Sazuna/UAT_keywords huggingface dataset:
Memoirs of Mass Accretion: Probing the Edges of Intracluster Light in Simulated Galaxy Clusters. The diffuse starlight extending throughout massive galaxy clusters, known as intracluster light (ICL), has the potential to be read as a memoir of mass accretion: informative, individual, and yet imperfect. Here, we combine dark-matter-only zoom-in simulations from the Symphony suite with the NIMBUS "star-tagging" model of the stellar halo to assess how much information about the mass assembly of an individual galaxy cluster can be gleaned from idealized measurements of ICL outskirts. We show that the edges of a cluster's stellar profile—the primary (Rsp⋆,1) and secondary (Rsp⋆,2) stellar "splashback" radii—are sensitive to both continuous mass accretion histories (MAHs) and discrete merger events, making them potentially powerful probes of a cluster's past. We find that Rsp⋆,1 strongly correlates with the cluster's mass ∼1 dynamical time ago, while Rsp⋆,2 traces more recent MAH to a slightly lesser degree. In combination, these features can further distinguish between clusters that have and have not undergone a major merger within the past dynamical time. We use both to predict realistic cluster MAHs with the MULTICAM framework. These outer ICL features are significantly more sensitive to mass accretion and merger histories than the stellar mass gap and halo concentration, and perform comparably to the commonly used X-ray-based tracer of relaxedness, xoff. While our analysis is idealized, the relevant ICL features are potentially detectable in next-generation deep imaging of nearby clusters. This work highlights the promise of ICL measurements and lays the groundwork for more detailed forecasts of their power.

Keywords: Galaxy clusters, Galaxy formation, Galaxy stellar halos, Dark matter
Magnetic Field-line Curvature and Its Role in Particle Acceleration by Magnetically Dominated Turbulence. We employ first-principles, fully kinetic particle-in-cell simulations to investigate magnetic field-line curvature in magnetically dominated turbulent plasmas and its role in particle acceleration through curvature-drift motion along the motional electric field. By varying the fluctuation-to-mean-magnetic-field ratio δB0/B0, we examine curvature κ statistics and their connection to particle acceleration. The curvature probability densities display broad power-law wings, scaling linearly in κ below the peak and developing hard high-κ tails for δB0/B0 ≳ 1. As the mean field strengthens, the high-κ tails steepen, and large-curvature events are suppressed when δB0/B0 ≪ 1. The probability density functions of magnetic field-line contraction, vE · κ, with vE the field-line velocity, develop power-law tails well described by a symmetric Pareto distribution, characteristic of stochastic and intermittent energy exchanges, with the tails becoming harder as δB0/B0 increases. Our guiding-center analysis shows that curvature-drift acceleration accounts for a substantial fraction of the energization via the motional electric field, and that it strengthens with increasing δB0/B0. For well-magnetized particles, curvature-drift acceleration typically exceeds ∇B drift, polarization drift, and betatron contributions. These results identify curvature-drift acceleration as a principal pathway through which magnetized turbulence transfers energy to nonthermal particles in astrophysical plasmas.

Keywords: Plasma physics, Plasma astrophysics, High energy astrophysics, Cosmic rays
Colors of Life in the Clouds: Biopigments of Atmospheric Microorganisms as a New Signature to Detect Life on Planets like Earth. When Carl Sagan and Ed Salpeter envisioned potential sinkers, floaters, and hunters living in Jupiter's clouds in 1976, the nature of life in Earth's atmosphere remained widely unknown. Decades later, research has revealed a remarkable variety of microorganisms in our atmosphere. However, the spectral features of airborne microbes as biomarkers for detecting atmospheric life remained a mystery. Here, we present the first reflectance spectra of biopigments of atmospheric microorganisms based on laboratory cultivars of seven microbial strains isolated from Earth's atmosphere. We show their distinct UV-resistant biosignatures and their impacts on models of diverse planetary scenarios, using Habitable Worlds Observatory parameters. The reflectance of these biopigments from aerial bacteria creates the means to detect them on other Earth-like planets. It provides a paradigm shift that moves the search for life beyond the surface of a planet to ecosystems in atmospheres and clouds.

Keywords: Biosignatures, Exoplanets, Exoplanet surface variability
Preperihelion Development of Interstellar Comet 3I/ATLAS. We describe preperihelion optical observations of interstellar comet 3I/ATLAS taken during 2025 July─September using the Nordic Optical Telescope. Fixed aperture photometry of the comet is well described by a power-law function of heliocentric distance, rH, with the exponent ("index") n = 3.8 ± 0.3 across the 4.6─1.8 au distance range (phase function 0.04 ± 0.02 mag degree−1 assumed). This indicates that the dust production rates vary in proportion to  rH−1.8±0.3 . An  rH−2  variation is expected of a strongly volatile material, and consistent with independent spectroscopic observations showing that carbon dioxide is the primary driver of activity. The measured heliocentric index is unremarkable in the context of solar system comets, for which n is widely dispersed, and provides no basis on which to describe 3I as either dynamically old (thermally processed) or new (pristine). The morphology of the comet changes from a Sun-facing dust fan in the early 2025 July observations, to one dominated by an antisolar dust tail at later dates. We attribute the delayed emergence of the tail to the large size (effective radius 100 μm) and slow ejection (5 m s−1) of the optically dominant dust particles, and their consequently sluggish response to solar radiation pressure. Small (micron-sized) particles may be present but not in numbers sufficient to dominate the scattering cross section. Their relative depletion possibly reflects interparticle cohesion, which binds small particles more effectively than large ones. A similar preponderance of 100 μm grains was reported in 2I/Borisov. However, 2I differed from 3I in having a much smaller (asteroid-like) heliocentric index, n = 1.9 ± 0.1. Dust production rates in 3I are ∼180 kg s−1 at 2 au, compared with ∼70 kg s−1 in 2I/Borisov at the same distance.

Keywords: Asteroids, Long period comets, Interstellar objects, Comets, Exocomets
JWST-TST DREAMS: The Nightside Emission and Chemistry of WASP-17b. Theoretical studies have suggested using planetary infrared excess (PIE) to detect and characterize the thermal emission of transiting and nontransiting exoplanets, although the PIE technique requires empirical validation. Here, we apply the PIE technique to a combination of JWST NIRSpec G395H transit and eclipse measurements of WASP-17b, a hot Jupiter orbiting an F-type star, obtained consecutively (one-half of the orbital period or 1.8 days apart) as part of the JWST-TST program to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy. Using the in-eclipse measured stellar spectrum to circumvent the need for ultraprecise stellar models, we extract the first JWST nightside emission spectrum of WASP-17b using only transit and eclipse data, thereby performing a controlled test of the PIE technique. From the WASP-17b nightside spectrum, we measure a nightside equilibrium temperature of 1006 ± 276 K and find tentative evidence for nightside SO2 absorption ( lnB=1.4 ). In context with the dayside, the temperature of the nightside is consistent with: (1) previous eclipse mapping findings that suggest relatively inefficient day─night heat transport; and (2) a nonzero bond albedo of  0.42−0.10+0.06 . SO2 on the nightside, if confirmed, would represent the first direct evidence for transport-induced chemistry, matching previous model predictions and opening a new door onto the 3D nature of giant exoplanets. Our results suggest that PIE is feasible with JWST/NIRSpec for two epochs separated in time by significantly less than the rotation period of the host star.

Keywords: Exoplanet atmospheric composition , Hot Jupiters, Exoplanets, Exoplanet astronomy, James Webb Space Telescope, Extrasolar gaseous planets, Exoplanet atmospheres
Neural Enhancement of the Traditional Wang─Sheeley─Arge Solar Wind Relation. The Wang─Sheeley─Arge (WSA) model has been the cornerstone of operational solar wind forecasting for nearly two decades, owing to its simplicity and physics-based formalism. However, its performance is strongly dependent on several empirical parameters that are typically fixed or tuned manually, limiting its adaptability across varying solar conditions. In this study, we present a neural enhancement to the WSA framework (referred to as WSA+) that systematically optimizes the empirical parameters of the WSA solar wind speed relation using in situ observations within a differentiable physics-constrained pipeline. The approach operates in two stages: first, a neural optimizer adjusts WSA parameters independently for each Carrington rotation to better match the observed solar wind data. Then, a neural network learns to predict these optimized speed maps directly from magnetogram-derived features. This enables generalization of the optimization process and allows inference for new solar conditions without manual tuning. WSA+ preserves the interpretability of the original relation while significantly improving the match with OMNI in situ data across multiple performance metrics, including correlation and error statistics. It consistently outperforms the traditional WSA relation across both low and high solar activity periods, with average improvements of approximately 40%. By integrating data-driven learning with physical constraints, WSA+ offers a robust and adaptable enhancement, with immediate utility as a drop-in replacement in global heliospheric modeling pipelines.

Keywords: Heliosphere, Space weather, Solar wind, Magnetogram, Solar coronal holes
A Deep Dive down the Broad-line Region: Permitted O I, Ca II, and Fe II Emission in an Active Galactic Nucleus Little Red Dot at z = 5.3. We present a spectroscopic analysis of a broad-line active galactic nucleus (AGN) selected as a little red dot (LRD) at z = 5.3 behind the Bullet cluster (Bz5.3) based on JWST/NIRCam and NIRSpec data. The detection of strong Fe II, O I, and Ca II triplet emission lines, along with the evidence of broad Balmer lines, provides strong evidence of a broad-line region (BLR) and an accreting supermassive black hole. Notably, we report the first detection of the λ1304 bump (i.e., a blend of O I λ1304 and Si II) at high redshift, a feature commonly seen in local AGNs but not yet reported in the early Universe. The O I λ1304/λ8446 photon ratio provides an independent measurement of dust attenuation in galaxies. In Bz5.3, this ratio is highly suppressed (0.1─0.3), implying significant internal dust extinction, with estimated dust attenuation AV ∼ 0.4─1.0. We identify Lyβ fluorescence as the dominant excitation mechanism of the low-ionization lines, with additional contributions from collisional excitation. High O I λ8446 equivalent width and weak O I λ7774 support this interpretation. The detection of iron emission, whether from broad permitted or narrow forbidden lines, supports the presence of a stratified BLR, as also recently proposed in local LRDs. Photoionization modeling of O I λ8446 and Ca II further suggests the coexistence of multiple gas phases with distinct densities and ionization states, highlighting the complexity of the BLR. Bz5.3 thus offers a rare window into early AGN activity and BLR physics at early times.

Keywords: AGN host galaxies, Galaxy spectroscopy, Astrophysical black holes
Ultra-High-energy Cosmic Ray Production in Binary Neutron Star Mergers. Having previously argued that binary neutron star (BNS) mergers are the principle source of ultra-high-energy cosmic rays (UHECRs), we exploit here the highly constrained initial conditions to make quantitative predictions for the cutoff energy of various nuclei. UHECRs heavier than helium are accelerated in the magnetized turbulent outflow outside the jets to a rigidity  Rcut≡Ecut/eZ≍6−9  EV, consistent with the measured value  Rcut=6.3−2.3+6.3 EV from fitting data. This agreement strengthens the case that BNS mergers are the main site of UHECR production. The jets may accelerate protons and/or helium to cutoff energies ≍11.5 and ≍35 EeV, respectively. Such a jet component and its spallation products could explain the indication of a secondary light population at higher energy found in the analysis of M. S. Muzio et al. The relative abundances of different elements and the total energy in UHECRs per merger event will become calculable, pending advances in our understanding of the mechanism of ion uptake into the acceleration process and input from nuclear physics experiments. This scenario implies that each neutrino above 1 PeV is codirectional with a gravitational wave arriving ≍1 day earlier and that the highest-energy UHECRs have masses heavier than iron.

Keywords: Neutron stars, High energy astrophysics, Stellar mergers, Neutrino astronomy, Plasma astrophysics, Gravitational waves, Astrophysical processes, Particle astrophysics, Ultra-high-energy cosmic radiation, Cosmic rays
Enabling Early Transient Discovery in LSST via Difference Imaging with DECam. We present SLIDE, a pipeline that enables transient discovery in data from the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), using archival images from the Dark Energy Camera as templates for difference imaging. We apply this pipeline to the recently released Data Preview 1 (DP1; the first public release of Rubin commissioning data) and search for transients in the resulting difference images. The image subtraction, photometry extraction, and transient detection are all performed on the Rubin Science Platform. We demonstrate that SLIDE effectively extracts clean photometry by circumventing poor or missing LSST templates. We identified 29 previously unreported transients, 12 of which would not have been detected based on the DP1 DiaObject catalog. SLIDE will be especially useful for transient analysis in the early years of LSST, when template coverage will be largely incomplete or when templates may be contaminated by transients present at the time of acquisition. We present multiband light curves for a sample of known transients, along with new transient candidates identified through our search. Finally, we discuss the prospects of applying this pipeline during the main LSST survey. Our pipeline is broadly applicable and will support studies of all transients with slowly evolving phases.

Keywords: Transient detection, Supernovae, Core-collapse supernovae
Detection of Compton Scattering in the Jet of 3C 84. 3C 84 is the brightest cluster galaxy in the Perseus Cluster. It is among the closest radio-loud active galaxies and among the very few that can be detected from low-frequency radio up to TeV γ-rays. Here we report on the first X-ray polarization observation of 3C 84 with the Imaging X-ray Polarimetry Explorer, for a total of 2.2 Ms coinciding with a flare in γ-rays. This is the longest observation for a radio-loud active galaxy, which allowed us to reach unprecedented sensitivity, leading to the detection of an X-ray polarization degree of ΠX = 4.2% ± 1.3% (∼3.2σ confidence) at an X-ray electric vector polarization angle of ψX = 163° ± 9°, which is aligned with the radio jet direction on the sky. Optical polarization observations show fast variability about the jet axis as well. Our results strongly favor models in which X-rays are produced by Compton scattering from relativistic electrons—specifically synchrotron self-Compton—that takes place downstream, away from the supermassive black hole.

Keywords: Black hole physics, Jets, Relativistic jets, Radio active galactic nuclei, Brightest cluster galaxies, Polarimetry, Perseus Cluster
XRISM/Resolve Spectroscopy of the Central Engine in the Seyfert-1 AGN Mrk 279. High-resolution X-ray spectroscopy with XRISM gives an unprecedented view of the "central engine" in active galactic nuclei (AGN), providing unique insights into black hole accretion and feedback. We present an analysis of the first XRISM/Resolve spectrum of the Seyfert-1 galaxy Mrk 279, known for its complex line profiles and variability. The data reveal velocity components within the Fe Kα emission line that can be associated with the inner face of the molecular torus (r ≥ 104GM/c2), the broad-line region (BLR;  r=1650−1480+5780GM/c2 ), and the inner accretion disk ( r=81−75+280GM/c2 ). We find evidence of low-velocity, highly ionized gas that contributes an H-like Fe XXVI emission line at 6.97 keV, confirming suggestions from prior low-resolution spectra. The data do not show slow winds in absorption, but two pairs of lines—consistent with He-like and H-like Fe shifted by v ≃ 0.22c and v ≃ 0.33c—improve the fit and could represent an ultrafast outflow (UFO). Their addition to the model only reduces the Akaike information criterion by 3.6 and 3.5, respectively, signaling modest support. Additional observations are needed to definitively test for the presence of fast X-ray winds in Mrk 279. We discuss these results in the context of the geometry of the central engine in AGN, emerging trends in XRISM studies of AGN, and the nature of the potential UFOs.

Keywords: Accretion, Black hole physics, X-ray active galactic nuclei, Astrophysical black holes
1000─10,000 M<SUB>⊙</SUB> Primordial Stars Created the Nitrogen Excess in GS 3073 at z = 5.55. The advent of the James Webb Space Telescope has revealed a wealth of new galaxies just a few hundred Myr after the Big Bang, a few of which exhibit unusual N/O ratios that are difficult to explain with stellar populations today. While Wolf─Rayet stars in multiple-burst populations, very massive or rapidly rotating primordial stars, general relativistic explosions of metal-enriched supermassive stars, or the precursors of globular clusters can in principle account for the N excess in the galaxies GN-z11 and CEERS 1019, no known stars or supernovae can explain the far higher N/O ratio of 0.46 in GS 3073 at redshift z = 5.55. Here we show that the extreme N abundances in GS 3073 can be produced by 1000─10,000 M⊙ primordial (Pop III) stars. We find that these are the only candidates that can account for its large N/O ratios and its C/O and Ne/O ratios. GS 3073 is thus the first conclusive evidence in the fossil abundance record of the existence of supermassive Pop III stars at cosmic dawn.

Keywords: Early universe, Black holes, Galaxy chemical evolution, Massive stars, Chemical enrichment, Galaxy evolution
The Near-ultraviolet Spectra of FU Orionis Accretion Disks. We present the results of the first high-sensitivity near-ultraviolet (NUV; 1800─3200 Å) survey of FU Ori objects, using the Hubble Space Telescope STIS spectrograph. We compare new low-resolution spectra for six sources with predictions from accretion disk models and find that all show emission in excess of the disk model spectrum. The physical properties of the NUV emission excess are very consistent among the sample, with a mean luminosity of 10−1.11±0.4 L⊙ and temperature of 16,400 ± 2600 K—despite spanning 0.9 dex in M*, 1.3 dex in  Ṁ , and 0.7 dex in Lacc. We use the spectra to conclusively rule out the existence of a hot boundary layer in FU Ori accretion disks. We then discuss the source of the excess emission in the context of recent simulations of FU Ori outbursts and boundary layer accretion. The UV spectra also show the often-seen C II] 2326 Å multiplet and Mg II 2796/2803 Å doublet, as well as the unusual Fe II] 2507/2509 Å doublet, a feature that is not seen in the existing UV spectra of other young stellar objects. We measure and compare the luminosities of these lines in outbursting with those in nonoutbursting objects.

Keywords: Optical bursts, Near ultraviolet astronomy, FU Orionis stars, Ultraviolet spectroscopy, Star formation, Stellar accretion disks
XRISM/Resolve Reveals the Complex Iron Structure of NGC 7213: Evidence for Radial Stratification between Inner Disk and Broad-line Region. We present the first high-resolution X-ray spectrum of NGC 7213 obtained with XRISM/Resolve, supported by simultaneous XMM-Newton, NuSTAR, and SOAR optical data. The XRISM spectrum resolves the neutral Fe Kα into two components: a narrow core ( FWHM=650−220+240kms−1 ), consistent with emission at the dust sublimation radius, and a broader asymmetric line, best described by disklike emission from ∼100 Rg. This disk component mirrors the profile of the double-peaked Hα line observed in the optical. In addition, we detect broadened Fe XXV and Fe XXVI emission lines, whose inferred locations bridge the gap between the inner disk and the optical broad-line region. The weak narrow Fe Kα equivalent width (EW = 32 ± 6 eV) and the absence of a Compton hump imply a low-covering-fraction, Compton-thin torus. Together, these results reveal a radially stratified structure in NGC 7213, spanning nearly 4 orders of magnitude in radius, and place the source in an intermediate-accretion state (λEdd = 0.1%─1%), where the inner disk and broad-line region remain, while the torus shows signs of dissipation.

Keywords: Low-luminosity active galactic nuclei, Active galactic nuclei, Black holes, X-ray active galactic nuclei
A Panchromatic View of Late-time Shock Power in the Type II Supernova 2023ixf. We present multiwavelength observations of the Type II supernova (SN II) 2023ixf during its first 2 yr of evolution. We combine ground-based optical/near-infrared spectroscopy with Hubble Space Telescope far- and near-ultraviolet spectroscopy and James Webb Space Telescope near- and mid-infrared photometry and spectroscopy to create spectral energy distributions of SN 2023ixf at +374 and +620 days postexplosion, covering a wavelength range of ∼0.1─30 μm. The multiband light curve of SN 2023ixf follows a standard radioactive decay decline rate after the plateau until ∼500 days, at which point shock-powered emission from ongoing interaction between the SN ejecta and circumstellar material (CSM) begins to dominate. This evolution is temporally consistent with 0.3─10 keV X-ray detections of SN 2023ixf and broad "boxy" spectral line emission, which we interpret to signal reprocessing of shock luminosity in a cold dense shell located between forward and reverse shocks. Using the expected absorbed radioactive decay power and the detected X-ray luminosity, we quantify the total shock-powered emission at the +374 and +620 day epochs and find that it can be explained by nearly complete thermalization of the reverse shock luminosity as SN 2023ixf interacts with a continuous, "wind-like" CSM with a progenitor mass-loss rate of  Ṁ≍10−4  M⊙ yr−1 (vw = 20 ± 5 km s−1). Additionally, we construct multiepoch spectral models from the non-LTE radiative transfer code CMFGEN that contain radioactive decay and shock powers as well as dust absorption, scattering, and emission. We find that models with shock powers of Lsh = (0.5─1) × 1040 erg s−1 and ∼(0.5─1) × 10−3 M⊙ of silicate dust in the cold dense shell and/or inner SN ejecta can effectively reproduce the global properties of the late-time (&gt;300 days) UV-to-IR spectra of SN 2023ixf.

Keywords: Type II supernovae, Shocks, Radiative transfer simulations, Circumstellar matter