Discovered just 6 billion years after the Big Bang, AT2025wet is the highest-redshift non-jetted tidal disruption event known, allowing researchers to probe the missing-energy puzzle.
The post Discovery of a Featureless Tidal Disruption Event at <em>z</em> βΌ 1 with the Wide Field Survey Telescope appeared first on AAS Nova.
The disks around young high-mass stars survive for roughly 3.72 million years, and those around low-mass stars survive for 7.20 million years, though the distributions for both populations are quite broad.
The post Disk Lifetime Distribution as a Function of the Mass of Host Star appeared first on AAS Nova.
A recent Focus Issue of the Astrophysical Journal Letters describes the fourth version of the catalog of gravitational wave events (GWTC-4.0) from the Laser Interferometer Gravitational Wave Observatory (LIGO), the Virgo interferometer, and the Kamioka Gravitational Wave Detector (KAGRA).
This catalog contains transient gravitational wave events recorded through January 2024, during the observatoriesβ fourth observing run, which concluded in November 2025. GWTC-4.0 displays the results of significant improvements to our suite of gravitational wave detectors, including higher-powered lasers and reduced quantum noise. A fifth catalog of gravitational wave events was released in Spring 2026, with the accompanying scientific articles being submitted to the Astrophysical Journal and the Astrophysical Journal Letters.
This Monthly Roundup consists of short descriptions of each of the currently published research articles in the LIGOβVirgoβKAGRA Gravitational Wave Transient Catalog (GWTC): Release 4 Focus Issue. Each snippet links to the corresponding research article, and the Focus Issue landing page is linked at the bottom of this post. Be sure to revisit the landing page to catch new articles as theyβre published!
A timeline showing observing runs between 2015 and 2024. Click to enlarge. [LVK Collaboration 2025]
After these detectors record subtle spacetime squiggles from compact objects colliding millions to billions of light-years away, the collaboration converts the raw signals into the data contained in catalogs like GWTC-4.0. This process involves modeling the gravitational wave signals, filtering them to identify candidate transients, and pinpointing the most significant events.
After collecting and cleaning the signals, the collaboration undertakes a critical step: making their data accessible to researchers and the public. The data are available through the Gravitational Wave Open Science Center, and the Focus Issue article on open data describes how to navigate the online portal, how the datasets archived online are structured, and how the data were calibrated.
This fourth version of the gravitational wave transient catalog greatly expands the sample of gravitational wave transients recorded by detectors across the globe. Including events from previous catalogs, GWTC-4.0 brings us to 218 events for which the probability of the source being astrophysical in nature is more than 50% and for which there is little chance of the signal being an instrumental artifact. This represents a more than 100% increase in the number of recorded gravitational wave events fulfilling this criterion, broadening our understanding of colliding compact object pairs. This release also includes some superlative signals, such as the most massive black hole binary with a low false-alarm rate and the highest signal-to-noise ratio for a gravitational wave event thus far.
Detected in November 2023 by both LIGO Hanford and LIGO Livingston, GW231123 is in many ways an exceptional gravitational wave transient. The total mass of the merging components appears to be between 190 and 265 solar masses, and the false-alarm rate for this signal is less than one per year. This makes it the most massive merger event with such a low false-alarm probability. The two components also appear to have high spins, which complicates the interpretation of the signal with existing models. A binary black hole merger in which one or more components lies within the pair-instability mass gap is the likeliest explanation for this signal, but the authors also present alternative scenarios, such as a core-collapse supernova or a gravitationally lensed gravitational wave signal.
Representations of the GW230814 gravitational wave signal. Click to enlarge. [LVK Collaboration 2026]
Plot of the differential merger rate as a function of the mass of the more massive of the two merger components. This shows overdensities at 10, 35, and possibly 20 solar masses. Click to enlarge. [LVK Collaboration 2026]
The full list of articles in the GWTC-4.0 Focus Issue can be found here.
βGWTC-4.0: An Introduction to Version 4.0 of the Gravitational-Wave Transient Catalog,β A. G. Abac et al 2025 ApJL 995 L18. doi:10.3847/2041-8213/ae0c06
βGWTC-4.0: Methods for Identifying and Characterizing Gravitational-Wave Transients,β A. G. Abac et al 2026 ApJL 1004 L21. doi:10.3847/2041-8213/ae447b
βOpen Data from LIGO, Virgo, and KAGRA Through the First Part of the Fourth Observing Run,β A. G. Abac et al 2026 ApJ 1004 232. doi:10.3847/1538-4357/ae211e
βGWTC-4.0: Updating the Gravitational-Wave Transient Catalog with Observations from the First Part of the Fourth LIGOβVirgoβKAGRA Observing Run,β A. G. Abac et al 2026 ApJL 1004 L22. doi:10.3847/2041-8213/ae2c74
βGW231123: A Binary Black Hole Merger with Total Mass 190β265 Mβ,β A. G. Abac et al 2025 ApJL993 L25. doi:10.3847/2041-8213/ae0c9c
βGW230814: Investigation of a Loud Gravitational-Wave Signal Observed with a Single Detector,β A. G. Abac et al 2026 ApJL 1004 L23. doi:10.3847/2041-8213/ae2ad3
βGWTC-4.0: Population Properties of Merging Compact Binaries,β A. G. Abac et al 2026 ApJL 1005 L51. doi:10.3847/2041-8213/ae771e
The post Monthly Roundup: The Fourth Catalog of Gravitational Wave Events from LIGO, Virgo, and KAGRA appeared first on AAS Nova.
Researchers have discovered a supernova that occurred when the universe was roughly 5 billion years old; if the supernovaβs luminosity is similar to that of nearby events, it must have been magnified by a factor of 250.
The post A Natural β³100Γ Telescope: Discovery of the Strongly Lensed Type II SN 2025mkn at <em>z</em> = 1.37 appeared first on AAS Nova.
Of 7,229 flares from 1,430 stars, most came from stars with temperatures below 4000K and rotation periods shorter than 4 days; most flares lasted less than 2 hours.
The post Magnetic Activity in X-Ray Stars from eROSITA: Insights from the TESS and LAMOST Surveys appeared first on AAS Nova.
An unusual clump of gas 450 million years after the Big Bang may contain stars hailing from the universeβs elusive first generation of stars. New research examines an alternative explanation involving an accreting black hole.
Hebe is visible in the image on the left as a prominent blob of helium emission up and to the left from GN-z11, a luminous galaxy hosting an accreting supermassive black hole. On the right is an infrared image of the same region, in which Hebe is not visible. Click to enlarge. [Adapted from NASA, ESA, CSA, Ralf Crawford (STScI)]
Before the community settles on this exciting explanation, however, the hypothesis must withstand all the tests astronomers can throw at it. In a recent research article, Junehyoung Jeon, Tae Bong Jeong, and Saiyang Zhang (The University of Texas at Austin) along with Volker Bromm (The University of Texas at Austin) attempted to explain Hebeβs properties in another way.
Hebe glows with distinctive helium emission that requires a source of high-energy radiation. This radiation could be provided by a cluster of Pop III stars, but it could also, in theory, arise from an accreting supermassive black hole embedded within the gas clump.
Predicted total mass of Hebeβs Pop III stars as a function of the LymanβWerner flux from the nearby galaxy GN-z11. Click to enlarge. [Jeon et al. 2026]
While the black hole scenario could, with reasonable black hole masses, gas densities, and accretion rates, reproduce individual flux measurements drawn from JWST observations, this hypothesis struggled to simultaneously match multiple measurements. The Pop III star cluster scenario, with a cluster mass of a few hundred thousand solar masses, provided the best fit to the JWST data.
Modeled spectral energy distributions (lines) and predicted line flux densities (open symbols) for the accreting black hole, Pop III star, and Pop II (second-generation) star hypotheses. The observed JWST line fluxes are shown as filled circles. Click to enlarge. [Jeon et al. 2026]
While a cluster of Pop III stars is still the leading explanation for Hebeβs properties, the team noted that the Pop III star and black hole hypotheses arenβt mutually exclusive; Hebe could very well harbor a primordial black hole and a smattering of Pop III stars. Regardless of what powers its characteristic helium emission, Hebe offers an enticing glimpse into the early universe, and more work is needed to understand this intriguing object.
βWhat Is Powering the Enigmatic He II Emitter Hebe: The First Stars or Black Holes?β Junehyoung Jeon et al 2026 ApJ 1006 27. doi:10.3847/1538-4357/ae7bea
The post First-Generation Stars Provide Better Fit than a Black Hole for Early-Universe Gas Clump appeared first on AAS Nova.
An analysis of the fourth gravitational wave catalog supports the existence of a gap at 45 solar masses in the secondary black hole mass distribution, among other findings.
The post Trends in the Population of Binary Black Holes Following the Fourth Gravitational-Wave Transient Catalog: A Data-Driven Analysis appeared first on AAS Nova.
According to calculations, in a 4-year period researchers may detect of order one compact binary system in which the binaryβs inspiral and the spin of its neutron star component both produce gravitational waves.
The post An Enhanced Formation Channel for Galactic Dual-Line Gravitational-Wave Sources: von ZeipelβLidovβKozai Effect in Triples Involving Sgr A* appeared first on AAS Nova.
Unlike traditional βshift and stackβ algorithms, a newly developed asteroid-detection method requires no assumptions on speed or direction; this method can be applied to upcoming time-domain surveys.
The post Trajectory-Agnostic Asteroid Detection in TESS with Deep Learning appeared first on AAS Nova.
Researchers have detected molecules containing rings and chains of carbon atoms in the vicinity of a rare pair of quasars. The trends in the distribution of these molecules are unexpected, suggesting that more work is needed to understand the conditions surrounding active supermassive black holes.
Examples of aromatic and aliphatic hydrocarbons. Benzene (top left) is the simplest aromatic molecule. Propane (top right) is a simple aliphatic molecule. Propylbenzene (bottom) is an aromatic molecule with an aliphatic chain branching off of it. In these βskeletalβ formulae, there is a carbon atom at each vertex, and the remaining atoms (not depicted) are all hydrogens. Single lines indicate single chemical bonds, and double lines indicate double bonds. [Wikipedia; Public Domain]
JWSTβs sensitive infrared eyes have allowed researchers to study the distribution, creation, and destruction of both aromatic (containing one or more rings of carbon atoms in which certain electrons spread out within the ring) and aliphatic (containing chains of carbon atoms) hydrocarbons. These molecules have been spotted in a wide array of environments, and now, astronomers are finding them in more distant and more extreme environments than ever before.
SDSS J074922.96+225511.7, or J0749+2255 for short, is a quasar pair seen 3 billion years after the Big Bang. The two feasting supermassive black holes are roughly 12,000 light-years apart, giving researchers a glimpse into the late stages of a galaxy merger and a harsh environment in which to study the survival and destruction of molecules.
Researchers studying J0749+2255 with JWST have previously reported the detection of a 3.3-ΞΌm emission feature from aromatic molecules. Now, C. E. Mentzer (University of Missouri), Aigen Li (University of Missouri), and Xuejuan Yang (Xiangtan University) have analyzed JWST spectra of J0749+2255 and found not just widespread aromatic emission at a rest-frame wavelength of 3.3 ΞΌm, but also aliphatic emission at 3.4 ΞΌm, which they attribute to carbon chains branching off from the aromatic molecules. This likely makes J0749+2255 the most distant galaxy in which both aromatic and aliphatic emission has been detected.
Aliphatic fractions in the bright central region surrounding the two quasars (top) and in the outer regions (bottom). [Mentzer et al. 2026]
Mentzer, Li, and Yang subdivided the observations into 47 regions and measured the strength of the 3.3- and 3.4-ΞΌm features in each region. This analysis found strong aromatic emission nearest the quasars and showed that the fraction of carbon atoms bound up in aliphatic chains is highest close to the quasars.
Both of these findings are unexpected: the harsh radiation environment near the two active black holes is thought to break apart chains of carbon atoms attached to aromatic rings (which should decrease the 3.4-ΞΌm emission) and possibly destroy small aromatic molecules (which should decrease the 3.3-ΞΌm emission) β yet both of these features are strongest near the quasar cores where the radiation should be most capable of molecular destruction.
The authors speculated that the analysis regions centered on the quasars are large enough that they contain gas that hasnβt been pummeled by the quasarsβ intense radiation and outflows, leaving molecules intact and able to produce the observed emission. However, this doesnβt explain the trend of stronger 3.3- and 3.4-ΞΌm emission closer to the quasars β necessitating further research into the emitting behavior of aromatic and aliphatic molecules under the extreme conditions of a dual quasarβs neighborhood.
βWidespread Detection of Aromatic and Aliphatic Emission in the Dual Quasar J0749+2255 at Cosmic Noon,β C. E. Mentzer et al 2026 ApJL 1005 L38. doi:10.3847/2041-8213/ae7e86
The post Researchers Spot Hydrocarbons Surprisingly Close to a Quasar Pair appeared first on AAS Nova.
Researchers show that the global martian dust storm in Mars year 34 warmed the lower atmosphere and led to greater electrical charging and stronger electric fields compared to a dust-free atmosphere.
The post Turbulence-Coupled Electrodynamics of the Martian Year 34 Global Dust Storm on Mars appeared first on AAS Nova.
Researchers show a connection between non-thermal hard X-ray emission and a tadpole-shaped downflow, strengthening the association between these flows and magnetic reconnection.
The post Nonthermal X-Ray Emission Associated with Supra-Arcade Downflows in the Late Decay Phase of a Solar Flare appeared first on AAS Nova.
Spectra of 3I/ATLAS as it retreated from its encounter with the Sun show that the cometβs mixing ratios of CN, C3, and C2 with respect to water are similar to those of solar system comets, while NH2 is depleted.
The post Postperihelion Optical Low-Resolution Spectroscopy of Interstellar Comet 3I/ATLAS appeared first on AAS Nova.
This image, which combines a background view from the Dark Energy Camera Legacy Survey with two inset images from the Very Large Telescope, shows an unusual pair of galaxies in the Fornax Cluster. The galaxies FCC 224 and FCC 240 are under scrutiny because they may have formed via a high-velocity collision between dwarf galaxies β the so-called βbullet-dwarfβ model. Using new spectroscopy from the Very Large Telescope, Maria LuΓsa Buzzo (Yale University) and collaborators analyzed the ages and kinematics of the galaxiesβ stars as well as the unusually bright globular clusters swirling around each galaxy. These data suggest that both galaxies are deficient in dark matter, and their stellar populations and globular clusters are all roughly 10 billion years old. The lack of dark matter and the uniform stellar ages are both consistent with the bullet-dwarf model, in which the collision strips away dark matter and ignites a burst of star formation. Since this type of collision can create more than two remnants, the team suggests searching along the trajectory defined by FCC 224 and FCC 240 for more fragments from the collision, some of which may contain the galaxiesβ lost dark matter. To learn more about these galaxies and what they might mean for the bullet-dwarf mechanism, be sure to check out the full research article linked below.
βDark-Matter-Deficient Twins: FCC 224 and FCC 240 as Possible Analogs of NGC 1052-DF2 and DF4,β Maria LuΓsa Buzzo et al 2026 ApJ 1005 15. doi:10.3847/1538-4357/ae7349
The post Featured Image: A Rare Pair of Galaxies Lacking Dark Matter appeared first on AAS Nova.
An analysis of synthetic starspot-crossing events suggests that while starspot longitudes are tightly constrained in high signal-to-noise data, other properties are more loosely determined.
The post Quantifying the Impact of Starspot-Crossing Events on Retrieved Parameters from Transit Lightcurves appeared first on AAS Nova.
Using data from JWST, the Subaru Telescope, and the Atacama Large Millimeter/submillimeter Array, researchers have identified a previously unseen collimated protostellar jet in a HerbigβHaro object.
The post A Study of HH 270 with the James Webb Space Telescope appeared first on AAS Nova.
White dwarfs often show signs of metals in their spectra, providing evidence that these evolved stars have accreted planetary material. Could white dwarf spectra also provide evidence for technological activity in these star systems?
When a Sun-like star reaches the end of its hydrogen-burning lifetime, it first puffs up into a red giant before exposing its white-hot core, which evolves into a white dwarf. This dramatic transition shakes up any planets that happened to be orbiting the star, and some close-in planets may end up crumbling apart, their rubbly remains peppering the surface of the white dwarf.
So far, astronomers have found hundreds of white dwarfs that appear to be polluted with heavy elements from their destroyed planets. These observations provide a valuable look into the bulk compositions of planetary materials outside our solar system. They may also provide a way to detect patterns of chemical abundances that are not natural, resulting from technological processes like industrial refining or the creation of alloys β in other words, a technosignatureΒ that is evidence of not just life, but technologically advanced life.
Representation of the chemical abundances of meteorites (pink, orange, and green) and white dwarfs (gray). Most white dwarf abundances overlap with the parameter space defined by the meteorite sample. Click to enlarge. [Huang et al. 2026]
The team used thousands of chemical abundance measurements from meteorites as a reference for the natural bulk composition of planetary material. For the mixture of natural and processed material, they combined the meteorite reference material with a template that is metal-rich and silicate-poor, with enhanced amounts of iron, nickel, chromium, and manganese.
Evidence for a model including technologically processed material relative to a purely natural model, as a function of the number of elements detected in the white dwarf. ndet = 0 indicates that only upper limits were obtained on elemental abundances. Higher Bayes factors indicate stronger evidence. The left-hand plot is based on abundances measured from the white dwarfsβ photospheres, while the right-hand plot uses abundances adjusted for diffusion within the white dwarf. Click to enlarge. [Adapted from Huang et al. 2026]
Ultimately, Huangβs team found that strong statistical support for the existence of technological processes was uncommon, though there were certain measurements in their sample of white dwarfs that were difficult to reconcile with a solely natural model.
Perhaps unsurprisingly, the team also found that the quality of the chemical abundance measurements affected the constraining power of the observation; some white dwarfs had upper limits for just a few elements, while others had definitive detections of many elements. They found that the most discerning observations recorded iron, magnesium, chromium, and titanium, plus either nickel, silicon, or sodium.
While this work didnβt dredge up firm evidence for technological activity, it provides a jumping-off point for future searches. The handful of white dwarfs in this sample that were fit poorly by a purely natural model could be compared against other technosignature models or targeted with high-resolution spectroscopy. Future measurements of iron and magnesium in polluted white dwarfs may be useful as a preliminary screening tool, helping to pick out intriguing targets for follow-up observations.
βA Calibrated Bayesian Search for Potential Chemical Technosignatures in Polluted White Dwarfs,β Bo-Lun Huang et al 2026 ApJ 1006 9. doi:10.3847/1538-4357/ae742c
The post Seeking Technosignatures in Polluted White Dwarfs appeared first on AAS Nova.
Researchers have discovered two chemically distinct populations in a sample of 97 metal-poor stars in the Milky Way halo, potentially providing a way to identify accreted halo stars.
The post Chemical Fingerprints of Accreted Ultrafaint Dwarf Galaxies in the Milky Way Halo appeared first on AAS Nova.
Analysis of blue straggler stars in 56 Milky Way globular clusters finds no evidence for a bimodal distribution in colorβmagnitude space due to differing formation pathways.
The post Revisiting the Evidence for Double Sequences of Blue Straggler Stars in Globular Clusters appeared first on AAS Nova.
By constructing a detailed distance map to the Magellanic Clouds, researchers have revealed substructures within this interacting galaxy pair, including an azimuthal warp in the Large Magellanic Cloud.
The post Warped and Hooked: Mapping the Magellanic Clouds in Three Dimensions Using Red Clump Stars appeared first on AAS Nova.
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