wave reflected from the star’s surface, characteristic oscillations, and a lingering tail. The authors find that the earliest signal is identical to that of a black hole with the same mass, although the full stellar response includes additional components. Their framework tracks both the star’s fluid and the disturbances in spacetime, combining characteristic oscillations with components that cannot be represented by those oscillations alone. They test the framework numerically for changing tidal forces; these are mathematical and computational results, not observations of stars. The theory assumes a nonrotating star described as a perfect fluid, and possible uses for studying black hole disturbances are discussed.
Young explorerWhen gravity gives a star a changing tug, the star and the space around it can wobble. The scientists made a math recipe to follow the first waves, waves that bounce off the star’s surface, and wobbling that lingers afterward. Their recipe is for a star that is not spinning and whose material behaves like an ideal fluid. They checked it with computer calculations, not by watching a real star.
Valery F. Suleimanov, Victor Doroshenko, Klaus Werner
AstronomerThe study combines cataclysmic variables (CVs) detected in the Swift/BAT all-sky hard X-ray survey with reliable Gaia distance estimates. For this sample, it derives a local number density per solar mass of 1.37 (+0.30/−0.16) × 10^-5 M_sun^-1 and a luminosity density per solar mass of 8.95 (+0.15/−0.10) × 10^26 erg s^-1 M_sun^-1. These estimates appear consistent with the integrated Galactic ridge X-ray emission and Nuclear Stellar Cluster luminosities, supporting—but not establishing—the proposed CV origin of this extended emission. Differential number- and luminosity-density functions distinguish two populations: intermediate polars dominate above L_X = 10^33 erg s^-1, while non-magnetic CVs and polars are much more numerous but fainter on average. The two populations consequently contribute nearly equally to the observed hard X-ray luminosity.
PublicCataclysmic variables are the most numerous hard X-ray sources in our Galaxy, and they are thought likely to account for the extended hard X-ray glow along the Galactic ridge and near the center. Researchers studied objects found by the Swift/BAT survey that also have reliable distances from Gaia, estimating how common they are locally and how much X-ray light they produce per unit mass. The estimates appear to agree with the measured Galactic ridge emission and the luminosity of the central Nuclear Stellar Cluster, supporting that explanation without proving it. The sample separates into two groups: brighter intermediate polars and a much more numerous, typically fainter group of non-magnetic cataclysmic variables and polars. Despite their different numbers and brightnesses, the two groups provide almost equal amounts of hard X-ray light.
Young explorerScientists studied objects in our galaxy that shine in a kind of light called X-rays. One group has brighter objects. The other group has many more objects, but they are usually dimmer. Adding up their light, the two groups give almost the same amount. The scientists think these objects may explain a big X-ray glow in parts of our galaxy, and their study supports that idea, but does not prove it.
Muhammed Saleem, Hsin-Yu Chen, Daniel M. Siegel+3 more
AstronomerThe study tests whether neutron star–black hole mergers or fast-merging binary neutron stars can provide the additional r-process enrichment suggested by Milky Way disk abundances. A unified likelihood-based framework combines LIGO-Virgo-KAGRA gravitational-wave observations, short gamma-ray bursts, Galactic pulsars, and Galactic Eu/Fe versus Fe/H measurements, propagating uncertainties in merger rates, delay-time distributions, mass- and spin-dependent ejecta yields, and stellar abundances. The analysis finds that neither candidate can dominate the additional enrichment without strong tension with existing observations and theoretical expectations. This constrains their proposed roles rather than excluding their contributions, and supports the need for non-merger production channels.
PublicMergers of two neutron stars are an established source of elements made by rapid neutron capture, known as the r-process. But evidence from stars in the Milky Way suggests that another source is needed. Researchers combined gravitational-wave observations with information from short gamma-ray bursts, pulsars, and stellar chemical abundances to test two possibilities: mergers between neutron stars and black holes, and neutron-star pairs that merge quickly. Their analysis accounts for uncertainties in how often mergers occur, how long they take, and how much material they eject. Neither possibility could supply most of the additional enrichment without strongly conflicting with observations and theoretical expectations. The findings support the need for sources other than mergers, but do not identify those sources.
Young explorerWhen two neutron stars crash together, they can make some heavy elements. But clues from stars in our galaxy suggest these crashes do not explain all of those elements. Scientists checked whether crashes with black holes, or neutron-star pairs that crash quickly, could make most of what is missing. After allowing for things they are unsure about, they found that neither idea fits the clues well enough to do that. Their work suggests another kind of event is needed, but it does not tell us which one.
Samsuzzaman Afroz, Suvodip Mukherjee
AstronomerThe authors apply a non-parametric Bayesian framework to the LIGO-Virgo-KAGRA GWTC-3 and GWTC-4 catalogs to investigate redshift evolution of the binary black hole mass distribution. Accounting for detector selection effects, the method jointly tests linear and quadratic evolution relative to the low-redshift population. They find tentative evidence for linear evolution at masses roughly above 50 solar masses, but no significant evolution for lower-mass systems. The quadratic term is consistent with zero, suggesting that a linear dependence adequately describes the population up to z ≈ 1. These findings do not establish a particular formation channel; larger future gravitational-wave samples could reveal subtler evolutionary features and help constrain black hole formation history.
PublicResearchers used gravitational-wave catalogs to ask whether the masses of black holes in pairs change across cosmic history. Their statistical method accounts for the fact that detectors are more likely to detect some systems than others. They found tentative signs of a change with redshift—a marker of cosmic time—for masses roughly above 50 times the Sun’s mass, but no significant change for lower-mass systems. A simple straight-line trend appears sufficient over the range studied, up to a redshift of about 1; the analysis found no significant additional curvature. More detections could clarify these hints and help researchers understand how black holes formed throughout the universe’s history.
Young explorerScientists studied tiny ripples in space made by pairs of black holes. They asked whether black holes in pairs were different sizes long ago. They found a small hint that the very heavy ones changed over time, but they are not sure yet. They did not find a clear change for the lighter ones. Finding more of these ripples could help them learn how black holes came to be.
David Wittman, Rodrigo Stancioli, Faik Bouhrik+2 more
AstronomerRXC J0032.1+1808, previously found to be elongated north–south in optical imaging and gravitational-lensing mass maps, has a bimodal X-ray morphology suggestive of an ongoing merger. Together with a previously reported radio relic, this supports the authors’ interpretation that the system is observed after first pericenter. Archival XMM-Newton data yield a global X-ray temperature of 8.5 keV (+1.1/−0.9) and an unabsorbed 0.5–10.0 keV luminosity of (1.04 ± 0.03) × 10^45 erg/s, with uncertainties at 90% confidence. A member-galaxy redshift survey gives a relative line-of-sight velocity of 1002–1785 km/s between the subclusters at 68% confidence; the brightest cluster galaxies differ by 2466 km/s. Comparison with publicly available hydrodynamic simulations rules out a head-on merger within the models considered and is consistent with impact parameters of 0.5 or 1 Mpc. The simulation comparison provides initial, model-dependent constraints of approximately 315–550 Myr since pericenter and a locus of possible viewing directions.
PublicThe galaxy cluster RXC J0032.1+1808 appears to be two smaller clusters merging. Earlier images and maps of its mass showed a north–south stretch; the new X-ray analysis reveals two main concentrations of hot gas. These observations, together with a previously detected radio feature called a relic, lead the researchers to suggest that the clusters have already made their first closest pass. X-ray data measure the gas temperature and luminosity, while galaxy redshifts indicate that the two groups differ in their motion along our line of sight by 1002–1785 km/s, at 68% confidence. Comparisons with computer simulations favor an off-center encounter rather than a head-on collision. Those simulations provide preliminary estimates that the closest pass occurred roughly 315–550 million years ago, and constrain the directions from which we could be viewing the merger; these are model-based inferences, not directly measured dates or geometry.
Young explorerTwo enormous groups of galaxies seem to be coming together. Scientists see two big patches of hot gas, which help them spot the two groups. They think the groups have already passed close to each other once. By comparing what they see with computer models, they think the groups passed a little to the side, rather than meeting straight on. The models suggest that their closest pass happened hundreds of millions of years ago, but scientists are still working out exactly how it happened.
Simon Chiche, Simona Toscano, Krijn D. de Vries
AstronomerUsing the FAERIE Monte Carlo framework, the authors report the first characterization of cosmic-ray radio signals in simulations incorporating both in-air and in-ice emission. They investigate radiation energy, timing, polarization, and frequency spectra, quantifying their dependence on shower properties. Cosmic-ray-induced showers are a primary background for ultra-high-energy neutrino searches with deep in-ice radio antennas, but can also validate the detection principle and provide calibration signals. The simulation results offer guidelines for cosmic-ray identification and cosmic-ray/neutrino discrimination in future in-ice radio experiments; the abstract does not report observational validation or discrimination performance.
PublicExperiments searching for extremely energetic neutrinos use antennas deep in ice to look for radio signals produced by particle cascades. Cosmic rays also produce particle showers and radio signals, creating a major background for these searches while potentially providing useful calibration signals. In this study, researchers used computer simulations that include cosmic-ray radio emission both in the air and in the ice. They examined how the signals’ energy, timing, polarization, and frequency content depend on the particle showers. The simulated results provide guidance for identifying cosmic rays and distinguishing them from neutrinos in future experiments, rather than demonstrating that separation in observations.
Young explorerScientists put antennas deep in ice to listen for radio signals from tiny particles called neutrinos. Other particles, called cosmic rays, can make signals too, so telling them apart is tricky. The scientists used a computer to pretend cosmic rays were making signals in the air and in the ice. They studied what those signals would be like. This could help scientists tell the two kinds apart in future experiments, but this study used computer-made signals, not signals measured in the ice.
Simon Chiche, Olivier Martineau-Huynh, Matias Tueros+1 more
AstronomerThe authors present an updated Radio Morphing, a semi-analytical tool that estimates radio emission from cosmic-ray-induced air showers with zenith angles greater than 60 degrees at arbitrary antenna positions, using a few reference shower simulations. Updates include refined zenith-angle scaling laws, a new interpolation method, charge-excess emission, and optional shower-to-shower fluctuations. Tuned for a GRAND-like detector, the tool is reported to run four orders of magnitude faster than standard Monte Carlo simulations, with peak-amplitude accuracy better than 17% for unfiltered traces, better than 13% in the 50–200 MHz band, and below approximately 10% in the 30–80 MHz band. These are simulation-tool performance results, intended to support detector design studies and air-shower reconstruction development, rather than observational findings.
PublicPlanning large radio experiments requires many computer simulations of the radio signals produced when cosmic rays trigger cascades of particles in the atmosphere. Detailed simulations are reliable but too slow to explore all possible detector designs. The researchers present an updated shortcut called Radio Morphing, which uses a few reference simulations to estimate signals at other antenna locations for showers arriving at angles more than 60 degrees from vertical. In performance tests tuned for a detector like GRAND, the tool is reported to be about 10,000 times faster than standard simulations. Its peak-signal accuracy is better than 17% without frequency filtering, better than 13% over 50–200 MHz, and below about 10% over 30–80 MHz. These results concern computer modeling, not newly observed cosmic-ray signals.
Young explorerWhen a tiny particle from space hits the air, it can start a shower of particles that makes radio signals. Scientists use computers to work out what radio antennas might hear. This study improves a computer shortcut that uses a few detailed examples to estimate other signals from showers coming in at a large slant. In the tests described, it worked about 10,000 times faster than the detailed method, though its answers were not exact. It could help scientists plan big groups of radio antennas. The study tested a computer tool, rather than reporting new signals from the sky.
Hui-Ming Zhang, Su-Jie Lin, Jie Feng+4 more
AstronomerThe authors develop a unified, charge-dependent solar modulation model by solving the three-dimensional Parker transport equation with a realistic wavy heliospheric current sheet for self-consistent drift effects. They adopt a GALPROP local interstellar spectrum constrained by Voyager data and fit time-resolved AMS-02 proton and antiproton fluxes from May 2011 to June 2022, excluding the HMF polarity-reversal interval from mid-2012 to early 2015. Neural-network surrogate models accelerate computation of propagation and modulation matrices for parameter scans. The authors report that the model simultaneously describes both measured fluxes with physically reasonable parameters, supporting a unified treatment of charge-dependent modulation over the fitted intervals. The excluded reversal epoch is not covered by this reported fit.
PublicThe Sun’s magnetic environment changes the flow of incoming particles in ways that depend on their electric charge. Researchers built a model to describe these changes for positively charged protons and negatively charged antiprotons, including the effects of a wavy boundary in the Sun’s magnetic environment. They fitted the model to measurements from the Alpha Magnetic Spectrometer-02 taken between May 2011 and June 2022, using Voyager data to help constrain the incoming particle spectrum. Neural-network shortcuts made testing model parameters faster. The authors report that one model describes both particle types with physically reasonable settings. However, they excluded mid-2012 to early 2015, when the Sun’s magnetic field was reversing polarity, so the reported fit does not establish performance during that interval.
Young explorerTiny particles travel through space, and the Sun’s magnetism changes how they move. Scientists made a computer model for two kinds of particles with opposite electric charges. They say the same model fits measurements of both kinds. But they left out a time when the Sun’s magnetism was flipping, so this test does not tell us how well the model works then.
Hao Huang, Akira Dohi, Amira Aoyama+2 more
AstronomerMAXI and NinjaSat observed rapid cooling of the neutron star in MAXI J1752−457 over four days following an X-ray superburst. The authors propose enhanced neutrino emission from nuclear Urca cycles—electron capture and beta-minus decay involving odd-mass-number nuclei in the ocean—as the explanation, presenting this as a first indication of the process’s possible existence rather than a confirmed detection. They infer an ignition layer reaching approximately 4 GK near an ocean Urca shell, where Urca cooling could dominate for up to approximately two days after the superburst. This differs from normal Type-I bursts, whose hydrogen or helium burning occurs at much shallower depths. The work suggests that monitoring crust cooling on day-long timescales could probe superburst ashes through their Urca pairs.
PublicTwo Japanese satellites, MAXI and NinjaSat, observed a neutron star in MAXI J1752−457 cooling rapidly over four days after a powerful X-ray superburst. The researchers suggest that repeated nuclear transformations in the star’s ocean released neutrinos, particles that carried away heat. They describe this as the first indication that this proposed nuclear cooling process may occur, not a confirmed detection. Their interpretation implies a burst ignition layer reaching about four billion degrees, close to the region where these transformations could dominate cooling for roughly two days. Unlike ordinary X-ray bursts fueled by hydrogen or helium in shallower layers, superbursts ignite deeper. Tracking the subsequent cooling could help reveal the nuclear material left behind by a superburst.
Young explorerTwo satellites watched a very dense star cool quickly for four days after a big burst of X-rays. Scientists think tiny particles called neutrinos might have carried heat away as bits of matter inside the star changed back and forth. This is a possible explanation, not something they know for sure yet. Watching how the star cools could help them learn what the burst left behind.
M. A. Hashad, A. Hammad, Amr A. EL-Zant
AstronomerThe authors reanalyze five blazars with previously reported high-significance, year-scale quasiperiodic oscillations (QPOs), plus the nascent QPO candidate PKS 0139-09, using Fermi-LAT data through early 2025. Lomb–Scargle periodograms and Weighted Wavelet Z-transforms are applied after STL decomposition removes longer-term trends and often identifies a large seasonal component. Detrending generally strengthens the QPO signal, but all sources except PG 1553+113, which shows a clearly persistent QPO, exhibit transience on timescales of roughly 4000 days or less. Four-year light-curve forecasts use both a traditional statistical method and a Transformer model; the latter successfully predicts some test-set behavior not obvious from visual inspection of earlier data. Analysis of the forecast-extended series suggests weaker future QPO signals where transience occurs near the observational endpoint, but significant strengthening in PKS 0139-09. These are testable predictions, not observed future behavior, and their possible connection to the physical origin of QPOs remains uncertain.
PublicSome blazars show brightness changes that repeat approximately rather than like a perfect clock. Such patterns could offer clues about how their light is produced or possibly indicate pairs of supermassive black holes, but they do not establish either explanation. Researchers studied observations through early 2025 of five blazars with previously reported strong, roughly yearly patterns, plus another possible case, PKS 0139-09. Removing longer-term brightness trends generally made the repeating signals clearer. Only PG 1553+113 showed a clearly persistent pattern; the others showed patterns that were temporary on timescales of about 4000 days or less. The team then forecast four more years using statistical and artificial-intelligence methods. Those forecasts suggest that some patterns will weaken while the possible pattern in PKS 0139-09 will strengthen. Future observations are needed to check these predictions.
Young explorerScientists watched space objects called blazars get brighter and dimmer. Some seemed to follow a beat, but not a perfectly steady one. Taking away slow changes in brightness helped the scientists see the beats more clearly. Most of the beats did not last, but one blazar kept a clear beat. The scientists also used computer tools to guess what might happen over the next four years. They think some beats may get weaker and one possible new beat may get stronger. They will need to keep watching to see whether those guesses are right.
Raniere de Menezes
AstronomerA significant fraction of globular-cluster millisecond pulsars are isolated, although the accepted recycling scenario forms them in compact binaries. For non-core-collapsed clusters, the authors propose a framework combining the Heggie–Hills hard/soft binary law with companion ablation to trace the isolated fraction, F_i. They find F_i = (42.49 ± 1.62) a_H^(-0.5) %, where a_H is the Heggie–Hills ionization radius. The ionization-driven model is favored over an a_H-independent null hypothesis, with ln(BF) > 2.5. The framework also accounts for the observed overabundance of isolated MSPs in NGC 5139 (ω Centauri). These findings support a physical dependence on a_H and motivate binary ionization as a major formation mechanism in non-core-collapsed clusters, but do not establish the history of individual isolated pulsars.
PublicMany rapidly spinning pulsars in dense groups of stars called globular clusters have no companion, even though the standard explanation for their rapid rotation involves a close stellar partner. This study proposes that breaking apart stellar pairs, together with wearing away companions, can help explain the isolated population in clusters whose cores have not collapsed. The authors find that the fraction of isolated pulsars follows a relationship with a quantity describing binary disruption, and their model is statistically favored over one with no such relationship. It also accounts for the unusually large isolated population in Omega Centauri. The results support this explanation, but do not prove how each pulsar lost its partner.
Young explorerSome tiny stars spin very fast. Scientists think a partner star helped them spin up, but many are now alone. This study suggests that star pairs can split up, or a partner can get worn away. The idea helps explain the lonely spinning stars in some big groups of stars, but scientists do not yet know exactly what happened to each one.
Th. V. Papavasileiou, T. S. Kosmas, O. Kosmas+1 more
AstronomerBroadband modeling of soft-state NICER/NuSTAR spectra of MAXI J1820+070 favors Comptonized emission from a thin relativistic accretion disk plus two blackbody components with kT_bb = 0.5 and 0.2 keV. The inferred black-hole spin is a > 0.8, potentially contributing to the powering of its relativistic jets. Midway through the soft state, the analysis finds a significant decline in inner disk temperature and a modest increase in inferred inner disk radius to 3Rg. This is consistent with slight disk truncation recently predicted by GRMHD simulations, rather than a direct confirmation of that prediction. Spin-dependent radial temperature profiles and the relatively cool blackbody components suggest large emitting regions. The authors argue against a plunging-region origin for the soft X-ray excess and propose warm coronal layers farther from the black hole, analogous to warm Comptonization models for active galactic nuclei; this origin remains an interpretation.
PublicResearchers modeled X-ray observations of MAXI J1820+070 during its soft state to investigate how fast its black hole spins and where some extra low-energy X-rays come from. Their results indicate rapid spin, which could help power the system's relativistic jets. The analysis also finds that the inner part of the surrounding disk cooled substantially midway through this state, while its estimated inner edge moved slightly outward. That behavior fits a small retreat of the disk predicted by computer simulations, but does not prove the prediction. Two cooler emission components suggest that the extra X-rays may come from warm layers farther out above the disk, rather than the region where matter plunges into the black hole. This explanation is proposed, not established.
Young explorerA black hole has a disk of hot stuff around it. Scientists studied X-rays from one called MAXI J1820+070. Their model suggests that the black hole spins very fast. It also suggests that the inside of the disk got cooler and its edge moved a little farther away. Some extra X-rays might come from warm layers farther out, instead of stuff falling right into the black hole. Scientists still need to check that idea.
Ryotaro Chiba, Semih Tuna, Brian D. Metzger+1 more
AstronomerAround 10% of hydrogen-poor supernovae explode within compact, massive circumstellar material, indicating enhanced pre-explosion mass loss whose origin remains uncertain. The authors model the viscous evolution of a circumbinary disc supplied by time-dependent mass injection, motivated by binary-evolution calculations in which late-stage helium-star expansion triggers rapid but stable mass transfer. In these models, a lower accretion eigenvalue χ reduces fallback onto the binary despite initially sub-Keplerian injection. Their fiducial models yield pre-explosion disc masses of 0.07–0.20 solar masses, half-mass radii of 640–4000 solar radii, and an aspect ratio H/R of approximately 0.1. They further find that ejecta–disc interaction can power some rapidly evolving interacting Type Ibc supernovae classified as Fast Blue Optical Transients, such as SN 2018gep or SN 2019jc. These are model results, not direct measurements of the discs; uncertain model parameters remain, but the calculations support rapid, stable mass transfer as a viable origin for the observed dense environments.
PublicAbout one in ten hydrogen-poor supernovae explodes inside a compact, heavy concentration of surrounding gas. How the star shed that gas shortly before exploding is still unclear. This study explores a possible explanation involving two stars: as a helium star expands late in its life, it can rapidly transfer material to its companion, feeding a dense disc around the pair. The researchers calculated how such a disc would evolve and found that their models could retain enough material close to the stars to help explain the observed surroundings. Their calculations also indicate that an explosion striking the disc could power some exceptionally fast, bright events known as Fast Blue Optical Transients. The results support this explanation as a possibility, rather than proving it, because important model settings remain uncertain.
Young explorerSome exploding stars have lots of gas very close around them. Scientists are not sure how that gas got there. They used calculations to test an idea: a star with a nearby partner might share its gas and make a disc around both stars. If the star then explodes, the explosion could crash into the gas and make a bright flash that changes quickly. Their models show that this idea could work, but they have not proved that it is what really happened.
Longhua Qin, Jiancheng Wang, Chuyuan Yang+9 more
AstronomerThe study jointly analyzes five sets of simultaneous Fermi-LAT and LHAASO observations of the TeV blazar Mrk 421 to constrain axion-like particles (ALPs). Photon–ALP oscillations and extragalactic background light absorption are calculated together for two representative emission scenarios: a two-zone hybrid model and a single-zone hadronic model. A chi-squared profile analysis uses a Gaussian copula with rho = 0.03 to account for weak inter-epoch correlations; nuisance parameters are optimized under the no-ALP hypothesis before profiling ALP mass and photon coupling. For masses below approximately 1 neV, the reported 95% confidence upper limit is g_aγ = 6.35 × 10^-13 GeV^-1. Across 0.1–500 neV, the most conservative 95% confidence upper limits are 6.69 × 10^-12 GeV^-1 for the two-zone model and 7.37 × 10^-12 GeV^-1 for the single-zone model. These are model-dependent constraints, not an ALP detection. Changes to the background-light template, Galactic and intergalactic magnetic-field models, spectral binning, and residual instrumental systematics alter the limits by only a few percent. The jet magnetic field dominates the systematic uncertainty: it can move the low-mass bound by a factor of a few, and a substantially weaker single-zone field weakens the constraint by about an order of magnitude. The authors present the framework as a statistically consistent approach for future searches.
PublicResearchers combined five sets of gamma-ray observations of the blazar Mrk 421 from Fermi-LAT and LHAASO to test for hypothetical axion-like particles. Their calculations describe how gamma-ray photons might turn into these particles and back, while also accounting for light absorbed along the way. Rather than reporting a discovery, the study places 95% confidence upper limits on how strongly these particles could interact with photons. The limits depend on the assumed particle mass and on two different models of the blazar’s emitting jet. Most tested changes to the analysis affect the limits by only a few percent, but the jet’s magnetic field is a major uncertainty: changing it can weaken the low-mass limit by several times, or by roughly ten times for a substantially weaker field in the single-zone model. The authors also offer their analysis method as a tool for future searches.
Young explorerScientists studied very energetic light from a faraway object called Mrk 421. They were looking for clues about tiny particles that might exist. Their idea is that light could change into these particles and then change back. They did not report finding the particles. Instead, they worked out how strongly the particles could affect the light and still fit what they saw. The answer depends on their ideas about where the light comes from, especially how strong the magnetic field is there.
Chen Zhang
AstronomerThe authors investigate whether a strong first-order hadron–quark transition, with phase conversion slow relative to radial oscillations, can produce extended stable hybrid branches that accommodate anomalous compact-star constraints. HESS J1731–347 and XTE J1814–338 favor unusually small radii at low mass, whereas GW190814’s secondary appears too massive for an ordinary neutron star under GW170817-based maximum-mass inferences. A parameter scan of hadronic and hybrid branches, using a piecewise-polytropic benchmark supplemented by an independent speed-of-sound parametrization comparison, identifies two viable scenarios consistent with GW170817 and NICER constraints. In Scenario 1, one equation of state accommodates the GW190814-scale mass and HESS J1731–347 on its pure hadronic branch, and XTE J1814–338 on its slow stable hybrid branch. Scenario 2 retains the GW190814-scale hadronic branch but accommodates both small-radius objects on slow stable hybrid branches in very different transition-strength regimes. These are theoretical compatibility results, not observational confirmation of quark matter or slow phase conversion.
PublicSome compact-star observations are difficult to explain with conventional neutron-star models: two objects favor unusually small sizes for their low masses, while another appears too massive under limits inferred from GW170817. The researchers explored models in which matter inside a neutron star undergoes a sharp transition from hadronic matter to quark matter. If that conversion happens slowly compared with the star’s radial pulsations, additional configurations containing both kinds of matter can remain stable. Their model search found two ways to accommodate the unusual objects while respecting other observational constraints. One uses a single description of matter to explain the massive object and one small-radius object without quark matter, and the other small-radius object with a quark-containing interior. The second places both small-radius objects on quark-containing branches, in very different transition-strength regimes, while retaining a hadronic branch that reaches the high mass. These possibilities do not establish what the observed objects actually contain.
Young explorerSome tiny, very heavy stars seem smaller or heavier than scientists expected. The scientists tried different rules for how the stuff inside these stars might behave. In their models, some of that stuff can change into another kind called quark matter. If it changes slowly enough compared with the star’s in-and-out wobbling, more kinds of stars can stay steady. They found two possible ways to make their models fit the observations. But this does not prove that the real stars have quark matter inside.
Laura Olivera-Nieto, Fraser J. Cowie, Sera Markoff+2 more
AstronomerThe authors augment black-hole X-ray binary catalogues with radio and gamma-ray information, test rank correlations involving >100 TeV gamma-ray luminosity, and compare binary positions with unassociated sources in 1LHAASO and 1HGPS. They find no correlation with compact-object mass, companion mass, or inclination. Apparent strong correlations with radio and hard-state X-ray luminosities are not yet statistically significant because gamma-ray detections are few. An outburst duty cycle >20% is tentatively suggested as a requirement for >100 TeV gamma-ray loudness. Outside LHAASO sky coverage, spatial proximity to unassociated gamma-ray sources has >3σ significance only for the subset of binaries with reported radio detections; this does not establish individual source associations. The authors infer that radio-bright, high-duty-cycle systems are more likely gamma-ray detections and interpret the emission as linked to particles accelerated in jets or through jet–environment interactions. Their possible contribution to PeV cosmic rays remains unestablished.
PublicA few black holes orbiting companion stars have been detected emitting very energetic gamma rays. To investigate what makes these systems stand out, researchers compared their gamma-ray brightness with other properties. Gamma-ray brightness appears to track radio brightness and X-ray brightness in the hard state, but too few systems have gamma-ray detections to establish these relationships statistically. The study also hints that systems spending more than 20% of their time in outburst may be especially likely to emit gamma rays above 100 TeV. No relationship was found with either star's mass or the system's viewing angle. In the sky outside LHAASO coverage, binaries detected in radio lie near unidentified gamma-ray sources more often than expected by chance, with statistical significance above 3σ; proximity alone does not identify them as the same sources. The findings suggest, rather than prove, that jets produce the gamma-ray-emitting particles, either within the jets or where they interact with surrounding material.
Young explorerSome black holes with a nearby star send out light with a huge amount of energy, called gamma rays. Scientists looked for clues about which ones do this. The ones that shine brightly in radio waves and have active bursts more often seem more likely to make these gamma rays. But scientists have found too few to be sure of that pattern. They think fast streams of material called jets may help make the gamma rays, either inside the streams or where they hit nearby material.
Paulo C. C. Freire, Colin J. Clark, Cees G. Bassa+4 more
AstronomerPSR J0435+3233 has an unusually large apparent spin-down rate for a millisecond pulsar. The authors propose that varying acceleration from a wide tertiary orbit explains this anomaly. A hierarchical-triple model fits the radio and gamma-ray timing observations and enables detection of gamma-ray pulsations back to the start of Fermi LAT data in 2008. The intrinsic spin-down remains covariant with outer-orbit parameters, but large intrinsic rates are excluded: it is at least two orders of magnitude below the apparent rate, consistent with other Galactic MSPs. The authors identify a star 11 mas from the pulsar position as the tertiary’s optical counterpart. Its colours and inferred distance of 1.5–2.5 kpc suggest a 1.2-solar-mass F-type main-sequence star. The inferred outer orbit has e ≈ 0.6 and a period of about 70 years, likely at low inclination. They conclude that the system is a hierarchical triple. Future spectroscopy and astrometry are expected to provide mass-ratio and inclination estimates; continued timing may constrain Strong Equivalence Principle violations more tightly than current limits from PSR J0337+1715.
PublicThe rapidly spinning pulsar PSR J0435+3233 appeared to be slowing down much faster than similar pulsars. The researchers explain this by placing its existing binary system in a wider orbit with a third star: changing motion along our line of sight can mimic unusually rapid slowing. Their three-body model fits radio and gamma-ray observations and reveals gamma-ray pulses in data extending back to 2008. Although the pulsar’s true slowing rate is still uncertain, the analysis puts it at least 100 times below the apparent rate, making it consistent with similar pulsars. The team identifies a nearby-looking star as the third companion and infers that it has about 1.2 times the Sun’s mass and follows an elongated orbit lasting roughly 70 years. They conclude that this is a triple system. Further observations could clarify its geometry and potentially improve a test of the Strong Equivalence Principle, a fundamental principle of gravity.
Young explorerA spinning star seemed to be slowing down much too fast. Scientists think another star is tugging on it and its partner, changing how they move and making the slowdown look bigger than it really is. Their explanation matches the signals they measured. They conclude that three stars belong to this system, but they still need more observations to learn exactly how the stars move.
Aaron A. Maldonado, Alberto Domínguez, Adithiya Dinesh+4 more
AstronomerThe authors search 101 seven-day-binned Fermi-LAT repository light curves with a Fast Template Periodogram using sinusoidal, Gaussian-burst, and empirical asymmetric templates, calibrating significance against red-noise simulations with a Poisson noise floor. After quality cuts, three sources exceed 3 sigma per source, compared with 0.14 expected by chance, but none remains above 3 sigma after correction for the 101 light curves searched. These include the established candidate PG 1553+113; no new periodicity is detected. For 4FGL J0102.8+5824, significance changes from 0.24 sigma with a sinusoid to 3.85 sigma with a Gaussian burst, although simulations predict such a gain for about one noise source. About 40 percent of sources favor a sinusoid. The significance distribution has a heavier upper tail than the Gaussian null predicts, consistent with flares. A Random Forest classifier using periodogram, phase-coherence, and period-stability features also responds to isolated flares, exposing limitations of the null model. Unconstrained likelihood fits in a few bins can flatten periodograms and make the simulated null effectively white. The authors emphasize the LCR convergence criterion plus a consistency check, particularly for seven-day bins: non-sinusoidal templates complement standard searches, but a large significance gain alone does not establish periodicity.
PublicDo gamma-ray blazars brighten on a repeating schedule, or can irregular flares merely look periodic? The researchers examined 101 Fermi-LAT brightness records, comparing smooth repeating waves with patterns shaped like bursts and uneven flares. They tested the apparent signals against simulated random variability. After data-quality checks, three sources looked notable individually, but none cleared the authors' significance threshold once the full set of 101 searches was taken into account. Changing the assumed repeating shape could greatly strengthen a signal, yet simulations showed that a similarly large improvement can arise from noise. A machine-learning classifier also reacted to isolated flares, suggesting that the simulations do not fully represent flare behavior. The study reports no new periodicity detection and highlights the importance of checking data quality and testing multiple possible brightness patterns without mistaking a stronger-looking signal for proof.
Young explorerThe scientists watched bright things in space to see whether they flashed again and again like a blinking light. They tried different flash shapes and checked whether random changes could fool them. Some looked promising, but none passed all their checks for a new repeating pattern. One big flash can look like part of a pattern, so they need to be careful.
Sagnik Chatterjee, Mikhail V. Beznogov, Dany Page+1 more
AstronomerThis numerical study investigates neo-neutron stars, an intermediate stage between hot, lepton-rich compact remnants and cold, deleptonized neutron stars. Such a stage can follow core collapse, accretion-induced white-dwarf collapse, or a binary neutron-star merger if the remnant does not immediately form a black hole. Previous simulated temperature profiles suggest that the core initially has approximately the composition and mechanical structure of a cold neutron star, whereas the crust is expected to evolve during cooling. Using an extended neo-NSCool code, the authors model temperature-dependent equations of state and compositions throughout the crust. Their calculations find that thermally dripped neutrons slightly delay cooling during early thermal relaxation. Equations of state favoring exotic light species in the deepest crust yield significantly slower photon-era cooling than those favoring massive nuclei. Crustal composition also affects crystallization and contraction, with light-nucleus models keeping the innermost crust liquid longer. These are model results, not reported observations.
PublicA young neutron star passes through a cooling stage before becoming a cold neutron star. During this stage, earlier computer simulations suggest that its core already resembles a cold star's core, but its outer layers can still change their composition and structure. The researchers used computer models to study how these outer layers respond to cooling when their material properties depend on temperature. In the models, neutrons released by heat slightly slow the early cooling. Later, when cooling is dominated by emitted light, models with unusual lightweight ingredients deep in the crust cool substantially more slowly than models favoring heavy atomic nuclei. The ingredients also affect how the crust solidifies and shrinks: lightweight nuclei keep its deepest layers liquid longer. These findings describe simulated stars rather than direct observations.
Young explorerScientists used a computer to study how a young neutron star cools down. They tried different kinds of ingredients in its outer shell. In their models, some lighter ingredients made the star cool more slowly later on and kept the deepest part of its shell liquid for longer than heavier ingredients did. This is what happened in the computer models, not something they watched happen to a real star.
Jake Rule, Andrew Mummery, Steven Balbus+2 more
AstronomerThe authors test analytic descriptions of the plunging region in thin black-hole accretion discs against dedicated 3D global general relativistic MHD simulations using ATHENAK across black-hole spins. Simulated inflow closely approximates a gravity-dominated geodesic plunge, with the strongest agreement at low spin, while the thermodynamic framework agrees well across the spin range. A new magnetic-field model assumes flux freezing into a prescribed geodesic inflow; it broadly matches the simulations, although discrepancies suggest some non-ideal MHD dissipation. Simulated plunging-region MHD stress increases with increasing prograde spin. The reported spin–stress relation is approximately orthogonal to the degeneracy between low-stress, high-spin and high-stress, low-spin solutions in X-ray spin inference, suggesting that this degeneracy is not fundamental. The authors explicitly illustrate this for M33 X-7. These conclusions derive from model–simulation comparisons, rather than new observational measurements.
PublicResearchers used computer simulations to test models of gas plunging toward a black hole from a thin surrounding disc. In the simulations, the gas moves much as expected if gravity dominates, especially for slowly spinning black holes. Their model of the gas’s thermal behavior also agrees well with the simulations. A new model treats magnetic fields as carried along with the falling gas; it mostly works, but differences suggest some magnetic energy dissipation beyond that assumption. The simulations show stronger magnetic and fluid stresses as the black hole spins more strongly in the disc’s direction. This matters because different combinations of spin and stress can look alike in X-ray measurements. The simulated relationship suggests that this ambiguity need not be unavoidable, as the authors illustrate for M33 X-7.
Young explorerScientists made computer models of gas falling toward a black hole. The pretend gas mostly fell as gravity would make it fall. They also tried a rule for how magnetic fields travel with the gas. It worked pretty well, but not perfectly. Their models suggest that understanding the gas’s pushes and pulls could help scientists tell how fast a black hole spins.
Rin Oikawa, Yuri Sato
AstronomerOnly a small fraction of the several hundred identified tidal disruption events launch relativistic jets. These outflows are thought to be Poynting-flux dominated and powered by the Blandford-Znajek mechanism, but the origin of the plasma needed for their observed prompt emission remains unresolved. The authors propose plasma loading through magnetic reconnection near the black hole during super-Eddington accretion. In this scenario, accumulated magnetic flux produces an equatorial current sheet, where reconnection generates high-energy gamma rays. The authors show that photon-photon interactions can supply enough particles to account for the prompt emission while allowing the jet to remain magnetically dominated out to the emission region. They also show that magnetic dissipation can reproduce the observed prompt-emission properties within this framework. Predicted MeV and GeV gamma-ray flares offer a future observational test; the proposed loading mechanism is not presented as observationally established.
PublicWhen a star passes too close to a black hole, tidal forces can tear it apart. A small fraction of these events produce jets moving close to the speed of light, but how those jets acquire the particles needed to produce their early light remains uncertain. This study proposes that magnetic fields near the black hole rearrange and release energy as high-energy gamma rays. Interactions between these rays would then create particles that feed the jet. The authors show that this proposed process can supply enough particles and explain the observed early emission while the jet remains powered mainly by magnetic energy. The explanation still needs testing: it predicts gamma-ray flares that future observatories could look for.
Young explorerA black hole can pull so hard on a nearby star that it tears the star apart. Sometimes, a very fast stream of tiny particles shoots out from near the black hole. Scientists have an idea about where those particles come from: changing magnetic fields could make powerful light, and that light could make particles. Their idea predicts special flashes of light that future telescopes could look for to test whether it works.
E. Aydi, P. Craig, K. V. Sokolovsky+10 more
AstronomerThe study applies the observed correlation between GeV gamma-ray luminosity and interacting-outflow velocity contrast in classical novae to the anticipated eruption of T Coronae Borealis, comparing it with the 2021 eruption of RS Ophiuchi, the only nova securely detected at TeV energies. The authors argue that T CrB may occupy the extreme high-velocity-contrast end of the nova population, with its strongest shock arising where ejecta encounter the slow circumbinary medium. They therefore identify the external shock as the most likely site of possible TeV emission; GeV emission could include both external shocks and internal shocks, if present. T CrB's closer distance relative to RS Oph favors TeV detection, while neutrino prospects remain more uncertain because of their sensitivity to circumbinary density and structure. From the observed scatter in better-sampled recurrent novae, the authors infer a representative population-scale recurrence time of approximately 80 ± 12 years. These arguments identify T CrB as a promising candidate for the first securely established multi-messenger nova, not an already demonstrated case.
PublicT Coronae Borealis is a star system expected to undergo another nova eruption. Observations of other novae show that stronger gamma-ray emission is associated with a larger speed difference between colliding flows of material. Applying that relationship, the researchers suggest that fast material from T Coronae Borealis could hit slower material surrounding the system and produce especially powerful shocks. Those outer collisions are the proposed source of any very-high-energy gamma rays; lower-energy gamma rays could also come from collisions within the erupting material, if those occur. The system is closer than RS Ophiuchi, the only nova securely detected at the higher gamma-ray energies, making it a favorable target. Detecting neutrinos as well is a promising but less certain possibility, depending strongly on the surrounding material. The researchers also estimate a typical repeat-eruption interval of about 80 ± 12 years from better-studied recurring novae; this is a population-based estimate, not an exact eruption date. T Coronae Borealis could become a nova confirmed through multiple kinds of cosmic signals, but that has not yet been established.
Young explorerT Coronae Borealis is a star system that scientists expect to erupt again. They think fast-moving material from the eruption might crash into slower material around it. Those crashes could make very energetic light called gamma rays. Scientists might also catch tiny particles called neutrinos, but that is less certain and depends on what surrounds the star system. Because it is closer to us than another nova seen making very energetic gamma rays, it is a good place to look. These are ideas about what might happen, not things scientists have already seen from its next eruption.
Onic I. Shuvo, Eileen T. Meyer, Sibasish Laha+10 more
AstronomerMultiwavelength radio observations of the changing-look AGN 1ES 1927+654 following renewed X-ray brightening since mid-2022 trace its emerging jet and polarization evolution. VLBA imaging continues to show a bipolar jet, with X-band detections at larger separation and a K-band emission bridge consistent with a continuous outflow. The core has a GHz-peaked spectrum; VLA/VLITE measurements spanning 340 MHz–45 GHz indicate an inhomogeneous synchrotron source, self-absorbed below approximately 3 GHz and optically thin above. Agreement between VLA and VLBA flux densities above 8 GHz indicates compact-core dominance. Linear polarization is detected above approximately 3 GHz, increasing from about 0.2% to 6% with frequency, while electric-vector position angles depart from a linear wavelength-squared relation. In 2026, X-band monitoring recorded a smooth position-angle rotation of approximately 137 degrees over 81 days, followed by a partial return, with stable total intensity and fractional polarization below approximately 1.4%. This behavior is consistent with, but does not uniquely establish, a propagating disturbance crossing the compact emitting region. Circular polarization was not detected. The authors conclude that the source has transitioned from an X-ray-dominated, non-jetted state to a radio-loud AGN hosting a newly launched relativistic jet.
PublicRadio observations of the active galaxy 1ES 1927+654 reveal two oppositely directed jets after its X-ray emission began brightening again in mid-2022. Images also show a bridge of radio emission that is consistent with a continuous outflow. At higher radio frequencies, most of the measured emission comes from a compact central region. The researchers detected polarized radio waves, whose preferred orientation changed smoothly by about 137 degrees over roughly 81 days in 2026 before partly turning back. The total radio brightness remained steady during this change. A disturbance moving through the emitting region could explain the pattern, but that interpretation is not uniquely established. The authors conclude that the galaxy has changed from an X-ray-dominated state without a jet to a strong radio source with a newly launched, very fast jet, offering a way to study how jets and their magnetic fields develop.
Young explorerAstronomers used radio telescopes to watch a galaxy’s busy middle. They saw two streams shooting out in opposite directions. The radio waves changed the direction they wiggle, even while their brightness stayed steady. Something moving through the bright middle might explain that change. The scientists think they are watching a new pair of very fast jets grow.
Ayush Garg, Ritik Kumar, Maria G. Dainotti+3 more
AstronomerThis study benchmarks four reconstruction approaches on a parent sample of 545 Swift-XRT GRB afterglows: a physics-informed neural network (PINN) with seven afterglow-motivated priors, ReFANN, a Siamese dual-branch network with Monte Carlo dropout, and Polynomial Quantile Regression. Temporal sampling gaps limit empirical plateau constraints on the end time Ta, flux Fa, and post-plateau decay index alpha. All four approaches reduce fractional uncertainties in log Ta, log Fa, and alpha relative to the original observations. The broken-power-law PINN achieves the largest reductions, approximately 41–49%, but has an approximately 15–20% outlier rate. The other three methods yield smaller reductions of approximately 19–27%, with outlier fractions at or below about 4%, across a wider range of light-curve morphologies. Reduced-chi-squared prior selection produces a morphological classification consistent with independent labels, but does not achieve the best single-prior uncertainty reduction. These reconstruction results could strengthen plateau-based cosmological correlations; they do not establish improved cosmological constraints.
PublicGaps in observations make it harder to measure how the X-ray glow after a gamma-ray burst changes over time. Researchers compared four computer methods for reconstructing these brightness records, using a parent sample of 545 bursts observed by Swift-XRT. All four reduced the reported uncertainties in quantities describing when a relatively steady phase ends, its brightness, and how rapidly the glow then fades. The method giving the biggest uncertainty reductions, about 41–49%, also produced more outliers, about 15–20%. The other methods gave smaller reductions, about 19–27%, but outlier rates of about 4% or less. These are reconstructions, not new observations filling the gaps. More precise measurements could help researchers use gamma-ray bursts to study the universe, but this study benchmarks the reconstruction methods rather than demonstrating better cosmological measurements.
Young explorerAfter a huge flash in space, a glow slowly fades. Sometimes our pictures of that glow have missing parts. Scientists tested four computer helpers that try to work out what happened in those gaps. All four made the measurements less uncertain. But the helper that made them most precise also gave more unusual answers. The computers are making estimates, not taking new pictures.
Qi-Ling Chen, Ming-Ming Kang, Kun Fang+2 more
AstronomerThe study interprets the cutoff at tens of TeV in HAWC observations of the Geminga gamma-ray halo using two scenarios. In the first, the cutoff reflects the maximum electron energy attainable in the central pulsar wind nebula (PWN). A spherically symmetric diffusive shock acceleration model sets this limit through the upstream scale of the PWN termination shock. The proposed alternative invokes a rapidly increasing electron diffusion coefficient at high energies in the surrounding interstellar medium: high-energy gamma-ray emission extends beyond the analysis region, producing an apparent spectral cutoff. Both scenarios reproduce the Geminga cutoff, so this agreement alone does not establish its origin. Their distinct predictions for pulsar-halo cutoff statistics and corresponding PWN X-ray spectral features could be tested with further observations.
PublicHAWC observations of the gamma-ray glow around the Geminga pulsar show a cutoff at very high energies. This study finds that two different explanations can reproduce that feature. One is that the pulsar's surrounding wind nebula cannot accelerate electrons beyond a certain energy. Alternatively, the highest-energy electrons might spread much more rapidly through nearby space, placing a substantial share of their gamma-ray emission outside the region used for the analysis. The measured cutoff could therefore reflect either an acceleration limit or emission missed by the analysis. Neither explanation is established: future observations of other pulsar halos and X-ray emission from their wind nebulae could help distinguish them.
Young explorerScientists see a glow around a space object called Geminga. The glow fades at very high energies. They have two ideas: perhaps the electrons making the glow cannot get any more energetic, or perhaps they spread so far that some glow falls outside the area being checked. Both ideas fit what scientists see, but more observations are needed to tell which is right.
A. Tortosa, L. Zappacosta, E. Piconcelli+51 more
AstronomerThe authors analysed 28 luminous quasars at z ≃ 5.85–7.56, using 26 for correlation tests, to assess whether steep X-ray spectra are restricted to the most efficiently grown early SMBHs. The sample combines HYPERION, luminous non-HYPERION sources, and new XMM-Newton observations of moderately accreting SMBHs, extending coverage mainly toward lower growth efficiencies. Black hole masses and growth indicators were re-derived homogeneously, incorporating recent JWST spectroscopy. No statistically significant correlation was found between coronal spectral parameters and black hole growth indicators. The luminous quasars systematically exhibit steep X-ray continua, with high photon indices and/or low high-energy cutoffs, consistent with cold coronae; a connection to rapid accretion remains an interpretation. If steep spectra are common among early AGN, reduced count rates at fixed intrinsic luminosity could affect their detectability and bias future reionization-era AGN censuses.
PublicResearchers studied X-rays from 28 exceptionally bright quasars in the early universe, where gas feeds supermassive black holes. They tested whether a previously suggested connection between X-ray spectra and how efficiently the black holes had grown held up in a broader sample. Using 26 quasars for that test, they found no statistically significant connection. The quasars nevertheless consistently showed X-ray emission that falls off steeply toward higher energies, or has a low-energy cutoff at its high-energy end, or both. These features are consistent with relatively cool coronae, the innermost X-ray-emitting regions around the accreting black holes. Rapid gas accretion is a possible explanation, not an established cause. If such spectra are common among early active black holes, future X-ray surveys could detect fewer photons from them at the same intrinsic brightness, making some harder to find and affecting estimates of their population.
Young explorerScientists looked at X-rays from 28 very bright places around giant black holes when the universe was young. They found that the strongest-energy X-rays tended to fade away. That could mean the glowing material near the black holes is relatively cool. They also checked whether the X-rays were linked to how efficiently the black holes had grown, but did not find a clear link. If many young black holes shine this way, future X-ray searches might have a harder time finding them.
Rami Z. E. Alsaberi, Zachary J. Smeaton, Miroslav D. Filipovic+5 more
AstronomerATCA and MeerKAT radio continuum observations of the Large Magellanic Cloud supernova remnant N 132D show radio–X-ray spatial correlations in the central and left regions and the right shell, suggesting a close connection between thermal and non-thermal plasma. Polarisation indicates predominantly radial magnetic fields, with mean fractional polarisations of 1.2%, 3.0%, and 4.0% at 2100, 5500, and 9000 MHz, respectively. A double-peaked Faraday depth spectrum suggests regions with different magnetisation properties or magnetic-field geometries. ATCA rotation measures average approximately 2 rad m^-2 and reach approximately 338 rad m^-2. Under a constant-partition assumption for electron and magnetic-field energy densities, the authors estimate a magnetic field of approximately 90 microG and a minimum energy of 3 x 10^50 erg. The integrated radio spectrum is a power law with spectral index -0.74 ± 0.01. These observations constrain the remnant’s magnetic structure and energetics and inform interpretations of particle acceleration and shock evolution.
PublicAstronomers used the ATCA and MeerKAT radio telescopes to study N 132D, the remains of an exploded star in the Large Magellanic Cloud. Radio emission matches the locations of X-ray emission in several parts of the remnant, suggesting that its thermal and non-thermal material are closely connected. Measurements of radio polarisation indicate that the magnetic fields mainly point along directions extending outward from the centre. A two-peaked pattern in how the radio signal is affected by magnetised material suggests either different magnetic conditions in different regions or changes in the fields’ geometry. Assuming a particular relationship between the energy in electrons and magnetic fields, the researchers estimate a field strength of about 90 microgauss and a minimum energy of 3 x 10^50 erg. The findings help constrain how magnetic fields, accelerated particles, and expanding shocks behave in this remnant; the field strength and energy are model-dependent estimates rather than direct measurements.
Young explorerAstronomers looked at the leftovers of an exploded star called N 132D using telescopes that detect radio waves. Some places that shine in radio waves also shine in X-rays, which hints that different kinds of material there are connected. The radio waves give clues about invisible magnetic fields that mostly line up like spokes on a wheel. They also hint that the magnetic fields are not the same everywhere. The astronomers used these clues and some assumptions to estimate how strong the fields are and how much energy the leftovers hold.
Maxence Corman, Llibert Aresté Saló, Katy Clough
AstronomerFully nonlinear simulations of quasi-circular, comparable-mass black-hole binaries in shift-symmetric Einstein-scalar-Gauss-Bonnet gravity show an accelerated late inspiral and merger relative to general relativity, but a noticeably smaller acceleration than post-Newtonian (PN) predictions. Stationary black holes carry scalar charge in this theory, and scalar dipole radiation enters at −1PN order. PN calculations including corrections through 2PN predict faster inspiral, while conservative modifications can oppose that trend. The authors relate the reduced acceleration in their simulations to conservative dynamics: more energy must be radiated to produce a given frequency change during late inspiral. Longer signals may exhibit distinctive frequency evolution, although differences from GR are suppressed near merger. These simulation results suggest revisiting constraints that extend PN approximations to merger or neglect metric backreaction in order-by-order treatments; they are not observational evidence for modified gravity.
PublicThe researchers used computer simulations to study how two black holes spiral together in an alternative to Einstein’s general relativity. In this theory, black holes have an additional scalar charge and can lose energy through an extra kind of radiation, which tends to speed up their approach. The simulations show a faster merger than in general relativity, but less of a speed-up than approximate calculations predict. The authors link this to changes in the orbital dynamics: near merger, more energy must be radiated to produce the same change in orbital frequency. A longer signal might reveal a distinctive pattern, but the differences from Einstein’s theory become smaller close to merger. The work suggests that some existing limits on this alternative theory may need reassessment. It does not show that real black holes obey the alternative theory.
Young explorerTwo black holes can circle each other and come together. Scientists used a computer to try a different set of gravity rules. In their pretend black-hole dance, the holes came together sooner than with Einstein’s rules, but not as much sooner as simpler maths had suggested. Near the end, the two dances looked more alike. This may mean scientists need better calculations when checking the new rules. It does not mean those rules are how real black holes behave.
Run-Min Yao, Xiao-Jun Bi, Peng-Fei Yin+1 more
AstronomerThis theoretical study identifies driven photon–axion mode conversion in a magnetic field within a coherent, oscillating axion dark-matter background. Periodic birefringence continuously rotates photon polarization, driving magnetic photon–axion mixing. A Floquet treatment yields resonances when integer harmonics of the axion oscillation frequency compensate the dispersion mismatch: Delta_gamma − Delta_a approximately equals n m_a, with integer n. Efficient conversion can therefore occur far from conventional level crossing, but the resonance disappears if the periodic drive is averaged out of the propagation Hamiltonian. Conversion remains bounded and unitary, rather than representing parametric instability or axion decay. The authors predict characteristic polarization signatures and illustrate them in a blazar environment; the abstract reports no observational detection.
PublicThe researchers calculate a possible way for light to turn into axions, hypothetical particles that could make up dark matter. In their model, a coherently oscillating axion background repeatedly rotates light's polarization as it travels through a magnetic field. This periodic influence can bring light and axions into resonance, allowing efficient conversion under conditions where the usual resonance would not occur. Averaging away the oscillations would miss this effect. The conversion stays bounded rather than growing unstably, and it is not axion decay. The study predicts distinctive polarization patterns and illustrates the idea in a blazar environment, but does not report observing the effect.
Young explorerImagine light traveling through invisible stuff that wiggles in a steady rhythm. Scientists calculated that, if this stuff is made of tiny particles called axions, its wiggles and a magnetic field could help light change into axions. The rhythm must match just right. This is a prediction, not something they report seeing.
Rafael Bán Jacobsen, Ricardo Luciano Sonego Farias, Veronica Dexheimer
AstronomerThis theoretical study presents the first finite-temperature extension of the Many-Body Forces (MBF) Model, a relativistic quantum hadrodynamics framework with field-dependent nuclear interaction couplings. It assumes charge-neutral, beta-equilibrated matter containing the baryon octet, electrons, muons, and neutrinos. The authors vary the many-body-force parameter, temperature, and three hyperon coupling schemes newly introduced into MBF, examining the speed of sound, compressibility, and adiabatic index. They calculate neutron-star and protoneutron-star mass–radius relations using the Tolman–Oppenheimer–Volkoff equations at zero and finite temperature, including fixed-entropy-per-baryon and fixed-lepton-fraction scenarios. Within the model, the hyperon coupling schemes soften the equation of state by different amounts, requiring different but always nonzero many-body-force effects to reproduce observations. These are model results, not new observational measurements. Multidimensional result tables are available through CompOSE for use in astrophysical simulations.
PublicThe researchers extend a model of dense nuclear matter so it can account for temperature, helping them study neutron stars and their early, hot stage, called protoneutron stars. Their calculations assume a particular mixture of particles and conditions for electrical neutrality and particle equilibrium. They explore how temperature, interactions involving many particles, and three ways of describing interactions with particles called hyperons affect matter’s properties and the stars’ predicted masses and sizes. The different hyperon interaction choices make the matter less resistant to compression by different amounts. Matching observations within this model requires interactions involving many particles in every case, though their required strength varies. This is a theoretical study rather than a new observation; its result tables are available for other researchers’ simulations.
Young explorerScientists used math to study the tightly packed stuff inside neutron stars, including young, hot ones. They updated their model to include heat. Different choices about how tiny particles interact changed how easily the stuff could be squeezed. These are model calculations, not new pictures or measurements of stars.
Romeo Felice Rosato, Francesco Crescimbeni, Sophia Yi+2 more
AstronomerGreyRing models the frequency-domain post-merger signal of binary black-hole coalescences using the remnant’s graybody factor. In comparisons with a large set of comparable-mass, aligned-spin numerical-relativity waveforms, it achieves mismatches of order 10^-6 for the dominant (ℓ,m) = (2,2) mode and typically outperforms state-of-the-art time-domain models. The authors introduce a strong-gravity consistency test comparing GreyRing estimates of remnant mass and spin with standard black-hole spectroscopy estimates. The test uses only the post-merger signal, without requiring overtones or very early ringdown starting times. Applied to GW250114, GreyRing yields remnant mass and spin consistent with estimates from the full signal, with precision comparable to or slightly better than standard spectroscopy. The waveform accuracy is demonstrated against simulations; the event analysis reports parameter consistency rather than a detected departure from the expected behavior.
PublicAfter two black holes merge, the remaining black hole produces a fading signal called ringdown. The researchers developed GreyRing, a new model of this signal based on a property called the graybody factor. It closely matches a large collection of computer simulations of mergers with comparable masses and spins aligned with the orbit. They also propose a way to test gravity by comparing the final black hole’s mass and spin inferred with GreyRing against estimates from another ringdown method. For the event GW250114, GreyRing’s estimates agree with those obtained from the full signal, and their precision is comparable to or slightly better than the standard ringdown method. This agreement is a consistency finding, not evidence of a failure of gravity.
Young explorerWhen two black holes join together, the new black hole makes a fading ripple, a little like a bell ringing after it is struck. Scientists made a new way to describe that ripple and checked it against computer pretend-mergers. It matched very well. For one real event, it gave answers about the black hole’s size and spin that agreed with another way of checking. Scientists hope to use it to test gravity.
Peng Yang, Kilar Zhang
AstronomerThis theoretical study derives the angular eigenvalue problem for the extreme charged C-metric from a constrained five-point Fuchsian formulation of the non-extremal equation. The extreme limit is obtained by decoupling a hypermultiplet in the dual four-dimensional N=2 SU(2) × SU(2) linear quiver gauge theory. The authors derive the parameter dictionary and renormalized Matone relations, and explicitly connect the physical limit Q → M to quiver decoupling through a coordinate transformation. Regular endpoint conditions yield an algebraic quantization condition. Eigenvalues computed using a truncated instanton prepotential are tested against independent angular spectra near extremality and at larger acceleration; the abstract gives no quantitative assessment of those comparisons. The axisymmetric sector reproduces the known exact spectrum.
PublicThe researchers study a mathematical model called the extreme charged C-metric, focusing on the allowed values that describe its angular behavior. They connect this problem to a different theoretical framework, a gauge theory, and derive a rule for selecting the allowed values by requiring well-behaved solutions at the angular endpoints. They test approximate calculations against independently calculated spectra near the extreme limit and at larger acceleration, although the abstract does not state how closely those tests agree. For the case that is symmetric around an axis, their method recovers an already known exact answer. These are theoretical calculations, not astronomical observations.
Young explorerThe scientists worked on a tricky math puzzle about how a model behaves in different directions. They used another kind of math to find rules for which answers are allowed. They checked some approximate answers with a separate calculation. For one simpler version of the puzzle, they found the exact answers that were already known.
