Sazuna/UAT_keywords huggingface dataset:
Signatures of Magnetic Flux Expulsion from Neutron Star Cores. Shortly after a neutron star is born, the protons in its core begin to form a superconductor. In terrestrial materials, the hallmark of superconductivity is an associated expulsion of magnetic flux, but whether this expulsion process can be effective in neutron stars remains an open question—one with major implications for the phenomenology of pulsars and magnetars. Earlier theoretical arguments suggested flux must be trapped within the core, yet models of magnetars rely on it being expelled from the core and confined to the crust, where it can evolve on kiloyear timescales. We show that if expulsion is not complete, a qualitatively new evolutionary branch for neutron stars arises, which can account for the properties of newly discovered long-period radio transients and fast radio bursts in older environments. One recently proposed model that could create such field topologies has additional implications for gravitational-wave emission and predicts a characteristic energy release that, if observed, will corroborate the role of reconnection at the onset of superconductivity and can constrain the superconducting proton gap.

Keywords: Neutron star cores, Stellar magnetic fields, Radio transient sources
Overestimated Pressure Broadening Misleads Model Spectra in Cool M Dwarf Stars. Available one-dimensional stellar models fail to reproduce the observed spectrum of the ultracool M dwarf TRAPPIST-1. In particular, current models predict strong iron hydride (FeH) absorption due to the Wing─Ford bands at 0.99 μm, yet this spectral feature is only weakly present in TRAPPIST-1 and other mid-to-late M dwarf stars. Additionally, the shape of the continuum between the water bands in the near-infrared does not match between models and observations. Here, we show that assumptions about pressure broadening, specifically van der Waals broadening, have a dramatic effect on modeled broadband spectral features. We use Merged Parallelized Simplified-ATLAS to generate synthetic spectra over a range of van der Waals broadening strengths, adopting 1D PHOENIX temperature─pressure structures. We find that minimal broadening best matches the observed FeH profile at 0.99 μm and in the pseudocontinuum between the large water bands. These results suggest that broadening prescriptions derived for Sun-like stars are not valid for lower-mass stars and that pressure broadening for molecular lines in cool stellar atmospheres must be reevaluated. Refining pressure broadening treatments will improve the accuracy of M dwarf spectral models, enabling more reliable determinations of stellar properties and atmospheric compositions of planets orbiting M dwarfs.

Keywords: M dwarf stars
First Associated Neutrino Search for a Failed Supernova Candidate with Super-Kamiokande. In 2024, a failed supernova (SN) candidate, M31-2014-DS1, was reported in the Andromeda galaxy (M31), located at a distance of approximately 770 kpc. In this Letter, we search for neutrinos from this failed SN using data from Super-Kamiokande (SK). Based on the estimated time of black hole formation inferred from optical and infrared observations, we define a search window for neutrino events in the SK data. Using this window, we develop a dedicated analysis method for failed SNe and apply it to M31-2014-DS1, by conducting a cluster search using the timing and energy information of candidate events. No significant neutrino excess is observed within the search region. Consequently, we place an upper limit on the time-integrated electron antineutrino luminosity from M31-2014-DS1 and discuss its implications for various failed SN models and their neutrino emission characteristics. Despite the 18 MeV threshold adopted to suppress backgrounds, the search remains sufficiently sensitive to constrain the Shen-TM1 equation of state, in a more optimistic emission scenario with progenitor stars of 40 M⊙ and relatively high mean electron-antineutrino energies of about 23.2 MeV, yielding a 90% confidence level upper limit of 1.76 × 1053 erg on the time-integrated electron antineutrino luminosity, moderately above the expected value of 1.35 × 1053 erg.

Keywords: Neutrino astronomy, Andromeda Galaxy, Gravitational collapse, Core-collapse supernovae
The Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the Ultraviolet to the Near-infrared. We present an extensive photometric and spectroscopic ultraviolet─optical─infrared campaign on the luminous fast blue optical transient (LFBOT) AT 2024wpp over the first ∼100 days. AT 2024wpp is the most luminous LFBOT discovered to date, with Lpk ≍ (2─4) × 1045 erg s−1 (5─10 times that of the prototypical AT 2018cow). This extreme luminosity enabled the acquisition of the most detailed LFBOT UV light curve thus far. In the first ∼45 days, AT 2024wpp radiated &gt;1051 erg, surpassing AT 2018cow by an order of magnitude and requiring a power source beyond the radioactive 56Ni decay of traditional supernovae. Like AT 2018cow, the UV─optical spectrum of AT 2024wpp is dominated by a persistently blue thermal continuum throughout our monitoring, with blackbody parameters at a peak of T &gt; 30,000 K and RBB/t ≍ 0.2c─0.3c. We find evidence for cooling until ∼10 days; thereafter, T ≳ 20,000 K is maintained. We interpret the featureless spectra as a consequence of continuous energy injection from a central source of high-energy emission that maintains high ejecta ionization. After 35 days, faint (equivalent width (EW) ≲ 10 Å) H and He spectral features with kinematically separate velocity components centered at 0 and −6400 km s−1 emerge, implying spherical symmetry deviations. A near-infrared excess of emission above the optical blackbody emerges between 20 and 30 days, with a power-law spectrum Fν,NIR ∝ ν−0.3 at 30 days. We interpret this distinct emission component as either reprocessing of early UV emission in a dust echo or free─free emission in an extended medium above the optical photosphere. LFBOT asphericity and multiple outflow components (including mildly relativistic ejecta), together with the large radiated energy, are naturally realized by super-Eddington accretion disks around neutron stars or black holes and their outflows.

Keywords: Transient sources, High energy astrophysics
Kelvin─Helmholtz Instability and Energetic Neutral Atoms in the Heliosphere. The Interstellar Mapping and Acceleration Probe (IMAP) mission launched from Earth on 2025 September 24, beginning its commissioning phase as the spacecraft makes its way to Lagrange Point 1. IMAP-Hi, one of three energetic neutral atom (ENA) imagers, has improved capabilities compared to its predecessor, the Interstellar Boundary Explorer-Hi instrument, such as a wider energy coverage (∼0.4─15.6 keV compared to ∼0.5─6 keV). In this study, we aim to simulate ENA emissions from the heliosphere, at IMAP-Hi energies, with the goal of showing what ENA maps may look like when their source is affected by the presence of the Kelvin─Helmholtz instability (KHI). The KHI arises when the fast and slow solar wind meet in the heliosheath near the heliopause and create a shear flow, usually strongest at high latitudes. According to our simulation, if the KHIs are present in the heliosphere, then IMAP-Hi should be able to observe their effects on ENA emissions via long bands of enhanced ENA fluxes at high northern and southern latitudes, reaching all the way back to the tail. These bands are separated on the order of ∼15° in latitude, depending on the direction in the sky. The ENA bands are most visible at ∼2─6 keV. The presence or absence of ENA bands in IMAP-Hi observations and their orientation may not only provide important information about the structure of the heliosphere, but also guide improvements to our models, since these features differ or are not present among various simulations.

Keywords: Heliopause, Slow solar wind, Solar cycle, Heliosphere, Fast solar wind, Solar wind, Pickup ions, Heliosheath
The First X-Ray Polarimetry of GRS 1739─278 Reveals Its Rapidly Spinning Black Hole. We present a joint spectropolarimetric analysis of the black hole X-ray binary GRS 1739─278 during its 2025 mini-outburst, using simultaneous observations from IXPE and NuSTAR. The IXPE data show a polarization degree (PD) of PD = (2.3% ± 0.4%) and polarization angle (PA) of PA = 62° ± 5° in the 2−8 keV range. The model-independent analysis reveals that PD increases from ∼2% at 2 keV to ∼10% in the 6─8 keV band, while PA remains stable across the IXPE band within statistical uncertainties. Broadband spectral modeling of the combined IXPE and NuSTAR datasets shows that hard Comptonization contributes negligibly in this soft-state observation, while a substantial reflected component is required in addition to the thermal disk emission. We then model the IXPE Stokes spectra using the kynbbrr model. The best fits indicate that high-spin configurations enhance the contribution of the reflected returning radiation, which dominates the observed polarization properties. From the kynbbrr modeling, we infer an extreme black hole spin of  a=0.994−0.003+0.004  and a system inclination of  i=54°−4°+8° . Owing to the large contribution from the returning radiation, the observed polarization direction is nearly parallel to the projected system axis, the position angle of which is predicted at 58° ± 4°. Our results demonstrate that X-ray polarimetry, combined with broadband spectroscopy, directly probes the geometry and relativistic effects in accretion disks around stellar-mass black holes.

Keywords: Accretion, Polarimetry, X-ray astronomy, Stellar mass black holes
Strong Evidence for Cosmic-Ray-supported ∼L* Galaxy Halos via X-Ray and tSZ Constraints. Many state-of-the-art galaxy simulations featuring traditional feedback modes have significant challenges producing enough extended soft X-ray (∼0.5−2 keV) emission at R ∼ 0.5Rvir−1Rvir observed around galaxies with stellar masses M* ≲ 1011 M⊙, without violating galaxy mass function constraints. Moreover, thermal Sunyaev─Zel'dovich (tSZ) measurements probing the thermal pressure of similar galaxies indicate that it is orders of magnitude lower than predictions from simple halo hydrodynamics and many hydrodynamical simulations. We demonstrate that these constraints can be met congruously with a large nonthermal pressure contribution in the form of cosmic rays (CRs) from supernovae and/or active galactic nuclei (AGN), which lowers the tSZ signal, while CR leptons produce plentiful soft X-rays via inverse Compton scattering of the cosmic microwave background. The combination of these two observations is far more constraining on the pressure budget of galactic halos than either alone—if these novel tSZ and X-ray observations are borne out by future studies, then taken together they reveal the strongest evidence for CR support in halos to date. Conversely, it is very difficult to produce the extended X-rays via traditional thermal emission without increasing the overall thermal pressure and thus tSZ signal in tandem, making these tensions even worse. Finally, tSZ and X-rays together unlock a novel observational method to constrain halo CR pressure relative to thermal pressure, with implications for CR transport parameters and AGN feedback energetics across various galaxy mass scales. Taking the currently observed constraints at Mhalo ∼ 1012 M⊙ imply that the halo CR pressure must at least be equal to the gas thermal pressure.

Keywords: High energy astrophysics, Galaxy evolution, Circumgalactic medium, Galaxies, Cosmic rays
Proton-rich Production of Lanthanides: The vi Process. The astrophysical origin of the lanthanides is an open question in nuclear astrophysics. Besides the widely studied s, i, and r processes in moderately to strongly neutron-rich environments, an intriguing alternative site for lanthanide production could in fact be robustly proton-rich matter outflows from core-collapse supernovae under specific conditions—in particular, high-entropy winds with enhanced neutrino luminosity and fast dynamical timescales. In this environment, excess protons present after charged-particle reactions have ceased can continue to be converted to neutrons by (anti)neutrino interactions, producing a neutron-capture reaction flow up to A ∼ 200. This scenario, christened the νi process in a recent paper, has previously been discussed as a possibility. Here, we examine the prospects for the νi process through the lenses of stellar abundance patterns, bolometric light curves, and galactic chemical evolution models, with a particular focus on hypernovae as candidate sites. We identify specific lanthanide signatures for which the νi process can provide a credible supplement to the r/i processes.

Keywords: Supernova neutrinos, Hypernovae, Nucleosynthesis, Neutrino oscillations, Core-collapse supernovae, R-process, Light curves, Galaxy chemical evolution, Stellar abundances, P-process, CEMP stars
New Evidence for Extragalactic Einstein Probe Transients Associated with Long Gamma-Ray Bursts. The origin of extragalactic fast X-ray transients (EFXTs) remains a fundamental open question in high-energy astrophysics. The Einstein Probe (EP) mission provides a transformative opportunity to investigate their nature. While mounting observations of EP-discovered EFXTs (EP-EFXTs) suggest a possible connection to long gamma-ray bursts (lGRBs), an in-depth comparative analysis between them remains lacking. Here, we present a comparative analysis of their cosmic formation histories, revealing that EP-EFXTs and lGRBs share a similar evolutionary trend—showing a marked decline at z &lt; 1.0 and a plateau beyond 1.0 &lt; z &lt; 5—that clearly distinguishes them from short GRBs. This result is derived from a rigorously selected sample of EP-EFXTs, using Lynden-Bell's c− method to reconstruct, for the first time, the luminosity function and formation rate of EP-EFXTs without any assumptions. Our findings provide independent evidence that EP-EFXTs and lGRBs may originate from a common progenitor channel.

Keywords: X-ray astronomy, X-ray transient sources, Gamma-ray bursts, Star formation
Compact Ca II K Brightenings Precede Solar Flares: A Dunn Solar Telescope Pilot Study. We present a uniform analysis of compact Ca II K (3934 Å) brightenings that occur near flare kernels and assess their value as short-lead indicators of solar flare onset. Using high-cadence imaging from the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope, we examine eight flare sequences (seven C-class and one B-class) obtained between 2021 and 2025. Fixed, detector-coordinate regions of interest are used to generate mean-intensity light curves, which are detrended and smoothed to isolate impulsive brightenings. In every event, a compact Ca II K brightening is detected within or adjacent to the flaring region that peaks 10─45 minutes before the primary kernel and the corresponding rise in GOES 1─8 Å flux. The measured temporal offsets scale with the deprojected separation between the brightening and flare kernels, implying an apparent propagation speed of ∼30─35 km s−1 that is consistent with chromospheric reconnection. Complementary Spectropolarimeter for Infrared and Optical Regions spectropolarimetry for one event shows topological reconfiguration from closed to open or extended connectivity, supporting a reconnection-driven origin. These results demonstrate that compact Ca II K brightenings are reproducible, physically meaningful precursors to flare onset. Their simplicity and cadence make them attractive chromospheric indicators, and future work will evaluate their predictive skill alongside established UV/EUV and magnetic diagnostics.

Keywords: Solar flares, Space weather, Solar spectral irradiance, Solar physics, Solar chromosphere
Spectral Shapes of Pair Annihilation Line Emission in Magnetar Giant Flares. We investigate the gamma-ray spectrum in the MeV range arising from electron─positron pair annihilation in fireballs associated with magnetar giant flares (MGFs), motivated by the recent observation of a MeV gamma-ray line feature in a bright gamma-ray burst, GRB 221009A. We develop an analytic model of line emission, demonstrating that relativistic beaming results in a broadened power-law spectral feature with a photon index of −1. We then perform Monte Carlo radiative transfer simulations incorporating electron─positron pair production, annihilation, and Compton scattering. The dependence of the emergent spectrum on the baryon loading is also examined, showing that a baryon-poor fireball is more favorable for the detection of MeV gamma rays. We further assess the detectability of the line component. The simulation results indicate that a power-law MeV component from the initial spike of a Galactic MGF could be observed with current instruments, such as Fermi/GBM, and will be well within the reach of upcoming MeV gamma-ray satellites, which are expected to detect  O(100)  photons from such events.

Keywords: Neutron stars, Magnetars, Gamma-ray transient sources, High energy astrophysics
First Cosmological Constraints from the Joint Analysis of Galaxy Clustering and the Kinetic Sunyaev─Zel'dovich Effect. We perform the first joint analysis of galaxy clustering (GC) and the kinetic Sunyaev─Zel'dovich (kSZ) effect to simultaneously constrain cosmological and astrophysical parameters in this work, utilizing a combination of an Atacama Cosmology Telescope Data Release 6 map and the Constant Stellar Mass (CMASS) galaxy sample. As a complementary probe to the galaxy density power spectrum, we incorporate the pairwise kSZ power spectrum detected with a high signal-to-noise ratio (S/N ∼ 7) to derive constraints on cosmological parameters ( H0=70.82−5.01+4.94 ,  Ωm=0.290−0.068+0.092 ,  w0=−1.038−0.437+0.245 ) and the average optical depth of the galaxy sample ( lgτ̄=−4.24±0.10 ). Compared to the GC-only analysis, the joint analysis yields tighter constraints on these cosmological parameters: the Figures of Merit improve by 20.5%, 19.7%, and 10.0% for the H0─Ωm, H0─w0, and Ωm─w0 contours, respectively. For the first time, we demonstrate the complementary applicability of the kSZ effect in constraining cosmological parameters from real observational data.

Keywords: Sunyaev-Zeldovich effect, Cosmological parameters from large-scale structure
Isotopic Ratios in the Disk of HD 163296. Isotopic abundance ratios in protoplanetary disks are critical for understanding volatile inheritance and chemical evolution in planet-forming environments. We present Atacama Large Millimeter/submillimeter Array observations of the rare isotopologue 13C18O(2─1) at ∼0 .″ 3 resolution from the disk around the Herbig Ae star HD 163296, combined with archival observations of C17O(2─1), C18O(1─0), and C17O(1─0), to empirically constrain carbon and oxygen isotopic ratios without detailed disk modeling. Both the C17O/13C18O(2─1) and C18O/C17O(1─0) flux ratios rise sharply across the CO snowline and flatten beyond 1 .″ 5 (r ≳ 150 au), where the emission becomes optically thin. This transition, reflecting a steep drop in CO column density set by the disk's thermal structure, makes HD 163296 an optimal case for isotopic analysis. Using beam-averaged intensities of the four transitions measured in this optically thin region, we derive isotopic ratios of 12C/13C =  75.3−11.4+14.7  and 18O/17O =  3.28−0.26+0.31 , both consistent with local interstellar medium values. The 16O/18O ratio remains weakly constrained due to moderate optical depth in the C18O(1─0) line and degeneracy with CO column density. These results demonstrate that rare CO isotopologues can provide robust, empirical constraints on isotopic ratios in disks when sharp structural transitions allow for the identification of optically thin regions, and establish HD 163296 as a benchmark for extending such studies to other systems with resolved snowline structures.

Keywords: Isotopic abundances, Protoplanetary disks, Astrochemistry
Resolving the Fe Kα Doublet of the Galactic Center Molecular Cloud G0.11-0.11 with XRISM. Fe Kα line emission from Galactic center molecular clouds can be produced either via fluorescence after illumination by an X-ray source or by cosmic-ray ionization. Unparalleled high-resolution X-ray spectroscopy obtained by XRISM/Resolve for the Galactic center molecular cloud G0.11-0.11 resolves its Fe Kα line complex for the first time, and points to a new method for discrimination between the X-ray reflection and cosmic-ray ionization models. The Fe Kα line complex is resolved into Fe Kα1 at E1 = 6.4040 keV and Fe Kα2 at E2 = 6.3910 keV. Both lines have noninstrumental FWHM of ≍3 eV, close to the predicted quantum mechanical width of the lines, suggesting scant other sources of line broadening other than instrumental and quantum effects. We measure a radial velocity of vLSR = 50 ± 12fit ± 14scale km s−1 for G0.11-0.11, achieving the same precision reached by radio observations of such clouds. The high-resolution spectrum tests for the presence of secondary Fe Kα lines, expected as a signature of cosmic-ray proton/ion ionization. The absence of the secondary lines argues against the cosmic-ray ionization model for G0.11-0.11. In the preferred X-ray reflection model, if the illuminating source is Sgr A⋆, the required luminosity for an X-ray outburst about 200 yr ago is L8 ≍ 1038 erg s−1 in an 8 keV wide band at 8 keV.

Keywords: High resolution spectroscopy, X-ray astronomy, Galactic center, Molecular clouds
A Millimeter Methanol Maser Ring Tracing the Deceleration of the Heat Wave Powered by the Massive Protostellar Accretion Outburst in G358.93─0.03 MM1. We present multiepoch, multiband Atacama Large Millimeter/submillimeter Array imaging of the new Class II millimeter methanol masers excited during the accretion outburst of the massive protostar G358.93−0.03 MM1. The highest angular resolution image (24 mas ≍160 au) reveals a nearly complete, circular ring of strong maser spots in the 217.2992 GHz (vt = 1) maser line that closely circumscribes the dust continuum emission from MM1. Weaker maser emission lies inside the eastern and southern halves of the maser ring, generally coincident with the centimeter masers excited during the outburst but avoiding the densest parts of the hot core gas traced by high excitation lines of CH3CN. Using a variety of fitting techniques on the image cubes of the two strongest maser lines, each observed over three to four epochs, we find the diameter of the ring increased by ≳60% (from ≍1100 to ≍1800 au in the 217 GHz line) over 200 days, consistent with an average radial propagation rate of ≍0.01c, while the maser intensity declined exponentially. Fitting the angular extent of the millimeter masers versus time yields a power law of index 0.39 ± 0.06, which also reproduces the observed extent of the 6.7 GHz masers in the first very long baseline interferometry epoch of R. A. Burns et al. 2020 This exponent is consistent with the prediction of radius versus time in the Taylor─von Neumann─Sedov self-similar solution for an intense spherical explosion from a point source (R ∝ t2/5). These results demonstrate the explosive nature of accretion outbursts in massive protostars and their ability to generate subluminal heat waves traceable by centimeter and millimeter masers for several months as the energy traverses the surrounding molecular material.

Keywords: Millimeter astronomy, Star formation, Astrophysical masers, Stellar accretion, Protostars, Radio interferometry, Complex organic molecules