Sazuna/UAT_keywords huggingface dataset:
Optimizing Kilonova Searches: A Case Study of the Type IIb SN 2025ulz in the Localization Volume of the Low-significance Gravitational Wave Event S250818k. Kilonovae, the ultraviolet/optical/infrared counterparts to binary neutron star mergers, are an exceptionally rare class of transients. Optical follow-up campaigns are plagued by contaminating transients, which may mimic kilonovae but do not receive sufficient observations to measure the full photometric evolution. In this work, we present an analysis of the multiwavelength dataset of supernova (SN) 2025ulz, a proposed kilonova candidate following the low-significance detection of gravitational waves originating from the potential binary neutron star merger S250818k. Despite an early rapid decline in brightness, our multiwavelength observations of SN 2025ulz reveal that it is a type IIb SN. As part of this analysis, we demonstrate the capabilities of a novel quantitative scoring algorithm to determine the likelihood that a transient candidate is a kilonova, based primarily on its three-dimensional location and light-curve evolution. We also apply our scoring algorithm to other transient candidates in the localization volume of S250818k and find that, at all times after the discovery of SN 2025ulz, there are ≥4 candidates with a score comparable to SN 2025ulz, indicating that the kilonova search may have benefited from the additional follow-up of other candidates. During future kilonova searches, this type of scoring algorithm will be useful to rule out contaminating transients in real time, optimizing the use of valuable telescope resources.

Keywords: Core-collapse supernovae, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Time domain astronomy, Supernovae
Optical/Infrared Observations of the Extraordinary GRB 250702B: A Highly Obscured Afterglow in a Massive Galaxy Consistent with Multiple Possible Progenitors. GRB 250702B was the longest gamma-ray burst ever detected, with a duration that challenges standard collapsar models and suggests an exotic progenitor. We collected a rich set of optical and infrared follow-up observations of its rapidly fading afterglow using a suite of telescopes including the W. M. Keck Observatory, the Gemini telescopes, the Magellan Baade Telescope, the Victor M. Blanco 4 m telescope, and the Fraunhofer Telescope at Wendelstein Observatory. Our analysis reveals that the afterglow emission is well described by forward shock emission from a highly obscured relativistic jet. Deep photometric observations of the host galaxy reveal a massive (1010.66 M⊙), dusty, and extremely asymmetric system that is consistent with two galaxies undergoing a major merger. The galactocentric offset, host galaxy properties, and jet characteristics disfavor a jetted tidal disruption event (TDE) around a supermassive black hole but do not definitively distinguish between competing progenitor scenarios. We find that the afterglow and host are consistent with a range of progenitors, including an atypical collapsar, a merger between a helium star and a stellar-mass black hole, the disruption of a star by a stellar-mass compact object (micro-TDE), and the tidal disruption of a star by an off-nuclear intermediate-mass black hole.

Keywords: Gamma-ray bursts, Black holes, Tidal disruption, Relativistic jets, Infrared astronomy, X-ray transient sources, Time domain astronomy, Gamma-ray transient sources
Distinguishing the Origin of Eccentric Black Hole Mergers with Gravitational-wave Spin Measurements. It remains an open question whether the binary black hole (BBH) mergers observed with gravitational-wave detectors originate from the evolution of isolated massive binary stars or were dynamically driven by perturbations from the environment. Recent evidence for nonzero orbital eccentricity in a handful of events is seen as support for a nonnegligible fraction of the population experiencing external driving of the merger. However, it is unclear from which formation channel eccentric BBH mergers would originate: dense star clusters, hierarchical field triples, active galactic nuclei, or wide binaries in the galaxy could all be culprits. Here, we investigate whether the spin properties of eccentric mergers could be used to break this degeneracy. Using the fact that different formation channels are predicted to either produce eccentric mergers with mutually aligned or randomly oriented black hole spins, we investigate how many confident detections would be needed in order for the two models to be statistically distinguishable. If a few percent of BBH mergers retain measurable eccentricity in the bandwidth of ground-based detectors, we report a ∼9% chance that we could confidently distinguish both models (Bayes factor  lnB&gt;3 ) after the fifth observing run of the LIGO-Virgo-KAGRA detector network, ∼63% for LIGO A#, and ∼98% for the Einstein Telescope and Cosmic Explorer.

Keywords: Black holes, Gravitational wave sources, Gravitational wave astronomy, Active galactic nuclei, Gravitational waves, Wide binary stars, Spin-orbit resonances, Trinary stars, Eccentricity, Star clusters
Early Evidence for Isotropic Planetary Obliquities in Young Super-Jupiter Systems. This decade has seen the first measurements of extrasolar planetary obliquities, characterizing how an exoplanet's spin axis is oriented relative to its orbital axis. These measurements are enabled by combining projected rotational velocities, planetary rotation periods, and astrometric orbits for directly imaged super-Jupiters. This approach constrains both the spin axis and orbital inclination relative to the line of sight, allowing obliquity measurements for individual systems and offering new insights into their formation. To test whether these super-Jupiters form more like scaled-up planets or scaled-down stars, we develop a hierarchical Bayesian framework to infer their population-level obliquity distribution. Using a single-parameter Fisher distribution, we compare two models: a planet-like formation scenario (κ = 5) predicting moderate alignment, versus a brown-dwarf-like formation scenario (κ = 0) predicting isotropic obliquities. Based on a sample of four young super-Jupiter systems, we find early evidence favoring the isotropic case with a Bayes factor of 15, consistent with turbulent fragmentation.

Keywords: Exoplanet formation, Hierarchical models, Exoplanet systems, Astrostatistics
Self-similar Cosmic-Ray Transport in High-resolution Magnetohydrodynamic Turbulence. We study the propagation of cosmic rays (CRs) through a simulation of magnetohydrodynamic (MHD) turbulence at an unprecedented resolution of 10,2403. We drive turbulence that is subsonic and super-Alfvénic, characterized by δBrms/B0 = 2. The high resolution enables an extended inertial range such that the Alfvén scale lA, where δB(lA) ≍ B0, is well resolved. This allows us to properly capture how the cascade transitions from large amplitudes on large scales to small amplitudes on small scales. We find that sharp bends in the magnetic field are key mediators of particle transport even on small scales via resonant curvature scattering. We further find that particle scattering in the turbulence shows strong hints of self-similarity: (1) the diffusion has a weak energy dependence over almost two decades in particle energy, and (2) the particles' random walk exhibits a broad power-law distribution of collision times such that the diffusion is dominated by the rarest, long-distance excursions. Our results suggest that large-amplitude MHD turbulence can provide efficient scattering over a wide range of CR energies and may help explain many CR observations above a ∼TeV: the flattening of the B/C spectrum, the hardening of CR primary spectra, and the weak dependence of arrival anisotropy on CR energy.

Keywords: Magnetohydrodynamics, High energy astrophysics, Plasma astrophysics, Interstellar magnetic fields, Interstellar medium, Cosmic rays
Modeling Atmospheric Ion Escape from Kepler-1649 b and c over Time. Rocky planets orbiting M dwarf stars are prime targets for atmospheric characterization, yet their long-term evolution under intense stellar winds and high-energy radiation remains poorly constrained. The Kepler-1649 system, hosting two terrestrial exoplanets orbiting an M5V star, provides a valuable laboratory for studying atmospheric evolution in the extreme environments typical of M dwarf systems. In this Letter, we show that both planets could have retained atmospheres over gigayear timescales. Using a multispecies magnetohydrodynamic model, we simulate atmospheric ion escape driven by stellar winds and extreme-ultraviolet radiation from 0.8 to 4.0 Gyr. The results reveal a clear decline in total ion escape rates with stellar age, as captured by a nonparametric LOWESS regression, with O+ comprising 98.3%─99.9% of the total loss. Escape rates at 4.0 Gyr are 2 to 3 orders of magnitude lower than during early epochs. At 0.8 Gyr, planet b exhibits 3.79× higher O+ escape rates than planet c, whereas by 4.0 Gyr its O+ escape rates becomes 39.5× lower. This reversal arises from a transition to sub-magnetosonic star─planet interactions, where the fast magnetosonic Mach number, Mf, falls below unity. Despite substantial early atmospheric erosion, both planets may have retained significant atmospheres, suggesting potential long-term habitability. These findings offer predictive insight into atmospheric retention in the Kepler-1649 system and inform future JWST observations of similar M dwarf terrestrial exoplanets aimed at refining habitability assessments.

Keywords: Stellar winds, Astrobiology, Habitable planets, Exoplanet atmospheres, Magnetohydrodynamical simulations
Prediscovery TESS Observations of Interstellar Object 3I/ATLAS. 3I/ATLAS, also known as C/2025 N1 (ATLAS), is the third known macroscopic interstellar object to pass through our solar system. We report serendipitous Transiting Exoplanet Survey Satellite (TESS) observations of 3I/ATLAS taken between 2025 May 7 and 2025 June 2, 55 days prior to the discovery date (2025 July 1). We retrieve the TESS pixel data, perform a robust background correction, and use a data-driven approach to compute the object's position on the TESS detectors. We find a consistent offset between the target's observed and predicted positions, which is dominated by uncertainty in the TESS World Coordinate System rather than ephemeris errors. 3I/ATLAS is too faint to be detected in the individual 200 s TESS integrations, so we stack images to improve detectability. We perform aperture and pixel response function (PRF) photometry on the stacked images to create two light curves. Each light curve consists of 15 measurements with a signal-to-noise ratio &gt; 3, collected across two different TESS cameras during the 26 days that the object was observed. The PRF light curve, which is more robust against image noise, in the TESS bandpass shows a gradual increase in brightness from Tmag = 20.9 ± 0.29 to 19.57 ± 0.15. This is expected as 3I/ATLAS approaches the inner solar system. Its absolute magnitude decreases from HV = 14.3 ± 0.4 to 13.7 ± 0.3 and shows signs of faint activity consistent with other observations. This Letter highlights the power of using TESS for solar system science; by increasing the number of prediscovery observations, in an otherwise sparsely populated region of the light curve, the long-term behavior of 3I/ATLAS can be investigated.

Keywords: Comets, Time domain astronomy, Photometry
Where did Heavy Binaries Go? Gravitational-wave Populations Using Delaunay Triangulation with Optimized Complexity. We investigate the joint mass─redshift evolution of the binary black hole (BBH) merger rate in the latest Gravitational-Wave Transient Catalog (GWTC-4.0). We present and apply a novel nonparametric framework for modeling multidimensional, correlated distributions based on Delaunay triangulation. Crucially, the complexity of the model—namely, the number, positions, and weights of triangulation nodes—is inferred directly from the data, resulting in a highly efficient approach that requires about 1 to 2 orders of magnitude fewer parameters and significantly less calibration than current state-of-the-art methods. We find no evidence for a peak at Mtot ∼ 70 M⊙ at low redshifts (z ∼ 0.2), where it would correspond to the m1 ∼ 35 M⊙ feature reported in redshift-independent mass spectrum analyses, and we infer an increased merger rate at high redshifts (z ∼ 1) around those masses, compatible with such a peak. When related to the time-delay distribution from progenitor formation to a BBH merger, our results suggest that sources contributing to the m1 ∼ 35 M⊙ feature follow a steeper (shallower) time-delay distribution at high (low) redshifts. This hints at contributions from different formation channels—for example, dense environments and isolated binary evolution, respectively—although firm identification of specific formation pathways will require further observations and analyses.

Keywords: Gravitational wave astronomy, Gravitational waves, Gravitational wave sources
Disturbed Cold Gas in Galaxy and Structure Formation. The cold gas in the circumgalactic medium (CGM) and its interaction with galaxies remain poorly understood. Strong Mg II (λλ2796, 2803) absorptions seen in background quasar spectra reveal large reservoirs of neutral hydrogen, potentially serving as progenitors of star-forming galaxies at high redshifts. In this study, we search for galaxies in the vicinity of very strong Mg II absorbers (rest-frame equivalent width Wr &gt; 2 Å) with high kinematic velocities (&gt;500 km s−1) at 2.0 &lt; z &lt; 6.0. Observations were conducted with the Very Large Telescope/MUSE, JWST/NIRCam, and the Atacama Large Millimeter/submillimeter Array to detect Lyα and nebular emission lines and dust continuum emission. We identify two Lyα emitters associated with a strong Mg II absorber pair, separated by ∼1000 km s−1 at z ∼ 4.87, in the vicinity of quasar J1306+0356. We observe relative differences in metallicity, dust content, and ionization states in this ultralarge absorption pair system, indicating potential metal and dust transfer within the system. For another strong Mg II absorber at z = 2.5662 (Wr = 2.638 ± 0.124 Å), toward a second quasar J0305─3150, we detect a dusty star-forming galaxy at a projected distance of D = 38 kpc. This galaxy exhibits prominent He I, [S III], and Paschen γ lines, along with significant dust continuum. It has a star formation rate of ∼121 ± 33 M⊙ yr−1 and likely harbors a rotating disk. These findings tentatively suggest that cold gas at high redshifts fuels disk formation and participates in metal and dust transfer within overdense CGM regions.

Keywords: Galaxy structure, Dust continuum emission, Circumgalactic medium
Assembling GW231123 in Star Clusters through the Combination of Stellar Binary Evolution and Hierarchical Mergers. GW231123 is the most massive binary black hole (BBH) merger detected to date by the LIGO─Virgo─KAGRA collaboration. With at least one black hole (BH) in the upper mass gap and both BHs exhibiting high spins (χ1,2 ≳ 0.8), this event challenges standard isolated binary evolution models. A compelling alternative is a dynamical origin in star clusters, where stellar binaries and hierarchical mergers may both contribute to the formation of similar BBHs. In this work, we investigate the formation of GW231123-like events in different cluster environments using the B-POP semianalytic population synthesis code. We find that low-metallicity environments (Z ≲ 0.002) are ideal for producing BBH mergers similar to GW231123. In young and globular clusters, these BBHs have components formed in stellar binaries, while in nuclear clusters, there is also a significant contribution from BHs built up via hierarchical mergers. The natal spins of BHs formed in stellar binaries are crucial to finding GW231123 analogs. In particular, our models suggest that BHs from stellar binaries are likely characterized by high spins. Simulated GW231123-like systems exhibit short delay times, tdel ∼ 0.1─1 Gyr, suggesting their progenitors formed close to the inferred merger redshift ( z=0.39−0.24+0.27 ). We argue that star clusters in metal-poor dwarf galaxies or Milky Way─like galaxies are ideal nurseries, inferring an upper limit to the local merger rate of  R∼1.6×10−3−0.16  yr−1 Gpc−3 for nuclear clusters, ∼0.036─0.72 yr−1 Gpc−3 for globular clusters, and 4 × 10−4─0.041 yr−1 Gpc−3 for young clusters.

Keywords: Intermediate-mass black holes, Stellar dynamics, Gravitational waves, Astrophysical black holes, Star clusters
Stellar Obliquities of Young Systems, Atmospheres Undergoing Contraction and Escape (SOYSAUCE): A Likely Aligned Orbit for the 3 Myr Planet TIDYE-1 b. Despite the wide range of planet─star (mis)alignments in the mature population of transiting exoplanets, the small number of known young transiting planets are nearly all aligned with the rotation axes of their host stars, as determined by the sky-projected obliquity angle. The small number of young systems with measured obliquities limits statistical conclusions. Here we determine the sky-projected obliquity (λ) of the 3 Myr transiting planet with a misaligned outer protoplanetary disk, TIDYE-1 b (IRAS 04125+2902b), using the Rossiter─McLaughlin (RM) effect. Our dataset lacks a pretransit baseline and ingress, complicating a blind RM fit. Instead, we use contemporaneous spectra and photometry from a mass-measurement campaign to model the stellar activity trend across the transit and provide an external prior on the velocity baseline. We determine  ∣λ∣=11.8−5.0+5.9° . Combined with the published rotational velocity of the star, we find a true three-dimensional obliquity of  ψ=15.2−5.7+7.3° . Our result is consistent with an aligned orbit, suggesting the planet remains aligned to its star even though the outer disk is misaligned, though additional RM observations are needed to exclude the low-probability tail of misaligned (&gt;30°) scenarios present in our posterior.

Keywords: Radial velocity, Spectroscopy, Exoplanets, Planetary alignment
Simulations of Structured Upflows from Plumes and Their Connection to the Solar Wind. Small-scale transient jetlet activity and associated upflows from coronal hole plumes are potential sources of the solar wind. To elucidate the magnetic origins and driving mechanisms of such upflows, we perform three-dimensional (3D) radiative magnetohydrodynamic simulations using the MURaM code, spanning from the upper convection zone to the low corona. We synthesize Fe X 174 Å emission to capture the plume evolution comparable to observations, examining underlying plasma flows, thermal structures, and magnetic topologies. We identify a pronounced transition from cool downflows in the lower atmosphere to hot upflows in the corona at the interface between plume-rooted like-polarity flux concentrations. These upflows are threaded by a complex, filamentary network of quasi-separatrix layers (QSLs)—a topology distinct from standard interchange reconnection scenarios. The domain-averaged mass flux over a 38 minute interval ranges from 10−9 to 10−8 g cm−2 s−1, substantially exceeding observed solar-wind loss rates. Our results demonstrate that highly structured plasma outflows are channeled along strong QSLs at open─open field boundaries, providing a pathway to sustain the solar wind from coronal-hole plumes without requiring interchange reconnection triggered by opposite-polarity flux emergence.

Keywords: Solar coronal holes, Solar coronal plumes, Radiative magnetohydrodynamics, Magnetohydrodynamical simulations
The ODYSSEUS Survey. Spatial Correlation of Magnetospheric Inclinations Points to Parsec-scale Star─Cloud Connection. The properties of stars and planets are shaped by the initial conditions of their natal clouds. However, the spatial scales over which the initial conditions can exert a significant influence are not well constrained. We report the first evidence for parsec-scale spatial correlations of stellar magnetospheric inclinations (imag), observed in the Lupus low-mass star-forming region. Applying consensus clustering with a hierarchical density-based clustering algorithm, we demonstrate that the detected spatial dependencies are stable against perturbations by measurement uncertainties. The imag correlation scales are on the order of ∼3 pc, which aligns with the typical scales of the Lupus molecular cloud filaments. Our results reveal a connection between large-scale forces—in the form of expanding shells from the Upper Scorpius and Upper Centaurus─Lupus regions—and sub-au-scale system configurations. We find that Lupus has a nonuniform imag distribution and suggest that this results from the preferential elongation of protostellar cores along filamentary axes. Nonuniformity would have significant implications for exoplanet occurrence rate calculations, so future work should explore the longevity of these biases driven by the star─cloud connection.

Keywords: Interstellar filaments, Star forming regions, Molecular clouds, Classical T Tauri stars, Protoplanetary disks, Superbubbles
Sympathetic Eruption of Two Filaments and Associated Solar Coronal Jet. Combining the high-quality observations from the Solar Dynamics Observatory, the Global Oscillation Network Group, and the Chinese Hα Solar Explorer, we report a solar coronal jet triggered by the sympathetic eruption of two filaments on 2024 January 11. Initially, the western segment of an active region filament erupted. The erupting plasma propagated eastward, approximately along the filament's axis. This eruption perturbed the magnetic field of a second filament situated near its eastern footpoint, the second filament then erupted sympathetically about 1 hr later. The eruption of the second filament is a failed one, with the majority of the filament material falling back after the initial lifting. Although no GOES flare accompanied these filament eruptions, distinct brightenings were observed following each eruption. The second eruption produced a large coronal jet, which propagated along a bent trajectory with an apparent deflection angle of approximately 90°. No clear evidence of magnetic reconnection was detected at the deflection site, thus we suspect that the jet may have traveled along an S-shaped transequatorial loop and shown a curved trajectory. This event exhibits multiple phenomena: partial filament eruption, failed filament eruption, sympathetic filament eruption, jet initiation by filament eruption, and apparently deflected jet propagation. Collectively, these observations highlight the complexity and diversity of solar activity.

Keywords: Solar activity, Solar magnetic fields, Solar filament eruptions, Solar radiation