Sazuna/UAT_keywords huggingface dataset:
Spectroscopic Characterization of Interstellar Object 3I/ATLAS: Water Ice in the Coma. We present optical and near-infrared spectroscopy of the interstellar object 3I/ATLAS, obtained with Gemini-S/GMOS and NASA IRTF/SpeX on 2025 July 5 and 14. The optical spectrum shows a red slope of ∼11% per 1000 Å between 0.5 and 0.8 μm, resembling typical D-type asteroids and distinct from ultrared trans-Neptunian objects. At longer wavelengths, the near-infrared continuum flattens to ∼3% per 1000 Å between 0.9 and 1.5 μm, with a broad absorption feature near 2.0 μm indicative of water-ice grains in the coma. Spectral modeling with a mixture of 63% amorphous carbon and 37% 1 μm-sized water ice reproduces both the continuum and the 2.0 μm band, while the 1.5 μm water-ice band is not detected, likely due to limited signal-to-noise in the IRTF data and dilution by refractory material. The close agreement between the GMOS and SpeX spectra, taken 9 days apart, indicates short-term stability in the coma's optical properties. These observations demonstrate that 3I/ATLAS is an active interstellar comet containing abundant water ice, consistent with the theoretical expectation that its home planetary system had a high bulk fraction of water ice by mass.

Keywords: Interstellar objects
The Type II SN 2025pht in NGC 1637: A Red Supergiant with Carbon-rich Circumstellar Dust as the First JWST Detection of a Supernova Progenitor Star. We present follow-up imaging and spectroscopy and pre-explosion imaging of SN 2025pht located in NGC 1637 at 12 Mpc. Our spectroscopy shows that SN 2025pht is a Type II supernova (SN) with broad lines of hydrogen and with minimal line-of-sight extinction inferred from Na I D absorption. NGC 1637 was the target of several epochs of Hubble Space Telescope (HST) and James Webb Space Telescope (JWST) imaging covering the site of SN 2025pht from 31 to 0.7 yr prior to discovery. Using a follow-up HST image of SN 2025pht aligned to these data, we demonstrate that there is a credible progenitor candidate detected in multiple epochs of HST imaging and in JWST imaging from 1.3 to 8.7 μm, the first JWST counterpart to an SN and the longest-wavelength detection of an SN progenitor star. Fitting this source to red supergiant (RSG) spectral energy distributions (SEDs), we show that it is consistent with a  log(L/L⊙)=5.0  RSG heavily reddened by circumstellar dust. The JWST photometry enables strong constraints on the nature of the circumstellar medium, and we find that the SED favors graphite-rich dust as opposed to silicate-rich dust and an optical circumstellar extinction of AV = 5.3 mag. We discuss the implications of a pre-SN RSG enshrouded in carbon-rich dust and this finding for the overall population of progenitor stars to Type II SNe, as well as the future of SN progenitor star discovery with JWST.

Keywords: Type II supernovae, Massive stars
The Impact of Alfvénic Shear Flow on Magnetic Reconnection and Turbulence. Magnetic reconnection is a fundamental and omnipresent energy conversion process in plasma physics. Novel observations of fields and particles from Parker Solar Probe (PSP) have shown the absence of reconnection in a large number of current sheets in the near-Sun solar wind. Using near-Sun observations from PSP encounters 4─11 (2020 January─2022 March), we investigate whether reconnection onset might be suppressed by velocity shear. We compare estimates of the tearing mode growth rate in the presence of shear flow for time periods identified as containing reconnecting current sheets versus nonreconnecting times, finding systematically larger growth rates for reconnection periods. Upon examination of the parameters associated with reconnection onset, we find that 85% of the reconnection events are embedded in slow, non-Alfvénic wind streams. We compare with fast, slow non-Alfvénic, and slow Alfvénic streams, finding that the growth rate is suppressed in highly Alfvénic fast and slow wind, and reconnection is not seen in these wind types, as would be expected from our theoretical expressions. These wind streams have strong Alfvénic flow shear, consistent with the idea of reconnection suppression by such flows. This could help explain the frequent absence of reconnection events in the highly Alfvénic, near-Sun solar wind observed by PSP. Finally, we find a steepening of both the trace and magnitude magnetic field spectra within reconnection periods in comparison to ambient wind. We tie this to the dynamics of relatively balanced turbulence within these reconnection periods and the potential generation of compressible fluctuations.

Keywords: Slow solar wind, Solar wind, Solar magnetic reconnection
Triples as Links between Binary Black Hole Mergers, Their Electromagnetic Counterparts, and Galactic Black Holes. We propose a formation pathway linking black holes (BHs) observed in gravitational-wave (GW) mergers, wide BH–stellar systems uncovered by Gaia, and accreting low-mass X-ray binaries (LMXBs). In this scenario, a stellar-mass BH binary undergoes isolated binary evolution and merges while hosting a distant, dynamically unimportant tertiary stellar companion. The tertiary becomes relevant only after the merger, when the remnant BH receives a GW recoil kick. Depending on the kick velocity and system configuration, the outcome can be: (1) a bright electromagnetic (EM) counterpart to the GW merger; (2) an LMXB; (3) a wide BH–stellar companion system resembling the Gaia BH population; or (4) an unbound isolated BH. Modeling the three-body dynamics, we find that ∼0.02% of LIGO–Virgo–KAGRA (LVK) mergers may be followed by an EM counterpart within ∼10 days, produced by tidal disruption of the star by the BH. The flare is likely brightest in the optical–UV and lasts for days to weeks; in some cases, partial disruption causes recurring flares with a period of ∼2 months. We further estimate that this channel can produce ∼1%–10% of Gaia BH systems in the Milky Way. This scenario provides the first physically motivated link between GW sources, Gaia BHs, and some X-ray binaries, and predicts a rare but robust pathway for EM counterparts to binary BH mergers, potentially detectable in LVK's O5 run.

Keywords: Black holes, Stellar mass black holes, Gravitational wave sources, Low-mass x-ray binary stars, Gravitational waves, LIGO, Gaia
A Disk-originated 329 Day Quasiperiodic Oscillation in the Seyfert 1 Galaxy J1626+5120. The Seyfert 1 galaxy J1626+5120 is estimated to host a 108M⊙ black hole (BH) accreting at Eddington ratio  ṁEdd≈0.043 . Its long-term multiband light-curve data show flicker-like variations, but in a well-sampled g-band light curve, we are able to determine a ≃329 day quasiperiodic oscillation (QPO) at a ∼4.53σ significance. Six optical spectra were obtained for the source, three of which were taken by us. The spectra show that the variations were mainly because of flux changes blueward of 4000 Å. We also analyze X-ray and ultraviolet (UV) data obtained with the Neil Gehrels Swift Observatory (Swift), which targeted the source in the past 2 yr. X-ray and UV emissions of the source show variations correlated with optical. Time lags of four UV bands and four optical bands are determined with respect to the X-ray emission, which are consistent with a continuum reprocessing disk model. These properties point out a disk origin for the QPO, likely due to Lense–Thirring (LT) precession of the accretion flow at ∼20 gravitational radii of the BH. This QPO could be a key case linking subyear-long QPOs in jets, which have more cases reported, to LT precession.

Keywords: Active galactic nuclei, Periodic orbit
Population-dependent r-process Scatter in the Globular Cluster M15. Multiple populations, defined by correlations between light element abundances, are an almost ubiquitous property of globular clusters. On the other hand, dispersions among the heavy elements are limited to a few rare clusters. In this Letter, we present Mg, Y, Ba, La, and Eu measurements for 89 stars in M15 with errors &lt;0.4 dex from Keck/DEIMOS medium-resolution spectra. We find higher Ba, La, and Eu dispersions in the first generation of stars than in the second generation at a significance of ≥2σ. This is evidence for inhomogeneous mixing of gas during the formation of the first generation of stars, which subsequently became well mixed prior to the formation of the second generation of stars. If the r-process event that caused the abundance dispersions was born with the first population of stars, it must be an r-process site with a short delay time.

Keywords: Globular star clusters, R-process, Nucleosynthesis
A Dense Molecular Ringlike Structure in Gaseous CO Depletion Region G34.74−0.12. We report the discovery of a dense molecular ringlike structure in a dense (105 cm−3), cold (parsec-scale CO depletion at a factor of 5), and young (104 yr) star-forming region G34.74−0.12, revealed by C18O (2−1), HNC (1−0), and N2H+ (1−0) observations with the Atacama Large Millimeter/submillimeter Array. The ringlike structure is redshifted with respect to the clump, spanning from Vsys,lsr + 0.9 to Vsys,lsr + 2.9 km s−1, with a total mass of 109 M⊙. It is spatially coincident with 1.3 and 3.0 mm dust continuum emission from the cores, and several protostellar outflows. However, no free─free emission or H II region is detected in association with this structure. With a slow expansion speed indicated by the position─velocity diagram, this ring structure differs from rings previously identified in more evolved star-forming regions. Possible explanations for the ring-like structure include a relic windblown bubble produced by a deeply embedded young stellar object, a hollow cavity formed by cloud─cloud interactions, a gas ring resulting from a temperature gradient, or a line-of-sight superposition of multiple outflows or dense clouds. This discovery offers a rare observational glimpse into the earliest dynamical processes involved in massive star formation.

Keywords: Interstellar line emission, Infrared dark clouds, Star forming regions, Star formation, Interstellar medium
Sensitivity to Sub-Io-sized Exosatellite Transits in the MIRI LRS Light Curve of the Nearest Substellar Worlds. JWST's unprecedented sensitivity enables precise spectrophotometric monitoring of substellar worlds, revealing atmospheric variability driven by mechanisms operating across different pressure levels. This same precision now permits exceptionally sensitive searches for transiting exosatellites—small terrestrial companions to these worlds. Using a novel simultaneous dual-band search method to address host variability, we present a search for transiting exosatellites in an 8 hr JWST/MIRI LRS light curve of the nearby (2.0 pc) substellar binary WISE J1049─5319 AB, composed of two ∼30 MJup brown dwarfs separated by 3.5 au and viewed nearly edge-on. Although we detect no statistically significant transits, our injection/recovery tests demonstrate sensitivity to satellites as small as 0.275 R⊕ (0.96 RIo or ∼1 lunar radius), corresponding to 300 ppm transit depths, and satellite-to-host mass ratios &gt;10−6. This approach paves the way for detecting Galilean moon analogs around directly imaged brown dwarfs, free-floating planets, and wide-orbit exoplanets, dozens of which are already scheduled for JWST light-curve monitoring. In our solar system, each giant planet hosts on average 3.5 moons above this threshold, suggesting that JWST now probes a regime where such companions are expected to be abundant. The technique and sensitivities demonstrated here mark a critical step toward detecting exosatellites and ultimately enabling constraints on the occurrence rates of small terrestrial worlds orbiting 1─70 MJup hosts.

Keywords: Transit photometry, Natural satellites (Extrasolar), Brown dwarfs
Observational Evidence for Spin Alignment between Galaxy Groups and Their Central Galaxies. We present a systematic observational study of the spin alignment between galaxy groups and their central galaxies using a large spectroscopic sample from the Sloan Digital Sky Survey. Unlike previous studies based on morphology or major axis alignment, we use spin as a direct, dynamically motivated probe. To match the limitations of observational data, the group spin, central-galaxy spin, and alignment angle are defined and measured in projection on the sky plane. By applying two novel spin estimators for galaxy groups, we find strong statistical evidence for a preferential alignment, with a mean projected angle of 34 .° 17 ± 0 .° 29, significantly deviating from random expectation at 37.77σ. This alignment signal persists across a wide range of group and galaxy properties, but its strength is modulated by mass, morphology, and color. Specifically, we find that more massive groups and more massive central galaxies exhibit stronger alignment. Furthermore, elliptical central galaxies show stronger alignment than spirals, and bluer central galaxies are more strongly aligned than redder ones. Our results suggest a close dynamical link between the spin of central galaxies and their host groups, modulated by their physical properties and star formation history. These results provide new insights into the dynamical connection between central galaxies and their host dark matter halos.

Keywords: Galaxy kinematics, Galaxy groups, Astrostatistics
The First Radio-bright Off-nuclear Tidal Disruption Event AT 2024tvd Reveals the Fastest-evolving Double-peaked Radio Emission. We present the first multiepoch broadband radio and millimeter monitoring of an off-nuclear tidal disruption event (TDE) using the Very Large Array, the Atacama Large Millimeter/submillimeter Array, the Allen Telescope Array, the Arcminute Microkelvin Imager Large Array, and the Submillimeter Array. The off-nuclear TDE AT 2024tvd exhibits double-peaked radio light curves and the fastest-evolving radio emission observed from a TDE to date. With respect to the optical discovery date, the first radio flare rises faster than Fν ∼ t9 at ∆t = 88─131 days and then decays as fast as Fν ∼ t−6. The emergence of a second radio flare is observed at ∆t ≍ 194 days with an initial fast rise of Fν ∼ t18 and an optically thin decline of Fν ∼ t−12. We interpret these observations in the context of a self-absorbed and free─free absorbed synchrotron spectrum, while accounting for both synchrotron and inverse Compton cooling. We find that a single prompt outflow cannot easily explain these observations and that it is likely that either there is only one outflow that was launched at ∆t ∼ 80 days or there are two distinct outflows, with the second launched at ∆t ∼ 170─190 days. The nature of these outflows, whether sub-, mildly, or ultrarelativistic, is still unclear, and we explore these different scenarios. Finally, we find a temporal coincidence between the launch time of the first radio-emitting outflow and the onset of a power-law component in the X-ray spectrum, attributed to inverse Compton scattering of thermal photons.

Keywords: Supermassive black holes, Tidal disruption, Radio astronomy, Time domain astronomy
The Rings of (2060) Chiron: Evidence of an Evolving System. The centaur (2060) Chiron has long been a candidate for hosting material in orbit, based on occultation and photometric and spectroscopic data. Here, we present a multichord stellar occultation observed on 2023 September 10 UT that reveals new and complex structures surrounding Chiron. High-cadence light curves show multiple secondary events that are best explained (when compared with a multishell interpretation) with a system of three confined rings located at average radii of 273, 325, and 438 km, the outermost of which lies beyond Chiron's Roche limit. The rings appear coplanar, with a mean pole orientation of λ = 151∘ ± 4∘ and β = 20∘ ± 6∘. A broader, disklike structure extends from about 200 to 800 km, and a newly detected faint feature is observed at ∼1380 km. Chiron thus appears as the fourth small solar system body known for hosting a ring system. Comparisons with previous occultation events that have occurred since 1994 show that these features are not permanent. With these observations, we may witness for the first time the ongoing formation and evolution of a ring system.

Keywords: Stellar occultation, Planetary rings, Centaur group
Neural Networks as Surrogate Solvers for Time-dependent Accretion Disk Dynamics. Accretion disks are ubiquitous in astrophysics, appearing in diverse environments from planet-forming systems to X-ray binaries and active galactic nuclei. Traditionally, modeling their dynamics requires computationally intensive (magneto)hydrodynamic simulations. Recently, physics-informed neural networks (PINNs) have emerged as a promising alternative. This approach trains neural networks directly on physical laws without requiring data. We for the first time demonstrate PINNs for solving the two-dimensional, time-dependent hydrodynamics of non-self-gravitating accretion disks. Our models provide solutions at arbitrary times and locations within the training domain, and successfully reproduce key physical phenomena, including the excitation and propagation of spiral density waves and gap formation from disk─companion interactions. Notably, the boundary-free approach enabled by PINNs naturally eliminates the spurious wave reflections at disk edges, which are challenging to suppress in numerical simulations. These results highlight how advanced machine learning techniques can enable physics-driven, data-free modeling of complex astrophysical systems, potentially offering an alternative to traditional numerical simulations in the future.

Keywords: Hydrodynamical simulations, Hydrodynamics, Neural networks, Computational methods, Protoplanetary disks, Stellar accretion disks, Astrophysical fluid dynamics
Tidal Disruption Event Demographics in Supermassive Black Hole Binaries over Cosmic Times. Tidal disruption events (TDEs) offer a unique probe of supermassive black hole (SMBH) demographics, but their observed rates remain difficult to reconcile with standard single-SMBH models. In this work, we use simulations of SMBH binaries, including the combined effects of eccentric Kozai─Lidov oscillations and two-body relaxation, to explore how TDE rates scale with SMBH mass and redshift. We find that binary systems exhibit increasing TDE rates with mass, in contrast to the declining trend expected for single SMBHs. These binary-driven rates match those observed in post-starburst galaxies, suggesting that a subset of TDE hosts may contain SMBH binaries. TDE light curves in some massive galaxies exhibit unexpectedly short durations, suggesting that the disrupting SMBH may be less massive than implied by host galaxy scaling relations, consistent with disruptions by the less massive black hole in a binary. By convolving our mass-dependent rates with the SMBH mass function, we predict redshift-dependent TDE rates, which we show can be used to constrain the SMBH binary fraction. Our results provide a testable framework for interpreting TDE demographics in upcoming wide-field surveys such as Legacy Survey of Space and Time and Roman.

Keywords: Astrodynamics, Supermassive black holes, Tidal disruption, Celestial mechanics, Transient detection, Astrophysical black holes
Precision Measurement of Large Shear Signals. So far, estimators of galaxy shape distortions are only carefully studied perturbatively in the case of small shear signals, mainly for weak-lensing science. However, in the neighborhood of massive foreground clusters, a large number of background galaxies can be significantly distorted. The measurement of such large shear signals could be quite nontrivial under general observing conditions, i.e., in the presence of point-spread function and noise. In this work, we propose a nonperturbative method to exactly recover large shear signals (≳0.5) under general conditions. We test the method on simulated galaxy images and find that it is accurate down to the very faint end. This new method is particularly useful for more accurate recovery of the shear distribution in the neighborhood of massive foreground clusters, thereby improving the modeling of the underlying dark matter halo properties.

Keywords: Weak gravitational lensing, Galaxy clusters, Strong gravitational lensing, Gravitational lensing shear, Dark matter
Fine Structures of Tiny Quiet Sun Jets Observed by Solar Orbiter and Big Bear Solar Observatory. We present the first joint high-resolution observations of small-scale EUV jets using Solar Orbiter (SolO)'s Extreme Ultraviolet Imager and High Resolution Imager (EUI/HRIEUV) and Hα imaging from the Visible Imaging Spectrometer installed on the 1.6 m Goode Solar Telescope at the Big Bear Solar Observatory. These jets occurred on 2022 October 29 around 19:10 UT in a quiet Sun region, and their main axis aligns with the overarching magnetic structure traced by a cluster of spicules. However, they develop a helical morphology, while the Hα spicules maintain straight, linear trajectories elsewhere. Alongside the spicules, thin, elongated red- and blueshifted Hα features appear to envelope the EUV jets, which we tentatively call sheath flows. The EUI jet moving upward at a speed of ∼110 km s−1 is joined by a strong Hα redshift at ∼20 km s−1 to form bidirectional outflows lasting ∼2 minutes. Using AI-assisted differential emission measure analysis of SolO's Full Sun Imager, we derived total energy of the EUV jet as ∼1.9 × 1026 erg with 87% in thermal energy and 13% in kinetic energy. The parameters and morphology of this small-scale EUV jet are interpreted based on a thin flux tube model that predicts Alfvénic waves driven by impulsive interchange reconnection localized as narrowly as ∼1.6 Mm with a magnetic flux of ∼5.4 × 1017 Mx, belonging to the smallest magnetic features in the quiet Sun. This detection of intricate corona─chromospheric coupling highlights the power of high-resolution imaging in unraveling the mechanisms behind small-scale solar ejections across atmospheric layers.

Keywords: Jets, Solar magnetic reconnection, Quiet sun, Alfven waves, Solar chromosphere
A Late-time View of the Progenitor Candidates of the Type II-P SN 2009ib and SN 2012ec. The progenitors of Type II-P supernovae (SNe) are generally considered to be red supergiants. SN 2009ib and SN 2012ec are two Type II-P SNe for which progenitor candidates have been identified in preexplosion images. In this work, we use new, late-time Hubble Space Telescope observations to search for the disappearance of these two candidates and confirm their nature. In the case of SN 2009ib, the late-time high-resolution imaging reveals that the progenitor candidate is in fact a blend of multiple unresolved stars. Subsequent difference imaging shows no significant change in brightness at the SN's position, even years after the explosion. These findings indicate that the flux from the previously identified source is dominated by unresolved field stars, with little to no contribution from the genuine progenitor. Taking advantage of new observational data and methods, we constrained the progenitor mass of SN 2009ib to an upper limit of ∼10 M⊙. In the case of SN 2012ec, a comparison of preexplosion and late-time images reveals that the progenitor candidate faded by about 0.6 mag in the F814W band 7 yr after the explosion, confirming the disappearance of the progenitor.

Keywords: Late stellar evolution, Core-collapse supernovae, Type II supernovae, Massive stars, Time domain astronomy, Supernovae, Stellar evolution