Sazuna/UAT_keywords huggingface dataset:
Kilonova Constraints for the LIGO/Virgo/KAGRA Neutron Star Merger Candidate S250206dm: GW-MMADS Observations. Gravitational-wave (GW) neutron star mergers with an associated electromagnetic counterpart constitute powerful probes of binary evolution, the production sites of heavy elements, general relativity, and the expansion of the Universe. Only a handful of candidate GW binary mergers during the fourth LIGO/Virgo/KAGRA observing run (O4) so far are believed to include a neutron star. We present optical─near-infrared follow-up observations of the candidate neutron star─black hole GW merger S250206dm. This is the first high-significance mass-gap neutron star─black hole candidate observed by multiple GW detectors (thus having a significantly smaller sky localization than one-detector events), offering the first opportunity to effectively follow up a GW event of this kind. Our GW MultiMessenger Astronomy DECam Survey (GW-MMADS) campaign consisted of a wide-field search using the Dark Energy Camera (DECam) and T80-South (T80S), as well as galaxy-targeted observations using the Southern Astrophysical Research (SOAR) imager and the Fraunhofer Telescope at Wendelstein Observatory. No viable kilonova counterpart was found in our observations. We use our observation depths to place competitive constraints on kilonova models similar to or brighter than the GW170817 kilonova AT 2017gfo within our observed fields, ruling out 100% of such models with SOAR galaxy-targeted observations and ∼43% (48%) with DECam (DECam and T80S).

Keywords: Gravitational wave astronomy, Transient detection
The Fraction of Distilled White Dwarfs with Long-lived Habitable Zones. After carbon and oxygen, 22Ne is the most abundant element in white dwarf (WD) interiors. As C/O WDs crystallize, they are predicted to go through a distillation process in the central layers if they have a sufficiently high 22Ne mass fraction of ≳2.5%. Observational evidence for distillation comes from an overdensity of WDs on the Q-branch in Gaia color─magnitude diagrams, which indicates that ∼6% of massive WDs are delayed in their cooling by as much as ∼10 Gyr. However, it is unclear how these stars end up with such a high concentration of 22Ne and if a significant fraction of the more common average-mass WDs go through distillation. We argue that a significant metal-rich stellar population in the solar neighborhood should lead to distilled WDs, without requiring a binary merger. We use MESA along with the carbon, nitrogen, and oxygen abundances derived from high-resolution spectroscopy of stars included in the Hypatia catalog to predict the 22Ne mass fraction in their descendant WDs. We find that 0.6%─2.5% of the WDs in the solar neighborhood have sufficient 22Ne in their interiors to go through multi-Gyr cooling delays, which could significantly inflate their numbers in the observed samples. Hence, 22Ne distillation and long-lived habitable zones around WDs should be relatively common in the solar neighborhood. We also use a Galactic model to predict the fraction of WDs that go through distillation as a function of Galactocentric distance. The fraction of distilled WDs is ∼2%─8% near the Galactic center and declines steadily toward the outer disk.

Keywords: White dwarf stars, Habitable zone, Stellar evolution
Further Evidence for a Direct-collapse Origin of the Supermassive Black Hole at the Center of the ∞ Galaxy. The z = 1.14 ∞ galaxy consists of two ringed nuclei with an active supermassive black hole (SMBH) in between them. The system is likely the result of a nearly face-on collision between two disk galaxies with massive bulges. In P. van Dokkum et al. we suggested that the SMBH may have formed from shocked and compressed gas at the collision site in a runaway gravitational collapse. Here we test this hypothesis using newly obtained James Webb Space Telescope NIRSpec integral field unit observations. We first confirm that the system has a cloud of gas in between the nuclei that is photoionized by an active galactic nucleus–like object near its center. Next, we constrain the origin of the SMBH from its radial velocity. If it formed in the cloud its velocity should be similar to the surrounding gas, whereas it would be offset if the SMBH had escaped from one of the nuclei or were associated with a faint galaxy. We find that the radial velocity of the SMBH is within ∼50 km s‑1 of that of the surrounding gas, as expected if the SMBH formed within the cloud. Unexpectedly, we find that both nuclei have active SMBHs as well, as inferred from very broad Hα emission with FWHM ∼ 3000 km s‑1. This rules out scenarios where the central SMBH was ejected from one of the nuclei in a gravitational recoil. Taken together, these results strengthen the hypothesis that the object at the center of the ∞ galaxy is a newly formed SMBH.

Keywords: Astrophysical black holes
CHIME/Fast Radio Burst/Pulsar Discovery of a Nearby Long-period Radio Transient with a Timing Glitch. We present the discovery of a 421 s long period transient using the CHIME telescope, CHIME J0630+25. The source is localized to R.A. = 06:30:38.4  ±1'  decl. = 25:26:23  ±1'  using voltage data acquired with the CHIME baseband system. A timing analysis shows that a model including a glitch is preferred over a nonglitch model with dF/F = 1.3 × 10‑6, consistent with other glitching neutron stars. The timing model suggests a surface magnetic field of ∼1.5 × 1015 G and a characteristic age of ∼1.28 × 106 yr. A separate line of evidence to support a strong local magnetic field is an abnormally high rotation measure of RM = ‑347.8(6) rad m‑2 relative to CHIME J0630+25's modest dispersion measure of 22(1) pc cm‑2, implying a dense local magneto-ionic structure. As a result, we believe that CHIME J0630+25 is a magnetized, slowly spinning, isolated neutron star. This marks CHIME J0630+25 as the longest period neutron star and the second-longest period neutron star with an inferred magnetar-like field. Based on dispersion measure models and comparison with pulsars with distance measurements, CHIME J0630+25 is located at a nearby distance of 170 ‑100+310  pc (95.4%), making it an ideal candidate for follow-up studies.

Keywords: Neutron stars, Transient sources, Transient detection, Compact objects, Radio pulsars
Measuring the Magnetic Field of a Coronal Mass Ejection from the Low to Middle Corona. A major challenge in understanding the initiation and evolution of coronal mass ejections (CMEs) is measuring the magnetic field of the magnetic flux ropes (MFRs) that drive CMEs. Recent developments in radio imaging spectroscopy have paved the way for diagnosing the CMEs' magnetic field using gyrosynchrotron radiation. We present magnetic field measurements of a CME associated with an X5-class flare by combining radio imaging spectroscopy data in microwaves (1─18 GHz) and meter waves (20─88 MHz), obtained by the Owens Valley Radio Observatory's Expanded Owens Valley Solar Array (EOVSA) and Long Wavelength Array (OVRO-LWA), respectively. EOVSA observations reveal that the microwave source, observed in the low corona during the initiation phase of the eruption, outlines the bottom of the rising MFR-hosting CME bubble seen in extreme ultraviolet and expands as the bubble evolves. As the MFR erupts into the middle corona and appears as a white-light CME, its meter-wave counterpart, observed by OVRO-LWA, displays a similar morphology. For the first time, using gyrosynchrotron spectral diagnostics, we obtain magnetic field measurements of the erupting MFR in both the low and middle corona, corresponding to coronal heights of 0.02 and 1.83 R⊙. The magnetic field strength is found to be around 300 G at 0.02 R⊙ during the CME initiation and about 0.6 G near the leading edge of the CME when it propagates to 1.83 R⊙. These results provide critical new insights into the magnetic structure of the CME and its evolution during the early stages of its eruption.

Keywords: Solar coronal radio emission, Solar flares, Solar physics, Solar radio emission, Solar coronal mass ejections, Solar filament eruptions, Solar magnetic fields, Solar radio flares
Binary Stars Take What They Get: Evidence for Efficient Mass Transfer from Stripped Stars with Rapidly Rotating Companions. Binary stars and their interactions shape the formation of compact binaries, supernovae, and gravitational-wave sources. The efficiency of mass transfer—the fraction of mass retained by the accretor during binary interaction—is a critical parameter that significantly impacts the final fates of these systems. However, this parameter is observationally poorly constrained, due to the scarcity of well-characterized post-mass-transfer binaries. Be+sdOB binaries, consisting of a rapidly rotating Be star and a stripped hot subdwarf companion, are particularly valuable for studying mass transfer, since they represent clear examples of past binary interaction. Recently, a significantly expanded observational sample of 16 Be+sdOB binaries with well-constrained masses was obtained through combined spectroscopic and interferometric observations. In this work, we compile and analyze this sample, to provide robust constraints on the mass-transfer efficiency in binaries that underwent stable mass transfer during the donor's hydrogen-shell-burning phase. Our analysis reveals that the mass transfer was predominantly conservative: half of the systems require mass-transfer efficiencies above 50%. This challenges the commonly adopted assumptions of highly nonconservative mass transfer in binary evolution modeling. Our findings are inconsistent with models that account for spinup and limit accretion due to a centrifugal barrier. We also find tension with a commonly used mass-transfer model in rapid population synthesis that limits accretion based on the thermal timescale of the accretor. These results have strong implications for almost all products of binary evolution, including a variety of supernovae, white dwarfs, blue stragglers, runaway stars, X-ray binaries, and gravitational-wave sources.

Keywords: Binary stars, Subdwarf stars, Stellar evolutionary models, Roche lobe overflow, Stellar accretion, Be stars
JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e. TRAPPIST-1 e is one of the very few rocky exoplanets that is both amenable to atmospheric characterization and resides in the habitable zone of its star—located at a distance from its star such that it might, with the right atmosphere, sustain liquid water on its surface. Here, we present a set of four JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e obtained in mid-to-late 2023. Our transmission spectra exhibit similar levels of stellar contamination as observed in prior works for other planets in the TRAPPIST-1 system but over a wider wavelength range, showcasing the challenge of characterizing the TRAPPIST-1 planets even at relatively long wavelengths (3–5 μm). While we show that current stellar modeling frameworks are unable to explain the stellar contamination features in our spectra, we demonstrate that we can marginalize over those features instead using Gaussian processes, which enables us to perform novel exoplanet atmospheric inferences with our transmission spectra. In particular, we are able to rule out cloudy, primary H2-dominated (≳80% by volume) atmospheres at better than a 3σ level. Constraints on possible secondary atmospheres on TRAPPIST-1 e are presented in a companion paper. Our work showcases how JWST is breaking ground in the precision needed to constrain the atmospheric composition of habitable-zone rocky exoplanets.

Keywords: Extrasolar rocky planets, Exoplanets, Exoplanet astronomy, James Webb Space Telescope, Habitable zone, Habitable planets, Exoplanet atmospheres
JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1 e. The TRAPPIST-1 system offers one of the best opportunities to characterize temperate terrestrial planets beyond our own solar system. Within the TRAPPIST-1 system, planet e stands out as highly likely to sustain surface liquid water if it possesses an atmosphere. Recently, we reported the first JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e, revealing significant stellar contamination, which varied between the four visits. Here, we assess the range of planetary atmospheres consistent with our transmission spectrum. We explore a wide range of atmospheric scenarios via a hierarchy of forward modeling and retrievals. We do not obtain strong evidence for or against an atmosphere. Our results weakly disfavor CO2-rich atmospheres for pressures corresponding to the surface of Venus and Mars and the cloud tops of Venus at 2σ. We exclude H2-rich atmospheres containing CO2 and CH4 in agreement with past work but find that higher mean molecular weight, N2-rich atmospheres with trace CO2 and CH4 are permitted by the data. Both a bare rock and N2-rich atmospheric scenario provide adequate fits to the data but do not fully explain all features, which may be due to either uncorrected stellar contamination or atmospheric signals. Ongoing JWST observations of TRAPPIST-1 e, exploiting consecutive transits with TRAPPIST-1 b, will offer stronger constraints via a more effective stellar contamination correction. The present work is part of the JWST Telescope Scientist Team Guaranteed Time Observations, which is performing a Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS).

Keywords: James Webb Space Telescope, Habitable zone, Exoplanet atmospheres
Detection of Low-redshift Excess in Supernova-linked Gamma-Ray Bursts. Gamma-ray bursts (GRBs) are traditionally classified into long (lGRBs) and short durations based on their T90, with lGRBs widely used as tracers of the cosmic star formation rate (SFR) due to their observed association with core-collapse supernovae (SNe). However, recent detections of kilonovae accompanying some lGRBs challenge this assumption, suggesting potential contamination from compact binary mergers. Here, we move beyond the conventional T90-based classification and focus exclusively on GRBs directly associated with SNe—the most direct signatures of massive stellar collapse—to reassess their connection to the SFR. Using a sample of SN/GRBs, we construct the luminosity–redshift (L–z) plane and uncover a significant correlation between these variables. To account for observational biases, we apply the τ statistic and Lynden-Bell's C‑ method to derive the intrinsic luminosity function and formation rate. Our analysis reveals that even among this well-defined subsample, the SN/GRB formation rate still exceeds the SFR at low redshifts (z &lt; 1). These findings suggest that GRBs at low redshift may not serve as reliable tracers of the SFR, and that larger samples are required to further investigate this discrepancy.

Keywords: Luminosity function, Gamma-ray bursts, Star formation, Supernovae
The Sun Reversed Its Decades-long Weakening Trend in 2008. Over the course of two decades until 2008, the solar wind became significantly weaker with a constant declining trend in many important solar wind parameters, and solar cycle 24 being the weakest on record since the start of the space age. Here we show that since 2008, the Sun has reversed this long-term weakening trend with a steady increase in various solar wind proton parameters observed at 1 au. Furthermore, comparison of values from a fitted trend to data between 2008 and 2025 show the following increases in solar wind proton parameters: speed (~6%), density (~26%), temperature (~29%), thermal pressure (~45%), mass flux (~27%), momentum flux or dynamic pressure (~34%), energy flux (~40%), interplanetary magnetic field magnitude (~31%), and the radial component of the magnetic field (~33%). This has important implications on long-term solar trends, implying that the exceptional weakness of solar cycle 24 was most likely a recent outlier and that the Sun is not entering a modern era Maunder/Dalton-like minimum phase in its solar variation, but is instead recovering from a ~20 yr decline. Presently, the trending average solar wind dynamic pressure of ~1.9 nPa in the current solar cycle, however, is still lower than the recorded ~2.4 nPa at the end of the 20th century. Continuous future measurements will reveal whether this increase will continue in upcoming solar cycles or whether these parameters will remain stable.

Keywords: Solar cycle, The Sun, Solar activity
X-Ray Investigation of Possible Super-Eddington Accretion in a Radio-loud Quasar at z = 6.13. We present radio and X-ray observations of the recently discovered z = 6.13 radio-powerful quasar RACS J032021.44‑352104.1 using the upgraded Giant Metrewave Radio Telescope, the Australia Telescope Compact Array, the Australian Large Baseline Array, and Chandra. The observed radio properties are in line with what is typically observed in high-z radio quasars (αr = 0.72 ± 0.02 and L1.4 GHz = 5.8 ± 0.9 × 1026 W Hz‑1). Despite the relatively low X-ray flux observed, F0.5‑7.0 keV = 2.3 ± 0.5 × 10‑14 erg s‑1 cm‑2, the intrinsic luminosity in the 2–10 keV rest frame is markedly high,  L2-10keV=1.8‑0.7+1.1×1046  erg s‑1, making RACS J032021.44‑352104.1 one of the most luminous quasars currently known at z &gt; 5.5. The high X-ray luminosity is largely driven by an extrapolation to energies below the observable X-ray window with Chandra and the slope derived in the 0.5–7 keV band (or 3.5–50 keV in the rest frame; ΓX = 3.3 ± 0.4). By analyzing the overall spectral energy distribution of the quasar, we found that the remarkably soft X-ray emission (1) cannot be produced by relativistic jets, even when relativistic boosting is considered, and (2) is consistent with expectations for a super-Eddington accreting supermassive black hole. If such a high accretion rate was confirmed, this source would be a unique laboratory to study high accretion in the early Universe and could help resolve some challenges inherent in early black hole growth paradigms.

Keywords: X-ray astronomy, Supermassive black holes, Jets, High energy astrophysics, Quasars, Relativistic jets, Radio loud quasars, Active galactic nuclei, Galaxy accretion
Optical Spectroscopy of the Most Compact Accreting Binary Harboring a Magnetic White Dwarf and a Hydrogen-rich Donor. Accreting white dwarfs (WDs) in close binary systems, commonly known as cataclysmic variables (CVs), with orbital periods below the canonical period minimum (≈80 minutes) are rare. Such short periods can only be reached if the donor star in the CV is either significantly evolved before initiating mass transfer to the WD or is metal-poor. We present optical photometry and spectroscopy of Gaia19bxc, a high-amplitude variable identified as a polar CV with an exceptionally short orbital period of 64.42 minutes—well below the canonical CV period minimum. High-speed photometry confirms persistent double-peaked variability consistent with cyclotron beaming, thus indicating the presence of a magnetic WD. Phase-resolved Keck/Low-Resolution Imaging Spectrometer (LRIS) spectroscopy reveals strong hydrogen and helium emission lines but no donor features, indicating the accretor is a magnetic WD and the donor is hydrogen-rich, but cold and faint. The absence of a detectable donor and the low inferred temperature (≲3500 K) disfavor an evolved donor scenario. Instead, the short period and the system's halo-like kinematics suggest Gaia19bxc may be the first known metal-poor polar. Because metal-poor donors are more compact than solar-metallicity donors of the same mass, they can reach shorter minimum periods. Gaia19bxc is one of only a handful of known metal-poor CVs below the canonical period minimum and has the shortest period of any such magnetic system discovered to date.

Keywords: White dwarf stars, Cataclysmic variable stars, Binary stars
Euclid and Roman with JWST Could Reveal Supermassive Black Holes at up to z ∼ 15. Although supermassive black holes (SMBHs) are found at the centers of most galaxies today, over 300 have now been discovered at z &gt; 6, including UHZ1 at z = 10.1 and GHZ9 at z = 10.4. They are thought to form when 104 to 105 M⊙ primordial stars die as direct-collapse black holes (DCBHs) at z ∼ 20–25. While studies have shown that DCBHs should be visible at birth at z ≳ 20 in the near-infrared (NIR) to the James Webb Space Telescope (JWST), none have considered SMBH detections at later stages of growth down to z ∼ 6–7. Here, we present continuum NIR luminosities for a black hole (BH) like ULAS J1120+0641, a 1.35 × 109 M⊙ quasar at z = 7.1, from a cosmological simulation for Euclid, Roman Space Telescope (RST), and JWST bands from z = 6 to 15. We find that Euclid and RST could detect such BHs, including others like UHZ1 and GHZ9, at much earlier stages of evolution, out to z ∼ 14–15, and that their redshifts could be confirmed spectroscopically with JWST. Synergies between these three telescopes could thus reveal the numbers of SMBHs at much higher redshifts and discriminate between their evolution pathways because Euclid and RST can capture large numbers of them in wide-field surveys for further study by JWST.

Keywords: Supermassive black holes, Quasars
The Link between Athor and EL Meteorites Does Not Constrain the Timing of the Giant Planet Instability. The asteroid Athor, residing today in the inner main asteroid belt, has been recently identified as the source of EL enstatite meteorites to Earth. It has been argued that Athor formed in the terrestrial region—as indicated by a similarity in isotopic compositions between Earth and EL meteorites—and was implanted in the belt ≳60 Myr after the formation of the solar system. A recently published study modeling Athor's implantation in the belt further concluded, using an idealized set of numerical simulations, that Athor could not have been scattered from the terrestrial region and implanted at its current location unless the giant planet dynamical instability occurred after Athor's implantation (≳60 Myr). In this work, we revisit this problem with a comprehensive suite of dynamical simulations of the implantation of asteroids into the belt during the terrestrial planet accretion. We find that Athor-like objects can in fact be implanted into the belt long after the giant planets' dynamical instability. The probability of implanting Athor analogs when the instability occurs at ≲15 Myr is at most a factor of ∼2 lower than that of an instability occurring ∼100 Myr after the solar system formation. Moreover, Athor's implantation can occur up to ≳100 Myr after the giant planet instability. We conclude that Athor's link to EL meteorites does not constrain the timing of the solar system's dynamical instability.

Keywords: Solar system, Solar system gas giant planets, Solar system terrestrial planets, Asteroid belt, Dynamical evolution