Sazuna/UAT_keywords huggingface dataset:
Revealing the Origins of Galactic Globular Clusters via their Mg–Al Abundances. Many Galactic globular clusters (GCs) originated in diverse host galaxies before being subsequently incorporated into the Milky Way through hierarchical galaxy assembly. Identifying their origins is crucial for revealing galaxy properties at early times. Traditional classification methods relying on dynamical properties face inherent uncertainties stemming from the evolving Galactic potential and complex merger histories. Chemically driven classification confronts a distinct obstacle: multiple populations—abundance variations in light elements of GC members. In this Letter, we identify primordial populations exhibiting lower [Al/Fe] as reliable tracers of their birth environments' chemical evolution. A clear chemical dichotomy emerges between in situ and accreted GC populations at [Fe/H] &gt; ‑1.5, particularly in the [Mg/Fe]–[Al/Fe] plane, indicating that their progenitor galaxies have experienced fundamentally different enrichment histories. While our chemically driven classification demonstrates general consistency with dynamically driven classifications, notable discrepancies emerge: NGC 288 and M4 are reclassified as in situ, and Terzan 9 as accreted. This chemically driven GC classification provides a promising application for Galactic archaeology.

Keywords: Globular star clusters, Chemical abundances, Galaxies
Polarization Ratios of Turbulent Langmuir/<inline-formula> <mml:math><mml:mi>Z</mml:mi></mml:math> </inline-formula>-mode Waves Generated by Electron Beams in Magnetized Solar Wind Plasmas. The polarization ratios F = ∣E⊥∣2/∣E∣2 of beam-generated turbulent Langmuir/ Z -mode ( LZ ) waves and electromagnetic emissions radiated at plasma frequency ωp from such sources are studied in weakly magnetized and randomly inhomogeneous plasmas. Large-scale and long-term 2D/3V particle-in-cell simulations with parameters relevant to type III solar radio bursts are performed. Statistical studies using waveforms recorded by virtual satellites are carried out to determine the distributions of polarization ratios as a function of beam and plasma parameters. This efficient method, which mimics waveform recording by spacecraft in the solar wind, leads to results consistent with observations. Moreover, plasma random density fluctuations δn turn out to be the key factor responsible for the increase in polarization ratios up to F ∼ 1. Indeed, it is demonstrated that linear mode conversion at constant frequency near ωp of  LZ  waves scattering on δn is the most efficient and fastest process to produce large polarization ratios in randomly inhomogeneous plasmas. This is due to electromagnetic slow extraordinary  Z -mode wave emission by  LZ  wave turbulence. The results provide guidance to theoretical studies and useful support to estimate the average level of density fluctuations in solar wind plasmas.

Keywords: Radio bursts, Solar wind, Solar flares, Solar electromagnetic emission
Spectral Hardening Reveals Afterglow Emergence in Long-duration Fast X-Ray Transients: A Case Study of GRB 250404A/EP250404a. The prompt emission and afterglow phases of gamma-ray bursts (GRBs) have been extensively studied, yet the transition between these two phases remains inadequately characterized due to limited multiwavelength observational coverage. Among the recent growing samples of fast X-ray transients observed by Einstein Probe (EP), a subgroup of GRBs are captured with long-duration X-ray emission, potentially containing featured evolution from prompt emission to the afterglow phase. In this Letter, we present a detailed analysis of GRB 250404A/EP250404a, a bright, fast X-ray transient detected simultaneously by EP and the Fermi Gamma-ray Burst Monitor in X-rays and gamma rays. Its continuous X-ray emission reveals a long-duration tail, accompanied by distinct spectral evolution manifested by the spectral index αX with an initial softening, followed by an evident hardening, eventually reaching a plateau at the value of ∼–2. Early optical and near-infrared observations enable broadband modeling with forward- and reverse-shock components, confirming that the X-ray hardening signals the emergence of the external-shock afterglow. From this spectral hardening, we infer that the prompt phase in soft X-rays lasted ∼300 s, which is more than 3 times longer than the gamma-ray T90. This well-tracked soft–hard–flat spectral pattern provides a clear indication of afterglow emergence from the fading prompt emission and offers a practical criterion for identifying a distinct population of GRBs among fast X-ray transients, even when the detection of the gamma-ray counterpart or obvious temporal break is absent.

Keywords: X-ray transient sources, Gamma-ray bursts, Transient sources, High energy astrophysics
Different Inhomogeneous Evolutionary Histories for Uranus and Neptune. We present updated nonadiabatic and inhomogeneous evolution models for Uranus and Neptune, employing an interior composition of methane, ammonia, water, and rocks. Following the formation trends of the gas giants, Uranus and Neptune formation models are applied, where both planets begin with layers stable to convection. Both planets are subject to convective mixing throughout their evolution. Consistent with past work on this subject, the interior heat of Uranus evolution models is preserved by the stability of an outer composition gradient at lower initial entropy, where convective mixing is inhibited over evolutionary timescales. In contrast, if Neptune's initial entropy is enough to convectively mix its envelope, it undergoes homogenization and adiabatic cooling of the outer 40% of its envelope. The subsequent release of internal energy during Neptune's evolution, driven by the convective instability of its primordial outer compositional gradient, accounts for its higher luminosity relative to Uranus. This work proposes that the observed luminosity differences between Uranus and Neptune could be explained by the convective stability of their outer envelopes. The extensive convective mixing in Neptune can lead to a higher metallicity in its outer region compared to Uranus, a feature seen in atmospheric measurements and shown in past interior models of Neptune. Due to Neptune's more pronounced cooling, our models predict favorable conditions for hydrogen–water immiscibility in its envelope.

Keywords: Neptune, Atmospheric evolution, Solar system gas giant planets, Planetary interior, Planetary structure, Uranus
Electromagnetic Signatures from Pulsar Remnants of Binary Neutron Star Mergers: Prospects for Unique Identification Using Multiwavelength Signatures. Binary neutron star (BNS) mergers can result in the formation of long-lived magnetar remnants that can enhance neutrino and electromagnetic (EM) emissions. In this work, we study the resulting multiwavelength EM emissions and the prospects of their detectability in the current and upcoming EM telescopes. We model the pulsar-wind-nebula system where the long-lived pulsar with dipolar magnetic fields of 1013‑1015 G (magnetar) spins down and is surrounded by an outward-expanding nebula and kilonova ejecta. Although at early times following the merger the EM signatures are unobservable owing to heavy attenuation, they become observable on timescales of  O(1–10)  days after the merger. We find that the survey and follow-up observations have horizon distances ≳1 Gpc for most of the wave bands and conclude that the detection prospects for such long-lived remnants in the EM channel are promising. This is of crucial importance for multimessenger observations from BNS mergers to constrain the physical parameters of the remnants. Furthermore, we highlight how observations across the EM band can uniquely identify magnetar-powered transients resulting from BNS mergers and establish concrete associations of the detected gravitational-wave signatures with such transients.

Keywords: High energy astrophysics, Stellar mergers, Transient sources, X-ray telescopes, Gamma-ray telescopes, Radio telescopes, Optical telescopes, Time domain astronomy, Magnetars, Particle astrophysics
A JWST View of the Overmassive Black Hole in NGC 4486B. We present a new stellar dynamical measurement of the supermassive black hole in the compact elliptical galaxy NGC 4486B, based on integral field spectroscopy with JWST/NIRSpec. The two-dimensional kinematic maps reveal a resolved double nucleus and a velocity dispersion peak offset from the photometric center. Utilizing two independent methods—Schwarzschild orbit-superposition and Jeans anisotropic modeling—we tightly constrain the black hole mass by fitting the full line-of-sight velocity distribution. Our axisymmetric Schwarzschild models yield a best-fit black hole mass of  MBH   =3.6‑0.7+0.7×108M⊙ , slightly lower but significantly more precise than previous estimates. However, since our models do not account for the nonequilibrium nature of the double nucleus, this value may represent a lower limit. Across all tested dynamical models, the inferred  MBH /M* ratio ranges from ∼4% to 13%, providing robust evidence for an overmassive SMBH in NGC 4486B. Combined with the galaxy's location deep within the Virgo Cluster, our results support the interpretation that NGC 4486B is the tidally stripped remnant core of a formerly massive galaxy. As the JWST/NIRSpec field of view is insufficient to constrain the dark matter halo, we incorporate archival ground-based long-slit kinematics extending to 5″. While this provides some leverage on the dark matter content, the constraints remain relatively weak. We place only an upper limit on the dark matter fraction, with  MDM / M* ≲0.5 within 1 kpc—well beyond the effective radius. The inferred black hole mass remains unchanged with or without a dark matter halo.

Keywords: Supermassive black holes, Black holes, Compact dwarf galaxies, Compact galaxies
Detailed Radial Scale Height Profile of Dust Grains as Probed by Dust Self-scattering in HL Tau. The vertical settling of dust grains in a circumstellar disk, characterized by their scale height, is a pivotal process in the formation of planets. This study offers in-depth analysis and modeling of the radial scale height profile of dust grains in the HL Tau system, leveraging high-resolution polarization observations. We resolve the inner disk's polarization, revealing a significant nearside–farside asymmetry, with the nearside being markedly brighter than the farside in polarized intensity. This asymmetry is attributed to a geometrically thick inner dust disk, suggesting a large aspect ratio of H/R ≥ 0.15, where H is the dust scale height and R is the radius. The first ring at 20 au exhibits an azimuthal contrast, with polarization enhanced along the minor axis, indicating a moderately thick dust ring with H/R ≈ 0.1. The absence of the nearside–farside asymmetry at larger scales implies a thin dust layer, with H/R &lt; 0.05. Taken together, these findings depict a disk with a turbulent inner region and a settled outer disk, requiring a variable turbulence model with α increasing from 10‑5 at 100 au to 10‑2.5 at 20 au. This research sheds light on dust settling and turbulence levels within protoplanetary disks, providing valuable insights into the mechanisms of planet formation.

Keywords: Dust continuum emission, Protoplanetary disks, Submillimeter astronomy, Interplanetary dust, Polarimetry, Interferometry
Diffuse Neutrino Signals from Dark Stars Seeding Supermassive Black Holes. Dark stars (DSs)—first stars powered by dark matter (DM) heating rather than fusion—could form in the early Universe. They can grow to ≳105M⊙ masses and collapse into seeds of supermassive black holes (SMBHs). We demonstrate that diffuse neutrino flux generated by DSs can be observable in existing experiments and have energies reaching hundreds of MeV, providing a novel window for probing SMBH progenitors. We establish first constraints on DSs as SMBH progenitors based on DM annihilations using data from Super-Kamiokande and IceCube neutrino experiments, and consistent with James Webb Space Telescope observations. Upcoming experiments such as Hyper-Kamiokande, DUNE, and JUNO will be able to explore DS properties with enhanced sensitivity.

Keywords: Supermassive black holes, Cold dark matter, Population III stars, Cosmological neutrinos
3D Fast-mode Wave Propagation from Corona to Chromosphere: Triggering Mechanism for 3D Oscillations of Filaments. Moreton waves are widely regarded as the chromospheric counterpart of extreme ultraviolet waves propagating in the corona. However, direct observational evidence confirming their simultaneous propagation across multiple atmospheric layers—from the corona through the transition region to the chromosphere—has been lacking. In this study, we present comprehensive observational evidence of a 3D fast-mode wave propagating from the corona through the transition region into the chromosphere, exhibiting a gradual deceleration. Additionally, this wave interacts with three filaments (F1, F2, and F3) along its path, inducing oscillation with multiple amplitudes: filaments F1 and F2 exhibit simultaneous horizontal and vertical large-scale oscillations (∼20 km s‑1), while filament F3 only exhibits vertical small-scale oscillation (∼4 km s‑1). Interestingly, F1 displays a similar oscillation period of about 500 s in both horizontal and vertical directions, whereas F2 shows significantly different periods in these two dimensions (1100 and 750 s), and F3 exhibits only a vertical oscillation with a period of about 450 s. Based on this kinematic behavior, we propose that their oscillations were likely triggered by compression from the flanks of the dome-shaped wave front. We further estimate the magnetic fields of the filaments. The radial (axial) magnetic fields for F1 and F2 are estimated to be 14.9 G (28.6 G) and 9.9 G (18.6 G), respectively. For F3, we estimate its radial magnetic field to be 16.6 G.

Keywords: Solar physics, Solar coronal waves, Solar filaments
The Secular Evolution of Planetary Nebula IC 418 and Its Implications for Carbon Star Formation. The rate of stellar evolution can rarely be measured in real time. The fastest evolution (excluding event-driven evolution), where stars may evolve measurably over decades, is during the post─Asymptotic Giant Branch (AGB) phase. In this Letter we provide direct evidence for such a case. A secular, linear, factor of ∼2.5 increase is found in the strength of the [O III] lines relative to Hβ over an 130 yr period in the young, well-known, low-excitation planetary nebula IC 418. The increase is caused by the rising temperature of the central star. We use photoionization models to derive a model-dependent heating rate for the central star in the range 15─42 K yr−1. These derived heating rates are very sensitive to the stellar mass, and yield a central-star mass of ∼0.560─0.583 M⊙. Initial─final mass relations based on the Miller─Bertolami models give a progenitor main-sequence mass of 1.25─1.55 M⊙. IC 418 is a carbon-rich planetary nebula and its central star, HD 35914, has evolved from an AGB carbon star. This result shows that carbon star formation at solar metallicity extends to these low masses. This is lower than commonly assumed and suggests that post-AGB evolution may be slower than recent post-AGB models predict.

Keywords: Carbon stars, Planetary nebulae nuclei, Planetary nebulae, Late stellar evolution
Flash Ionization of the Early Universe by Population III.1 Supermassive Stars. The Population III.1 theory for supermassive black hole formation predicts that a substantial fraction of the early Universe was ionized by supermassive stars at redshifts z ∼ 20–30, an era we refer to as "The Flash." This is followed by recombination to a mainly neutral state within a few tens of Myr. Here we discuss the implications of this ionization for the scattering optical depth of the cosmic microwave background (CMB), τ. We find a fiducial contribution of τPopIII.1 ∼ 0.04. Combining this with the contribution to reionization by standard galaxy populations at z ≲ 10 with τgal ≃ 0.06, yields a total of τ ≃ 0.10. As noted recently by several authors, such a value may help resolve apparent "problems" faced by ΛCDM of discrepant CMB-based measures of the Hubble constant ("Hubble tension"), as well as negative neutrino masses and dynamical dark energy that have been implied by recent baryonic acoustic oscillation results from the Dark Energy Spectroscopic Instrument. In addition, free–free emission from The Flash boosts the cosmic radio background, which could help explain the large 21 cm absorption depth reported by the Experiment to Detect the Global EoR Signature.

Keywords: Early universe, Reionization, Cosmic microwave background radiation, Population III stars
FRB 20250316A: A Brilliant and Nearby One-off Fast Radio Burst Localized to 13 pc Precision. Precise localizations of a small number of repeating fast radio bursts (FRBs) using very long baseline interferometry (VLBI) have enabled multiwavelength follow-up observations revealing diverse local environments. However, the 2%─3% of FRB sources that are observed to repeat may not be representative of the full population. Here we use the VLBI capabilities of the full CHIME Outrigger array for the first time to localize a nearby (40 Mpc), bright (kJy), and apparently one-off FRB source, FRB 20250316A, to its environment on 13 pc scales. We use optical and radio observations to place deep constraints on associated transient emission and the properties of its local environment. We place a 5σ upper limit of L9.9 GHz &lt; 2.1 × 1025 erg s−1 Hz−1 on spatially coincident radio emission, a factor of 100 lower than any known compact persistent radio source associated with an FRB. Our Keck Cosmic Webb Imager observations allow us to characterize the gas density, metallicity, nature of gas ionization, dust extinction, and star formation rate through emission line fluxes. We leverage the exceptional brightness and proximity of this source to place deep constraints on the repetition of FRB 20250316A and find that it is inconsistent with all well-studied repeaters given the nondetection of bursts at lower spectral energies. We explore the implications of a measured offset of 190 ± 20 pc from the center of the nearest star formation region in the context of progenitor channels. FRB 20250316A marks the beginning of an era of routine localizations for one-off FRBs on tens of milliarcseconds scales, enabling large-scale studies of their local environments.

Keywords: Star forming regions, Supernova remnants, Radio bursts, Transient detection, Interstellar medium, Compact objects
James Webb Space Telescope Observations of the Nearby and Precisely Localized FRB 20250316A: A Potential Near-IR Counterpart and Implications for the Progenitors of Fast Radio Bursts. We present deep James Webb Space Telescope near-infrared imaging to search for a quiescent or transient counterpart to FRB 20250316A, which was precisely localized with the CHIME Outriggers array to an area of 11 × 13 pc in the outer regions of NGC 4141 at d ≈ 40 Mpc. Our F150W2 image reveals a faint source near the center of the fast radio burst (FRB) localization region ("NIR-1"; MF150W2 ≈ ‑2.5 mag; probability of chance coincidence ≈0.36), the only source within ≈2.7σ. We find that it is too faint to be a globular cluster, a young star cluster, a red supergiant star, or a giant star near the tip of the red giant branch (RGB). It is instead consistent with a red giant near the RGB "clump" or a massive (≳20 M⊙) main-sequence star, although the latter explanation is less likely. The source is too bright to be a supernova (SN) remnant, Crab-like pulsar wind nebula, or isolated magnetar. Alternatively, NIR-1 may represent transient emission, namely a dust echo from an energetic outburst associated with the FRB, in which case we would expect it to fade in future observations. We explore the stellar population near the FRB and find that it is composed of a mix of young massive stars (∼10–100 Myr) in a nearby H II region that extends to the location of FRB 20250316A and old evolved stars (≳Gyr). The overlap with a young stellar population, containing stars of up to ≈20 M⊙, may implicate a neutron star/magnetar produced in the core collapse of a massive star as the source of FRB 20250316A.

Keywords: Stellar populations, Star forming regions, Compact objects, Infrared sources, Radio transient sources
Lonely Little Red Dots: Challenges to the Active Galactic Nucleus Nature of Little Red Dots through Their Clustering and Spectral Energy Distributions. Observations with the James Webb Space Telescope reveal a previously unseen population of compact red objects, known as "little red dots" (LRDs). We study a new photometrically selected sample of 124 LRDs in the redshift range z ∼ 3─10 selected from Near Infrared Camera coverage of the Cosmic Evolution Early Release Science Survey (CEERS), North Ecliptic Pole Time Domain Field (NEP-TDF), James Webb Space Telescope Advanced Deep Extragalactic Survey (JADES), and JEMS. For JADES, the NEP-TDF, and CEERS, we compare spectral energy distribution (SED) models with and without active galactic nucleus (AGN) components and analyze the impact of an AGN component on the goodness of fit using the Bayesian information criterion (BIC). We find that while the χ2 of the majority of models containing AGN components is improved compared to models without AGN components, we show that the BIC suggests that models without AGN are a more appropriate fit to LRD SEDs, especially when MIRI data are available. We also measure LRD clustering in the CEERS field, JADES field, and NEP-TDF, where we compare the spatial distribution of LRDs and galaxies with Kolmogorov─Smirnov tests of equality of distribution. We find that the neighbourhood of LRDs tends to be less dense compared to galaxies at all selections and masses and at similar redshifts. We further measure upper limit estimates for the halo masses of LRDs using abundance matching. While the population of LRDs could be a mixture of several different inherent populations, as a whole, it does appear that these systems are mostly hosting compact galaxies or star clusters in formation.

Keywords: AGN host galaxies, James Webb Space Telescope, Active galactic nuclei, High-redshift galaxies, Galaxies
The Discovery of 25 μm Interstellar Methanol. We present the first astrophysical detection of methanol (CH3OH) in the torsional band near 25 μm. Using high-resolution mid-infrared (MIR) spectroscopy, we identified over 70 gas-phase CH3OH absorption lines between 20 and 28 μm toward the massive protostar NGC 7538 IRS 1 with the Stratospheric Observatory for Infrared Astronomy/Echelon-Cross-Echelle Spectrograph. We derive a temperature of 180 K and a total column density of 2 × 1017 cm‑2, comparable to submillimeter measurements. Complementary analysis of acetylene (C2H2) absorption lines is also included. Both CH3OH and C2H2 reveal an unresolved second velocity component. These MIR absorption lines likely probe the molecular material in two edge-on disks, supporting the scenario that NGC 7538 IRS 1 consists of multiple protostars. We provide an updated line list for the torsional band of CH3OH, which was generated from lab work and model calculations. This discovery and the updated line list will enable the search for CH3OH in JWST/MIRI spectra.

Keywords: High resolution spectroscopy, Spectral line lists, Molecular spectroscopy, Astrochemistry, Young stellar objects, Star formation, Interstellar medium, Protostars