Sazuna/UAT_keywords huggingface dataset:
Geminga: A Window into the Role Played by the Local Halo in the Cosmic-Ray Propagation Process. A novel phenomenon among the recently observed Geminga pulsar halo is the presence of distinct radiation morphology at high energies, while no extended radiation is detected in the 10–500 GeV energy band within a 40° × 40° region. This phenomenon suggests that pulsar halos play a crucial role in the local propagation of cosmic rays, making it necessary to investigate the underlying mechanisms of this phenomenon. This work focuses on the 3D propagation study of cosmic rays, incorporating the Geminga pulsar into our propagation framework to investigate its contribution to different observational spectra. We consider Geminga a dominant local source of positrons, partially reproducing the observed positron spectrum and multiwavelength radiative spectra of the Geminga halo. Through calculations of signal and background at different angles, we find that: (1) the slow-diffusion properties near the Geminga pulsar and its proper motion may cause the radiation from electrons originating from Geminga to be distributed across a more extended region, and (2) the incomplete subtraction of radiation from the local halo may contribute, to some extent, to the diffuse gamma-ray fluctuations detected by LHAASO. We hope that LHAASO will detect more sources of cosmic-ray halo to further validate our model.

Keywords: Galactic cosmic rays, Diffuse radiation, Gamma-rays
AT2022sxl: A Candidate Repeating Tidal Disruption Event in Possible Association with Two High-energy Neutrino Events. We report a candidate repeating tidal disruption event (TDE), AT2022sxl, found from large-field optical survey data. Two flares with a separation time of ∼7.2 yr between the two optical peaks are observed. Related mid-infrared (MIR) flares, with delay times of ∼200 days are also seen. We analyze two optical spectra of the TDE source, one near the optical peak of the second flare from the Transient Name Server and one at the quiescent flux level after the second flare. The latter was taken by us with the 10.4 m Gran Telescopio Canarias. Comparing the features of the two spectra, we identify that the host is likely a composite galaxy at redshift 0.23, and the TDE event, probably an H+He type, mainly powered broad components in the emission lines of Hα, Hβ, and He I λ5876. More interestingly, we find that two Bronze-type neutrino events, detected by the IceCube neutrino observatory, match the TDE in position and the second flare, especially the delayed MIR flare, in time. We discuss the MIR luminosity properties of the currently reported (candidate) neutrino-emitting TDEs and suggest that luminous MIR emission is a prerequisite for neutrino production in TDEs.

Keywords: Neutrino astronomy, Tidal disruption
The Role of Rotation on the Yields of the Two γ-Ray Emitters <SUP>26</SUP>Al and <SUP>60</SUP>Fe Ejected by Massive Stars. We show that the observed 60Fe/26Al flux ratio provided by the SPectrometer on INTEGRAL satellite (0.24 ± 0.04) can be reproduced only if rotation is taken into account in the computation of the stellar models. Predictions from nonrotating stellar models yield a significantly lower ratio (0.062), which is incompatible with the observed value. The adopted models and the associated yields are based on a combination of models already published by M. Limongi &amp; A. Chieffi, complemented by additional ones fully consistent with the original grid, allowing a finer resolution in the initial rotational velocity distribution.

Keywords: Explosive nucleosynthesis, Nucleosynthesis, Massive stars, Nuclear astrophysics, Stellar nucleosynthesis, Stellar rotation, Gamma-ray astronomy, Stellar evolution
Radiation-hydrodynamics Effects in an Inhomogeneous Medium. Radiation flow through an inhomogeneous medium is critical in a wide range of physics and astronomy applications, from transport across cloud layers on the Earth to the propagation of supernova blast waves producing ultraviolet and X-ray emission. Radiation interacts with matter, driving hydrodynamic feedback that further alters the radiation characteristics (energy and angular distribution). This paper reviews the current state of the art in the modeling of inhomogeneous radiation transport, subgrid models developed to capture this often-unresolved physics, and the experiments designed to improve our understanding of these models. This paper focuses on simulations based on upcoming experiments designed to test this physics. We present a series of detailed simulations (both single-clump and multi-clump conditions) probing the dependence on the physical properties of the radiation front (e.g., radiation energy) and material characteristics (specific heat, opacity, clump densities). We find that, unless the radiation pressure is high, the clumps will heat and then expand, effectively cutting off the radiation flow. The expanding winds can also produce shocks that generates high-energy emission. We compare our detailed simulations with some of the current subgrid prescriptions, identifying some of the limitations of these current models.

Keywords: Radiative transfer simulations, Supernovae, Radiative transfer
Full-sky Models of Galactic Microwave Emission and Polarization at Subarcminute Scales for the Python Sky Model. Polarized foreground emission from the Galaxy is one of the biggest challenges facing current and upcoming cosmic microwave background (CMB) polarization experiments. We develop new models of polarized Galactic dust and synchrotron emission at CMB frequencies that draw on the latest observational constraints; that employ the "polarization fraction tensor" framework to couple intensity and polarization in a physically motivated way; and that allow for stochastic realizations of small-scale structure at subarcminute angular scales currently unconstrained by full-sky data. We implement these models into the publicly available Python Sky Model (PySM) software and additionally provide PySM interfaces to select models of dust and CO emission from the literature. We characterize the behavior of each model by quantitatively comparing it to observational constraints in both maps and power spectra, demonstrating an overall improvement over previous PySM models. Finally, we synthesize models of the various Galactic foreground components into a coherent suite of three plausible microwave skies that span a range of astrophysical complexity allowed by current data. Author contributions to this paper can be found at the end of this work.

Keywords: Interstellar dust, Interstellar thermal emission, Cosmic microwave background radiation, Interstellar synchrotron emission, Diffuse molecular clouds, Diffuse interstellar clouds
Discovery of SiC and Iron Dust around AGB Stars in the Very Metal-poor Sextans a Dwarf Galaxy with JWST: Implications for Dust Production at High Redshift. Low-resolution infrared spectroscopy from JWST confirms the presence of SiC and likely metallic iron dust around asymptotic giant branch (AGB) stars in the Sextans A dwarf galaxy, which has a metallicity ∼1%─7% Z⊙. While metal-poor carbon-rich AGB stars are known to produce copious amounts of amorphous carbon dust owing to the dredge up of newly synthesized carbon, this is the first time that Si- and Fe-bearing dust has been detected at this extreme metallicity. Of the six AGB stars observed, one is an intermediate-mass (∼1.2─4 M⊙) carbon star showing SiC dust, and another is an oxygen-rich M-type star with mass ∼4─5 M⊙ that is likely undergoing hot bottom burning. The infrared excess of the M-type star is strong, but featureless. We tested multiple dust species, and found that it is best fit with metallic iron dust. Assuming its dust-production rate stays constant over the final 2─3 × 104 yr of its evolution, this star will produce ∼0.9─3.7 times the iron dust mass predicted by models, with the range depending on the adopted stellar mass. The implications for dust production in high-redshift galaxies are potentially significant, especially regarding the assumed dust species used in dust evolution models and the timescale of AGB dust formation. Stars on the upper end of the AGB mass range can begin producing dust as early as 30─50 Myr after they form, and they may therefore rival dust production by supernovae at high redshift.

Keywords: Carbon stars, Dwarf galaxies, James Webb Space Telescope, Asymptotic giant branch stars, Circumstellar dust
Serendipitous Discovery of a Young Cluster of Galaxies at z ∼ 0.5 Projected Next to the Nearby Tadpole Galaxy KUG 1138 + 327. Using a 90 ks Chandra ACIS-S observation in the 0.3–7 keV band, along with complementary Low-Frequency Array and Karl G. Jansky Very Large Array data in the 120–168 MHz and 1–2 GHz ranges, we study the diffuse emission around the nearby dwarf galaxy KUG 1138+327. Our analysis reveals a diffuse X-ray feature on the southern side, disconnected from the galactic disk. This feature exhibits a hard X-ray spectrum, which is highly unusual for an outflow from a dwarf galaxy. We interpret the irregularly shaped feature as hot plasma in a young galaxy cluster at redshift 0.5, supported by X-ray spectral fitting and consistent with the optical redshift of the central elliptical galaxy of a known cluster identified by a red sequence. Additionally, we detect a radio lobe east of the X-ray feature, likely produced by an active galactic nucleus (AGN) offset from the cluster center and confined primarily by ram pressure from the ambient medium. The lobe shows a steep nonthermal radio spectrum, suggesting a cosmic-ray age of ≳5 × 107 yr. Assuming energy equipartition between cosmic rays and magnetic fields, we estimate the lobe's total energy to be ∼9 × 1056 erg, comparable to the thermal energy in the same volume. This study thus identifies a background young cluster projected next to KUG 1138+327 and highlights the potentially significant role of off-center AGN feedback in shaping the intracluster medium.

Keywords: Galaxy clusters
Parallel Collisionless Shocks in Strongly Magnetized Electron─Ion Plasma. I. Temperature Anisotropies. Collisionless electron─ion shocks are fundamental to astrophysical plasmas, yet their behavior in strong magnetic fields remains poorly understood. Using particle-in-cell simulations with the SHARP-1D3V code, we investigate the role of the ion magnetization parameter σi in parallel shock transitions. Strongly magnetized converging flows (σi &gt; 1) exhibit lower-density compression ratios (R ∼ 2), smaller entropy jumps, and suppressed particle acceleration while maintaining pressure anisotropy stability due to conserved perpendicular temperatures across the transition region, alongside increased parallel temperatures. In contrast, weakly magnetized shocks drive downstream mirror and firehose instabilities due to ion temperature anisotropy, which are suppressed in strongly magnetized cases. Additionally, weakly magnetized shocks exhibit the onset of a suprathermal population induced by shock-drift acceleration, with most of the upstream kinetic energy thermalized for both electrons and ions in the downstream region. Our results demonstrate that perpendicular temperatures for both species are conserved in weakly and strongly magnetized cases and highlight deviations from standard ideal magnetohydrodynamic behavior in strongly magnetized cases. These findings provide critical insights into the role of magnetic fields in parallel collisionless astrophysical shocks.

Keywords: Shocks, Plasma astrophysics, Space plasmas
The X-Ray Variability and Luminosity Function of High-mass X-Ray Binaries in the Dwarf Starburst Galaxy IC 10. We present an analysis of ∼235 ks of Chandra observations obtained over ∼19 yr of the nearby dwarf starburst galaxy IC 10 in order to study the X-ray variability and X-ray luminosity function (XLF) of its X-ray binary (XRB) population. We identify 23 likely XRBs within the Two Micron All Sky Survey KS isophotal radius and find the distributions of their dynamic ranges and duty cycles are consistent with a young, high-mass XRB (HMXB) population dominated by supergiant-fed systems, consistent with previous work. In general, we find that brighter HMXBs (those with LX ≳ several ×1036 erg s−1) have higher duty cycles (i.e., are more persistent X-ray sources) than fainter objects, and the dynamic ranges of the sgHMXBs in the lower-metallicity environment of IC 10 are higher than what is observed for comparable systems in the Milky Way. After filtering out foreground stars on the basis of Gaia parallaxes, we construct, for the first time, the XLF of IC 10. We then use the XLF to model the star formation history of the galaxy, finding that a very recent (3─8 Myr) burst of star formation with a rate of ∼0.5 M⊙ yr−1 is needed to adequately explain the observed bright end (LX ∼ 1037 erg s−1) of the HMXB XLF.

Keywords: Starburst galaxies, X-ray transient sources, Dwarf galaxies, High mass x-ray binary stars
Multiwavelength Study of HESS J0632+057: New Insights into Pulsar–Disk Interaction. We present an analysis of new multiwavelength observations of the TeV gamma-ray binary HESS J0632+057, conducted using SALT, Swift, NuSTAR, and VERITAS in 2023–2024. By combining these new data with archival observations, we confirm previous suggestions of orbital variability in the source's X-ray spectrum, including increased X-ray absorption at the orbital phase interval of ϕ ≈ 0.3–0.4. The source's X-ray flux within this phase interval seems to have exhibited a significant change on an orbital timescale. Additionally, occasional short-term variations in the X-ray band on a timescale of less than 3 days have been observed. The measured duration of the increased absorbing column density and the flux variability timescales can provide clues about the interaction between the putative pulsar and the Be companion's disk if, as previously suggested, the pulsar crosses the disk at this phase interval. Moreover, the new contemporaneous X-ray and TeV observations around the pulsar-crossing phases revealed independent variability in the X-ray and TeV fluxes, contrary to a previous observation of concurrent flux increases. While these observations alone cannot provide definitive conclusions, we discuss our results in the context of pulsar–disk interaction and intrabinary shock emission scenarios.

Keywords: X-ray astronomy, Optical observation, X-ray binary stars, High energy astrophysics, Gamma-ray sources, X-ray sources, Circumstellar disks, Gamma-ray astronomy
Numerical Approach to Compressible Shallow-water Dynamics of Neutron-star Spreading Layers. A weakly magnetized neutron star (NS) undergoing disk accretion should release about half of its power in a compact region known as the accretion boundary layer. Latitudinal spread of the accreted matter and efficient radiative cooling justify the approach to this flow as a two-dimensional spreading layer (SL) on the surface of the star. Numerical simulations of SLs are challenging because of the curved geometry and supersonic nature of the problem. We develop and test a new two-dimensional hydrodynamics code, SPLASH, which uses the multislope second-order Monotonic Upstream-centered Scheme for Conservation Law scheme in combination with an HLLC+ Riemann solver on an arbitrary irregular mesh on a spherical surface. The code is suitable and accurate for Mach numbers up to 5–10. Adding sinks and sources to the conserved variables, we simulate early stages of constant-rate accretion onto a spherical NS. During these stages of accretion, heating in the equatorial region triggers convective instability that causes rapid mixing in the latitudinal direction. One of the outcomes of the instability is the development of a "tennis ball" pattern rotating at a frequency considerably different from the rotation frequency of the matter. In the simulated variability curves, there are signatures of both the pattern rotation and the rotation of the SL, as well as their harmonics. The pattern and cyclonal vortices associated with it are probably a manifestation of an inertial oscillation mode excited within the layer (https://github.com/TURBOLOSE/SPLASH).

Keywords: Neutron stars, Computational astronomy, Hydrodynamics, Stellar accretion, Low-mass x-ray binary stars, Astrophysical fluid dynamics
Tracing Red Giant Members of the Globular Cluster Palomar 5 with APOGEE and Gaia. The globular cluster Palomar 5 (Pal 5) is in the process of being tidally shredded as it orbits the Milky Way. Its core is currently at a heliocentric distance of ∼21 kpc, near apogalacticon (∼18 kpc), and it reaches ∼5─7 kpc at perigalacticon. Pal 5's leading and trailing arms stretch over 20° on the sky, making them sensitive probes of the Milky Way's mass distribution. In this work, we search for red giant members of Pal 5 using spectroscopic data from APOGEE DR17 and photometric and astrometric data from Gaia data release 3. Based on position and proper motion, we identify eight members of Pal 5: six in the core and two in the stream. The clustering algorithm HDBSCAN finds these same eight. We then use chemical tagging with APOGEE abundances to search for additional members across five APOGEE fields overlapping Pal 5. While several dozen candidates are identified, most deviate (some significantly) from known kinematic and color─magnitude trends, suggesting that they are less likely to be true members. We estimate the expected number of giants in the APOGEE pointings based on the area and stellar mass of the streams. Given APOGEE's limiting magnitude, we find that few, if any, new giants are expected, especially if the stream is more diffuse at these locations. Our results support the presence of density variations in Pal 5's tidal streams, consistent with earlier studies attributing such features to baryonic perturbers in the Milky Way, dark matter subhalos, or interactions with passing globular clusters.

Keywords: Globular star clusters, Milky Way stellar halo, Milky Way dynamics, Chemical abundances
Kinematical Modeling of the Resolved Stellar Outskirts of M32: Constraints on Tidal Stripping Scenarios. As the only compact elliptical close enough to resolve into individual stars, the satellite dwarf galaxy M32 provides a unique opportunity for exploring the origins of such rare galaxies. In this work, we combined archival and novel Keck/DEIMOS spectroscopy from a southern extension of the Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo (SPLASH) survey with optical HST imaging from the Panchromatic Hubble Andromeda Southern Treasury (PHAST) survey. The resulting sample of 2505 giant stars is unprecedented both in size and spatial coverage (0 .' 9─15 .' 5, or out to ∼23reff and ∼30reff along M32's major and minor axes) for probing the resolved stellar outskirts of M32. Given the structurally complex region near M32 on the sky, we modeled M32's line-of-sight kinematics simultaneously alongside M31's rotating stellar disk and potential outliers corresponding to M31's kinematically hot stellar halo and/or tidal substructure. Inside the radius corresponding to the observed twisting of isophotal contours in M32's surface brightness profile (Riso ∼ 5reff ∼ 150" or 0.56 kpc), M32 exhibits a line-of-sight velocity distribution characteristic of ordered rotation, transitioning to a distribution with heavier outliers beyond this radius. Within Riso, the rotational direction is aligned with M32's major-axis rotation, but shifts to become roughly aligned with M32's minor axis beyond Riso. We interpret these kinematical signatures in the stellar outskirts of M32 as evidence of tidal distortion from interactions with M31 and discuss their implications for M32 formation pathways.

Keywords: Galaxy formation, Stellar kinematics, Dwarf elliptical galaxies, Compact dwarf galaxies, Andromeda Galaxy
Unveiling the Cosmic Gems Arc at z ∼ 10 with JWST NIRCam. We present recent JWST NIRCam imaging observations of SPT0615-JD (also known as the Cosmic Gems Arc), lensed by the galaxy cluster SPT-CL J0615−5746. The 5″ long arc is the most highly magnified z &gt; 10 galaxy known. It straddles the lensing critical curve and reveals five star clusters with radii of ∼1 pc or less. We measure the full arc to have F200W 24.5 AB mag, consisting of two mirror images, each 25.3 AB mag with a median magnification of  μ∼60−8+17  (delensed 29.7 AB mag, MUV = −17.8). The galaxy has an extremely strong Lyman break F115W−F200W &gt;3.2 mag (2σ lower limit), is undetected in all bluer filters (&lt;2σ), and has a very blue continuum slope redward of the break (β = −2.7 ± 0.1). This results in a photometric redshift zphot = 10.2 ± 0.2 (95% confidence) with no significant likelihood below z &lt; 9.8. Based on spectral energy distribution fitting to the total photometry, we estimate an intrinsic stellar mass of M* ∼ 2.4─5.6 × 107 M⊙, young mass-weighted age of ∼21─79 Myr, low dust content (AV &lt; 0.15), and a low metallicity of ≲1% Z⊙. We identify a fainter third counterimage candidate within 2 .″ 2 of the predicted position, lensed to AB mag 28.4 and magnified by μ ∼ 2, suggesting the fold arc may only show ∼60% of the galaxy. SPT0615-JD is a unique laboratory to study star clusters observed within a galaxy just 460 Myr after the Big Bang.

Keywords: Galaxy clusters, Early universe, Galaxy formation, Strong gravitational lensing, Galaxy evolution, High-redshift galaxies
Extreme Jet Beaming Observed in Neutrino-associated Blazars. Bright blazars were found to be prominent neutrino sources, and a number of IceCube events were associated with them over recent years. A particularly strong observational connection is present between neutrinos and blazars with bright, Doppler-boosted, parsec-scale radio emission. In this work, we further explore the nature of this connection by examining the jet geometry and kinematics of neutrino-associated blazars. We find that these blazars demonstrate remarkably strong jet beaming, even compared to other radio-bright sources. Their Doppler and Lorentz factors are larger, and viewing angles are smaller than for other blazars in the complete uniformly selected MOJAVE sample. Observationally, this serves as yet another piece of evidence for blazars forming a major population of neutrino sources. The strong neutrino─beaming correlation indicates that high-energy neutrino velocity is predominantly oriented along the jet, and the original PeV-scale protons exhibit a relativistic bulk motion along the jet. It suggests that neutrino production happens not too close to the black hole, but rather at subparsec distances, where the jet is already accelerated.

Keywords: Radio jets, Blazars, Neutrino astronomy, Very long baseline interferometry, Relativistic jets, Astrostatistics, Active galactic nuclei