Sazuna/UAT_keywords huggingface dataset:
Pair Cascades in Magnetar Magnetospheres. Resonant inverse Compton scattering (RICS) of soft thermal photons by relativistic particles on closed magnetic field loops has been proposed to explain the hard emission observed up to and beyond 200 keV from magnetars. If particles injected at the base of the loops have Lorentz factors ≳102, the RICS spectra will be attenuated by both one-photon pair production and photon splitting in the ultrastrong magnetar fields, producing additional spectral components from pair synchrotron radiation and split photons that produce further generations of pairs and split photons. We investigate such cascades initiated by the primary injected electrons through a Monte Carlo simulation, and study the cascade spectra and pair distributions. For most observer angles, the pair synchrotron and split-photon spectra dominate the RICS primary spectra and produce complex polarization signals. In particular, the synchrotron spectra are highly polarized with degree 40%–80%, are softer than the RICS spectra, and may account for the high polarization of some magnetar spectra observed by the Imaging X-ray Polarimetry Explorer above 3 keV.

Keywords: Neutron stars
The Rise of the Galactic Empire: Ultraviolet Luminosity Functions at z ∼ 17 and z ∼ 25 Estimated with the MIDIS+NGDEEP Ultra-deep JWST/NIRCam Data Set. We present a sample of six F200W and three F277W dropout sources identified as 16 &lt; z &lt; 25 galaxy candidates using the deepest JWST/NIRCam data to date (5σ depths ∼31.5 mag at ≥2 μm), provided by the MIRI Deep Imaging Survey and the Next Generation Deep Extragalactic Exploratory Public survey. We estimate ultraviolet (UV) luminosity functions and densities at z ∼ 17 and z ∼ 25. The number density of galaxies with absolute magnitudes of ‑19 &lt; MUV &lt; ‑18 at z ∼ 17 (z ∼ 25) is a factor of 4 (25) smaller than at z ∼ 12; the luminosity density presents a similar evolution. Compared to state-of-the-art galaxy simulations, we find the need for an enhanced UV-photon production at z = 17–25 in MDM = 108.5‑9.5 M⊙ dark matter halos, provided by an increase in the star formation efficiency at early times and/or by intense compact starbursts with enhanced emissivity linked to strong burstiness, low or primordial gas metallicities, and/or a top-heavy initial mass function. There are a few robust theoretical predictions for the evolution of galaxies above z ∼ 20 in the literature; however, the continuing rapid drop in the halo mass function would predict a more rapid evolution than we observe if photon production efficiencies remained constant. Our z &gt; 16 candidates present mass-weighted ages around 30 Myr, and attenuations A(V) &lt; 0.1 mag. Their average stellar mass is M⋆ ∼ 107 M⊙, implying a stellar-to-baryon mass fraction around 10% if the emissivity increases with redshift, or significantly higher otherwise. Three candidates present very blue UV spectral slopes (β ∼ ‑3) compatible with Population III young (≲10 Myr) stars and/or high escape fractions of ionizing photons; the rest have β ∼ ‑2.5 similar to the z = 10–12 samples.

Keywords: Early universe, Galaxy formation, James Webb Space Telescope, Galaxy evolution, Broad band photometry, High-redshift galaxies
The Spectra of a Radiative Reprocessing Outflow Model for Fast Blue Optical Transients. The radiation reprocessing model, in which an optically thick outflow absorbs the high-energy emission from a central source and reemits in longer wavelengths, has been frequently invoked to explain some optically bright transients, such as fast blue optical transients (FBOTs), whose progenitor and explosion mechanism are still unknown. Previous studies on this model did not take into account the frequency dependence of the opacity. We study the radiative reprocessing and calculate the UV-optical-near-infrared (NIR) band spectra from a spherical outflow composed of pure hydrogen gas, for a time-dependent outflowing mass rate. Electron scattering and frequency-dependent bound–free and free–free opacities are considered. The spectrum deviates from the blackbody at NIR and UV frequencies; in particular, it has νLν ∝ ν1.5 at NIR frequencies, because at these frequencies the absorption optical depth from the outflow's outer edge to the so-called photon trapping radius is large and is frequency dependent. We apply our model to the prototype FBOT AT2018cow by fitting the spectra to the observed spectral energy distribution. The best-fit mass-loss rate suggests that the total outflow mass in AT2018cow is  Mout≈5.7‑0.4+0.4M⊙ . If that equals the total mass lost during an explosion, and if the progenitor is a blue supergiant (with a preexplosion mass of ∼20 M⊙), then it will suggest that the central compact remnant mass is at least ≈14 M⊙. This would imply that the central remnant is a black hole.

Keywords: Spectral energy distribution, Transient sources, High energy astrophysics
Observations of the Fluctuations in the Interplanetary Magnetic Field around L1 Point during the Solar Transient Events of 2024 with MAG Payload on board Aditya-L1 Spacecraft. The magnetometer (MAG) payload on board India's first solar mission, Aditya-L1, is a dual-sensor fluxgate magnetometer designed to measure the interplanetary magnetic field (IMF) while operating in a halo orbit around the first Sun–Earth Lagrangian point (L1). Since becoming operational in 2024 January, MAG has continuously recorded local magnetic field data and has captured several solar transient events over the past 1 yr. During these events, the IMF, typically around 5 nT, exhibited significant enhancements in magnitude. This study focuses on three such solar events observed in 2024 March, May, and October. Analysis of the magnetic field power spectra during these events reveals fluctuations consistent with Kolmogorov-type turbulence, characterized by a spectral slope close to ‑5/3. To emphasize changes in spectral behavior, the event-day spectra are compared with those from a day when the quiet solar wind conditions prevail. A marked contrast is observed: while the quiet periods exhibit anisotropic turbulence, the extreme events display quasi-isotropic behavior, with spectral slopes closely following the Kolmogorov spectrum across all three IMF components. The results, including detailed variations in spectral slope and turbulence characteristics, are presented and discussed in this paper.

Keywords: Magnetic fields
The Close Binary Properties of Massive Stars across Different Environments within the LMC. We analyze 4859 O stars in the third phase of the Optical Gravitational Lensing Experiment photometric survey of the LMC, including 415 eclipsing binaries (EBs). After accounting for the geometrical probability of eclipses, the period distribution of O-type binaries across P = 2.5─200 days follows a power law flogP ∝ (logP)Π with Π = −0.34 ± 0.06, which is skewed toward shorter periods compared to Opik's law (Π = 0). We divide our O stars into seven environments based on their clustering with B stars and other O stars. The EB fraction of O stars in young clusters is 10.2% ± 0.6%, which matches the 10.8% ± 2.1% for O stars in young Milky Way clusters. O stars in old clusters exhibit a lower EB fraction of 5.5% ± 0.9% due to the effects of binary evolution. O stars in young dense clusters, young sparse associations, and even low-mass clusters that formed in situ in the field have similar EB fractions. This uniformity suggests that the formation of close massive binaries depends on small-scale gas physics, e.g., fragmentation and migration within protostellar disks, whereas N-body interactions that scale with cluster density do not affect the close binary properties of massive stars that remain in clusters. Conversely, ejected O stars in the field exhibit a lower close binary fraction. The EB fractions of field walkaways (projected velocities vproj &lt; 24.5 km s−1) and field runaways (vproj &gt; 24.5 km s−1) are 7.3% ± 1.0% and 4.7% ± 1.0%, respectively. These values suggest that most field O stars were dynamically ejected via N-body interactions from their birth clusters, whereas field O stars that formed in situ or were kicked from supernova explosions in binaries contribute 17% and &lt;28%, respectively, to the field population.

Keywords: O stars, Close binary stars, Massive stars, Field stars, Eclipsing binary stars, Star clusters
Active Galactic Nuclei in the Extremely Overdense Galaxy Region BOSS 1441: A Chandra Observation. We present a Chandra/ACIS-I study of X-ray sources in BOSS 1441, a protocluster at z = 2.32 ± 0.02 that exhibits a prominent overdensity of Lyα emitters (LAEs). Using a 45 ks observation, we identify seven X-ray sources spatially coincident with LAE density peaks. The average X-ray photon index for the seven sources, derived from an absorbed power-law model with Galactic absorption fixed, is 1.49 (ranging from −0.68 to 2.51), corresponding to an average luminosity of 6.85 × 1044erg s−1 in the rest-frame 2─33 keV band, with individual luminosities spanning (3.57─13.96) × 1044 erg s−1. Three sources exhibit relatively flat spectral slopes. Two are associated with the MAMMOTH-1 nebula, while the third, located at the edge of BOSS 1441 with a  &gt;5'  offset from the LAE density peak, resides in a region with a high submillimeter-band density. We estimate the fraction of X-ray-detected active galactic nuclei (AGNs) among the LAEs to be  11.5−4.6+3.8% , approximately double that of previously studied LAEs. This elevated fraction suggests BOSS 1441 is in a mature evolutionary stage, with even higher AGN fractions expected in massive LAEs such as PKS 1138-262. In contrast, the submillimeter galaxy population shows a lower AGN fraction ( 6.9−4.5+6.9% ), consistent with their typically obscured nature. These results indicate that the protocluster's massive galaxies are evolving into the bright red sequence galaxies observed in local clusters, where AGNs likely play a critical role in quenching their star formation.

Keywords: Lyman-alpha galaxies, Protoclusters, X-ray active galactic nuclei
The Kinematical Behavior of Solar Eruptive Filaments Affected by the Poloidal Magnetic Field. Kinematics of solar eruptive filaments is one of the important diagnostic parameters for predicting whether solar eruptions would induce geomagnetic storms. Particularly, some geomagnetic storms might be induced by solar filament eruptions originating from unexpected surface source regions because of nonradial ejection. The nonradial ejection of filaments has received widespread attention but remains inconclusive. We select two eruptive filaments, both of which are supported by flux ropes, as indicated by the hot channel structures seen in the 94 Å images and the hook-shaped brightenings where the filament material falls back. We measure the three-dimensional ejection trajectory of the eruptive filaments by integrating the simultaneous observations from the Solar Dynamics Observatory (SDO) and Solar Terrestrial Relations Observatory (STEREO). Furthermore, we calculate the distribution of the poloidal field along the ejection path and compare it to the ejection acceleration. It is revealed that the reinforcement of the poloidal magnetic field may lead to the suppression of the acceleration, with the acceleration resuming its increase only when the poloidal field diminishes to a certain level. Additionally, we compute the spatial distribution of the poloidal field in various directions and find that the poloidal magnetic field above the filaments is asymmetric. For both investigated events, the filaments appear to eject toward the side where the poloidal magnetic field is weaker, indicating that the eruptive filaments tend to propagate along the side with weaker strapping force. This may provide a new explanation for the inclined ejection of filaments.

Keywords: Solar flares, Solar filaments, Solar magnetic fields, Solar coronal mass ejections, Solar filament eruptions
C3PO. V. Comoving Pairs Indicate Rotational Spin-down Drives the Main-sequence Li-Dip. The lithium-dip observed in mid-F dwarfs remains a long-standing challenge for stellar evolution models. We present high-precision stellar parameters and A(Li) for 22 new comoving pairs, primarily located on the hotter side of the Li-Dip. Combined with pairs from the C3PO catalog, our sample includes 124 stars with Teff between 6000 and 7300 K, encompassing and extending slightly beyond the Li-Dip. Among them, 49 comoving pairs (98 stars) have both components within the temperature range of interest. Using this expanded set of comoving pairs observed with high-resolution spectroscopy, we show that rotational spin down is the dominant process responsible for Li depletion in the Li-Dip. First, within comoving pairs, the star with v sin i &gt; 12 km s−1 shows higher A(Li) than its more slowly rotating companion within the Li-Dip, indicating that rotation-dependent mixing drives lithium depletion. Second, we observe a correlation between A(Li) and v sin i: fast rotators retain higher A(Li) with less scatter, while slow rotators show lower A(Li) and greater dispersion. Third, among slow rotators, A(Li) varies widely, suggesting that differences in initial rotation rates and spin-down histories influence how much Li is depleted. Some stars may have formed as fast rotators and spun down rapidly, leading to more Li depletion, while others may have started as slow rotators and retained more of their initial Li. These results demonstrate that rotational induced mixing plays an important role in shaping the Li-Dip beyond the effects of stellar age and mass.

Keywords: Observational astronomy, High resolution spectroscopy, Chemical abundances, Wide binary stars, Stellar evolution
Magneto-thermal Coupling and Coronal Heating in Solar Active Regions Inferred from Microwave Observations. The solar corona is much hotter than the photosphere and chromosphere, but the physical mechanism responsible for heating the coronal plasma remains unidentified. The thermal microwave emission, which is produced in a strong magnetic field above sunspots, is a promising but barely exploited tool for studying the coronal magnetic field and plasma. We analyzed the microwave observations of eight solar active regions obtained with the Siberian Radioheliograph in the years 2022─2024 in the frequency range of 6─12 GHz. We produced synthetic microwave images based on various coronal heating models, and determined the model parameters that provided the best agreement with the observations. The observations and simulations strongly favor either a steady-state (continuous) plasma heating process or high-frequency heating by small energy release events with a short cadence. The average magnetic field strength in a coronal loop was found to decrease with the loop length, following a scaling law with the most probable index of about −0.55. In the majority of cases, the estimated volumetric heating rate was weakly dependent on the magnetic field strength and decreased with the coronal loop length following a scaling law with an index of about −2.5. Among the known theoretical heating mechanisms, the model based on wave transmission or reflection in coronal loops acting as resonance cavities was found to provide the best agreement with the observations. The obtained results did not demonstrate a significant dependence on the emission frequency in the considered range.

Keywords: Solar coronal radio emission, Solar active regions, Solar coronal heating, Astronomy data modeling
Properties of Turbulent Convection and Large-scale Flows in a Rotating F-type Star Revealed by 3D Realistic Radiative Hydrodynamic Simulations. The nonlinear coupling between stellar convection and rotation is of great interest because it relates to understanding both stellar evolution and activity. We investigate the influence of rotation and the Coriolis force on the dynamics and thermodynamic structure of an F-type main-sequence star with a shallow outer convection zone. We perform a series of 3D radiative hydrodynamic simulations of a 1.47M⊙ star for different rotation rates (periods of rotation 1 and 14 days) and with local computational domains (102.4 Mm × 102.4 Mm × 50.6 Mm) placed at latitudes of 0° (equator), 30°, and 60°, using the f-plane approximation. Because the star has a relatively shallow convection zone (28.5 Mm thick or about 3% R*), we model its dynamics from the upper layers of the radiative zone, the whole convection zone, and the low atmosphere. The initial simulation results indicate that rotation suppresses temperature and density perturbations in the upper convection zone, leading to a decrease in the mean temperature throughout the convection zone. In addition to the multiscale granular-type convection, the simulations reveal the formation of roll-like patterns, the circulation in which is responsible for the retrograde flows extending from the photosphere to the bottom of the convection zone, where the mean flows transition to prograde motions with the onset of solid body rotation in the radiative zone, forming the tachocline in the overshooting layer. In this paper, we primarily discuss the properties of the outer convection zone for different rotation rates. A detailed analysis of the properties of the tachocline, the overshoot layer, as well as the properties of acoustic and gravity waves, will be discussed in follow-up papers.

Keywords: Hydrodynamical simulations, Stellar rotation, Radiative transfer simulations, Stellar convective zones
Metal-poor Star-forming Clumps in Cosmic Noon Galaxies: Evidence for Gas Inflow and Chemical Dilution Using JWST NIRISS. The formation and evolution of galaxies are intricately linked to the baryon cycle, which fuels star formation while shaping chemical abundances within galaxies. Investigating the relationship between star formation and metallicity for large samples of galaxies requires expensive IFU surveys or sophisticated tools to analyze grism data. Here we analyze JWST NIRISS slitless grism data using SLEUTH, a tool that forward models and infers spatially resolved physical properties from grism data, including observations from JWST NIRISS/NIRCam and future grism data like that from the Roman Space Telescope. SLEUTH enables the extraction of high-quality emission line maps from slitless spectra, overcoming contamination and spatially varying stellar populations, which previously limited such studies. Utilizing SLEUTH with data from the Canadian NIRISS Unbiased Cluster Survey, we investigated the relationship between metallicity and star formation in the star-forming clumps of galaxies at 0.6 &lt; z &lt; 1.35. We analyzed a sample of 20 galaxies, extracted high-quality emission line maps with SLEUTH, and analyzed, in detail, the spatially resolved properties of star-forming clumps. Using Hα, [S II], and [S III] emission line maps, we examined the spatially resolved metallicities, ionization, and star formation rates of our sample. Our findings reveal that these star-forming clumps show lower metallicities (∼0.1 dex) than their surrounding galactic environments, indicating a metallicity dilution of 20% within the clumps' gas. Our analysis indicates that these clumps exhibit intensified star formation and reduced metallicity, likely due to the inflow of metal-poor gas. These clumps illustrate the dynamic relationship between star formation and chemical enrichment within galaxies.

Keywords: Chemical enrichment, Field galaxies, Galaxy abundances
The BINGO/ABDUS Project: Forecast for Cosmological Parameters from a Mock Fast Radio Burst Survey. There are various surveys that will provide excellent data to search for and localize fast radio bursts (FRBs). The BINGO project will be one such survey, and this collaboration has already estimated an FRB detection rate that the project will yield. We present a forecast of the future constraints on our current cosmological model that the BINGO FRB detections and localizations will have when added to other current cosmological data sets. We quantify the dispersion measure (DM) as a function of redshift (z) for the BINGO FRB mock sample. Furthermore, we use current data sets (supernova, baryonic acoustic oscillation, and cosmic microwave background data) prior to assessing the efficacy of constraining dark energy models using Monte Carlo methods. Our results show that a spatially localized BINGO FRB data set will provide promising constraints on the population of host galaxies' intrinsic DM and be able to measure the nuisance parameters present within an FRB cosmological analysis. They will also provide alternative estimates on other parameters such as the Hubble constant and the dark energy equation of state. In particular, we should see that BINGO FRB data can put constraints on the degenerate w ‑ H0 plane, which the cosmic microwave background is incapable of measuring, allowing FRBs to be a viable alternative to baryonic acoustic oscillation to constrain the dark energy equation of state. We conclude that FRBs remain a promising future probe for cosmology and that the FRBs localized by the BINGO project will contribute significantly to our knowledge of the current cosmological model.

Keywords: Cosmological models, Dark energy, Cosmological parameters
Resolution-corrected White Dwarf Gravitational Redshifts Validate Fifth-generation Sloan Digital Sky Survey Wavelength Calibration and Enable Accurate Mass─Radius Tests. Leveraging the large sample size of low-resolution spectroscopic surveys to constrain white dwarf stellar structure requires an accurate understanding of the shapes of hydrogen absorption lines, which are pressure broadened by the Stark effect. Using data from both the Sloan Digital Sky Survey (SDSS) and the Type Ia Supernova Progenitor Survey, we show that substantial biases (5─15 km s−1) exist in radial velocity measurements made from observations at low spectral resolution relative to similar measurements from high-resolution spectra. Our results indicate that the physics of line formation in high-density plasmas, especially in the wings of the lines, are not fully accounted for in state-of-the-art white dwarf model atmospheres. We provide corrections to account for these resolution-induced redshifts in a way that is independent of an assumed mass─radius relation, and we demonstrate that statistical measurements of gravitational redshift with these corrections yield improved agreement with theoretical mass─radius relations. Our results provide a set of best practices for white dwarf radial velocity measurements from low-resolution spectroscopy, including those from SDSS, the Dark Energy Spectroscopic Instrument, the 4 m Multi-Object Spectroscopic Telescope, and the Wide-Field Multiplexed Spectroscopic Facility.

Keywords: White dwarf stars, Stellar spectral lines, Degenerate matter