Sazuna/UAT_keywords huggingface dataset:
Meridional Circulation. II. A Unified Mechanism for Lithium Depletion in Solar Analogs and the Lithium Dip in Mid-F Cluster Stars. The behavior of lithium (Li) in Population I main-sequence stars challenges standard stellar theory. Two phenomena stand out: the solar Li problem, which extends to Li depletion in solar analogs, and the Li dip observed in mid-F stars within open clusters. Building on the meridional-circulation-driven radial mixing framework previously developed to explain Li-enriched red clump stars, we explore its relevance to Li depletion on the main sequence. First, our models reproduce the observed A(Li)–age correlation in solar analogs. Through detailed isochrone analysis, we find good agreement between the simulated and observed A(Li)–Teff relationships within the solar analog parameter space. However, the predicted solar Li abundance (∼1.5 dex) is still higher than current solar measurements. Second, our models partially explain the Li dip phenomenon in mid-F cluster stars. The models accurately reproduce Li distributions on the cool side of the Li dip in most clusters and capture the Li behaviors on the hot side observed in systems like the Hyades. However, we identify limitations in the models' ability to fully reproduce the dip morphology, particularly due to the rotation velocity distribution of sample stars in this temperature zone.

Keywords: Solar analogs, Stellar abundances, Lithium stars, Low mass stars, Main sequence stars, Open star clusters, Stellar rotation, Population I stars, Stellar evolution
Investigating Multiband Variability Characteristics of the Typical BLSy1 Mrk 1220 through Intensive Swift Monitoring. Broad-line Seyfert 1 galaxies (BLSy1s), characterized by high black hole masses and low accretion rates, represent a crucial subclass of active galactic nuclei. We present a systematic analysis of the variability and X-ray spectral properties of the BLSy1 Mrk 1220 using 225 high-quality Swift observations from 2016 to 2018. Mrk 1220 exhibits significant multiwavelength variability across X-ray, ultraviolet (UV), and optical bands, with amplitude increasing with energy but remaining weaker than narrow-line Seyfert 1 galaxies (NLSy1s) with high accretion rates. Cross-correlation analysis reveals no significant interband time delays. The UV/optical–X-ray correlation weakens with increasing wavelength, with a maximum correlation coefficient of only 0.54. The relatively weak UV/X-ray connection may be attributed to the dynamic evolution of the coronal structure. Structure function (SF) analysis reveals a distinctive double "S" structure in optical/UV bands. Short-timescale SF parameters resemble those of NLSy1s, while X-ray bands show significantly longer decorrelation timescales, indicating an extended X-ray corona. SF spectral coefficients (β) across bands generally follow the damped random walk model, with only the U-band long-timescale β slightly elevated, potentially influenced by broad-line region radiation. X-ray spectral characteristics remain consistent between high and low flux states, showing weak soft excess below 1 keV. The stability of the soft excess parameters and power-law spectral index suggests unchanged coronal geometry across states, with X-ray variations primarily driven by intrinsic electron density fluctuations. These results provide valuable observational constraints for understanding the variability mechanisms and spectral characteristics of typical BLSy1s.

Keywords: Seyfert galaxies, X-ray active galactic nuclei, Time domain astronomy
Blue Supergiants in the Pinwheel Galaxy M101: Comparison with H II Region Chemical Abundances, Spectroscopic Distance, and an Independent Determination of the Hubble Constant. We present a quantitative spectroscopic study of 13 blue supergiant stars in the Pinwheel Galaxy M101, based on data obtained with the Low Resolution Imaging Spectrometer available at the Keck I telescope. The average stellar metallicity decreases from ∼1.9 Z⊙ near the center of the galaxy to ∼0.3 Z⊙ at the optical outskirts. The galactocentric radial metallicity gradient is statistically consistent with previous studies of the gas-phase oxygen abundance from H II regions using the direct method. The H II region-based Cepheid metallicities used by A. G. Riess et al. in their determination of the Hubble constant H0 are in substantial agreement with our measurements. The direct method gas-phase metallicities of the 18 star-forming galaxies we have analyzed so far, when adjusted upward for a mean ∼0.15 dex oxygen dust depletion factor, are in good agreement with those we infer from the supergiants, over a factor of 50 in metallicity. From the same data, we derive an expression for the metal-dependent depletion of oxygen in photoionized nebulae. Utilizing the flux-weighted gravity─luminosity relationship (FGLR) of blue supergiants, we measure a distance to M101, D = 6.5 ± 0.2 Mpc (μ = 29.06 ± 0.08), which is within 1σ from determinations based on the tip of the red giant branch and Cepheids. With M101 as a nearby Type Ia supernova host and using the observed standardized B-band magnitude of the supernova, our FGLR distance yields an independent value of H0 = 72.5 ± 4.6 km s−1 Mpc−1.

Keywords: Stellar abundances, Galaxy stellar content, Chemical abundances, Hubble constant, Galaxy abundances, Spectroscopy, Supergiant stars, Stellar distance
The Wrath of KAN: Enabling Fast, Accurate, and Transparent Emulation of the Global 21 cm Cosmology Signal. Based on the Kolmogorov─Arnold network (KAN), we present a novel emulator of the global 21 cm cosmology signal, 21CMKAN, that provides extremely fast training speed while achieving nearly equivalent accuracy to the most accurate emulator to date, 21CMLSTM. The combination of enhanced speed and accuracy facilitated by 21CMKAN enables rapid and highly accurate physical parameter estimation analyses of multiple 21 cm models, which is needed to fully characterize the complex feature space across models and produce robust constraints on the early Universe. Rather than using static functions to model complex relationships like traditional fully connected neural networks do, KANs learn expressive transformations that can perform significantly better for low-dimensional physical problems. 21CMKAN predicts a given signal for two well-known models in the community in 3.7 ms on average and trains about 75 times faster than 21CMLSTM, when utilizing the same typical GPU. In addition, 21CMKAN is able to achieve these speeds because of its learnable, data-driven transformations and its relatively small number of trainable parameters compared to a memory-based emulator. We show that 21CMKAN required less than 30 minutes to train and fit these simulated signals and obtain unbiased posterior distributions. We find that the transparent architecture of 21CMKAN allows us to conveniently interpret and further validate its emulation results in terms of the sensitivity of the 21 cm signal to each physical parameter. This work demonstrates the effectiveness of KANs and their ability to more quickly and accurately mimic expensive physical simulations in comparison to other types of neural networks.

Keywords: Cosmology, Early universe, Astronomy software, Neural networks, Posterior distribution, Nested sampling
A Monte Carlo Simulation on the Scattering Coefficients of Solar Radio Wave Propagation. Radio waves undergo scattering by small-scale density fluctuations during propagation through the solar-terrestrial environment, substantially affecting the observed characteristics of solar radio bursts. This scattering process can be effectively modeled as photon diffusion in phase space. In this study, we present a comprehensive comparison between the quasilinear diffusion coefficients and those calculated by ray-tracing the photon trajectories in numerically generated, broadband, isotropic density fluctuation fields in both 2D and 3D configurations. The comparative analysis demonstrates that for weak scattering, the simulated diffusion coefficients agree well with the quasilinear theoretical predictions. However, when the radio frequency approaches the electron plasma frequency and/or the density fluctuation amplitude becomes significant, photons experience strong scattering. Under such conditions, the quasilinear theory tends to underestimate the scattering strength of photons induced by 2D density fluctuations while overestimating the scattering strength in 3D cases. Furthermore, we implement a group velocity correction to the theoretical diffusion coefficients, based on the effective propagation speed averaged over all test photons. The corrected coefficients provide an accurate quantification of the scattering strength for radio waves propagating through 3D density fluctuations. The physical mechanisms underlying these phenomena are elucidated in the discussion.

Keywords: Monte Carlo methods, Radio bursts, Solar radio emission
Planetary Nebulae in the eROSITA eRASS1 Catalog. Some planetary nebulae (PNs) host X-ray-emitting hot bubbles shaped by stellar wind interactions and/or harbor X-ray-emitting central stars due to accretion, shocks within their fast stellar winds, or even chromospheric emission from binary companions. In both cases, the properties of the X-ray emission critically probe late stages of stellar evolution for such low- and intermediate-mass stars. While extant Chandra and XMM-Newton observations have detected X-ray emission in PNs, the numbers known remain very small (∼40) compared to the overall Galactic PNs population (∼4000). We have initiated a project aimed at increasing the sample of known PNs with X-ray emission using both current and new space-based X-ray telescopes, such as the Einstein probe. To further investigate their X-ray properties to elucidate what drives current X-ray PN detections, we have cross-searched the SRG eROSITA-DE eRASS1 source catalog and the Hong Kong (HASH) PNs Database. Five known X-ray PNs have been detected (A30, NGC 2392, NGC 3242, NGC 5315, and LoTr 5), two new X-ray PNs are revealed (IC 1297 and NGC 2867), one (K 1–27) is removed from previous X-ray compilations, and another 11 previously detected X-ray emitting PNs are not recovered. A comparison of the X-ray flux of detected and undetected X-ray PNs reveals that eROSITA eRASS1 is sensitive to PNs with X-ray fluxes larger than ≈2 × 10‑14 erg cm‑2 s‑1. The frequency of occurrence is ≃0.5% among the 1430 HASH True PNs in the eRASS1 footprint.

Keywords: High energy astrophysics, Stellar astronomy, Planetary nebulae, Interstellar medium
Statistical Properties of a Polarization Vector's Ellipticity Angle. The orientation of a polarization vector on the Poincaré sphere is defined by its position angle (PA) and ellipticity angle (EA). The radio emission from pulsars, magnetars, and fast radio bursts can be elliptically polarized, and measurements of the EA have become increasingly important in interpretations and models of their polarization. An in-depth understanding of the statistical properties of the measured polarization angles is a prerequisite to their detailed interpretation. While the statistics of the PA have been understood for some time, the statistics of the EA do not appear to be as well developed as those of the PA. The statistical properties of the EA are derived when the amplitude of the polarization vector is constant, to include its probability density, mean, standard deviation, and confidence limits. Similar to the PA, the standard deviation and confidence limits of the EA vary inversely with the polarization signal-to-noise ratio. However, unlike the PA, the probability density of the EA is generally asymmetric, its standard deviation and confidence limits are dependent upon the intrinsic value of the EA, and the measured EA is biased by the instrumental noise, particularly at low signal-to-noise ratios and large values of the intrinsic EA. General expressions for the joint probability density of the polarization angles and the probability density of the EA are also derived when the amplitude of the polarization vector fluctuates due to the superposition of incoherent modes of orthogonal polarization.

Keywords: Astrostatistics distributions, Astrostatistics techniques, Radio transient sources, Radio pulsars
Parallel Alignments between Magnetic Fields and Dense Structures in the Central Molecular Zone. The recent Far-Infrared Polarimetric Large-Area Central Molecular Zone Exploration (FIREPLACE) survey with SOFIA has mapped plane-of-sky magnetic field orientations within the Central Molecular Zone (CMZ) of the Milky Way. Applying the Histogram of Relative Orientations analysis to the FIREPLACE data, we find that the relative orientation between magnetic fields and column density structures is random in low-density regions ( 2×1022≲NH2≲1023cm−2 ) but becomes preferentially parallel in high-density regions (≳1023 cm−2). This trend is in contrast with that of the nearby molecular clouds, where the relative orientation transitions from parallel to perpendicular with increasing column densities. However, the relative orientation varies between individual CMZ clouds. Comparisons with magnetohydrodynamic simulations specific to the CMZ conditions suggest that the observed parallel alignment is intrinsic, rather than artifacts caused by the projection effect. The origin of this parallel configuration may arise from the fact that most dense structures in the CMZ are not self-gravitating, as they are in supervirial states, except for the ministarburst region Sgr B2. These findings are consistent with the low star formation efficiency observed in the CMZ compared to that in the Galactic disk.

Keywords: Galactic center, Magnetic fields, Interstellar medium
Gone with the Wind: JWST-MIRI Unveils a Strong Outflow from the Quiescent Stellar-mass Black Hole A0620-00. We present new observations of the black hole X-ray binary A0620-00 using the Mid-Infrared (MIR) Instrument on the James Webb Space Telescope, during a state where the X-ray luminosity is 9 orders of magnitude below Eddington, and coordinated with radio, near-infrared, and optical observations. The goal is to understand the nature of the excess MIR emission originally detected by Spitzer redward of 8 μm. The stellar-subtracted MIR spectrum is well modeled by a power law with a spectral index of α = 0.72 ± 0.01, where the flux density scales with frequency as Fν ∝ να. The spectral characteristics, along with rapid variability—a 40% flux flare at 15 μm and 25% achromatic variability in the 5─12 μm range—rule out a circumbinary disk as the source of the MIR excess. The Low Resolution Spectrometer reveals a prominent emission feature at 7.5 μm, resulting from the blend of three hydrogen recombination lines. While the contribution from partially self-absorbed synchrotron radiation cannot be ruled out, we argue that thermal bremsstrahlung from a warm (a few tens of thousands of Kelvin) wind accounts for the MIR excess; the same outflow is responsible for the emission lines. The inferred mass outflow rate indicates that the system's low luminosity is due to a substantial fraction of the mass supplied by the donor star being expelled through a wind rather than accreted onto the black hole.

Keywords: Infrared excess, Low-mass x-ray binary stars, Stellar mass black holes, High energy astrophysics
Can a Hybrid Star with Constant Sound Speed Parameterization Explain the New NICER Mass–Radius Measurements?. We present a reanalysis of Neutron Star Interior Composition Explorer observations of PSR J0740+6620 and PSR J0030+0451 in order to test the consistency of various nuclear equations of state (EoSs) within the framework of hybrid star models. In particular, we examine how different surface temperature models for PSR J0030+0451, categorized as scenarios A, B, and C, lead to significantly different mass–radius estimates. We present a comprehensive study constraining the parameters of the constant speed of sound (CSS) model based on representative observational categories. Our findings indicate that for certain hadronic EoSs (for representative cases, we chose one density-independent and one density-dependent), the results remain consistent for lower values of the energy density discontinuity, but discrepancies emerge as the discontinuity increases. Scenarios involving large jumps in energy density are generally disfavored by the requirement of supporting massive neutron stars, while higher values of the speed of sound in the quark matter phase tend to yield better agreement with various observational trends. These results underscore the importance of phase transition characteristics in aligning hybrid star models with current astrophysical observations. We have also constrained the CSS parameters using observational data from PSR J0740+6620 and PSR J0952–0607 by computing the maximum mass supported by these parameters.

Keywords: Neutron stars, Nuclear astrophysics, Compact objects
Effects of Crystal Orientation and Temperature on Space Irradiation of Silicates. Space irradiation plays a crucial role in surface weathering and hydration processes of airless bodies in the solar system. Despite extensive laboratory studies, the impact of crystal orientation and temperature on these irradiation processes remains poorly understood. In this study, we conducted hydrogen-implantation experiments on olivine crystals, controlling both crystal orientation and temperature. Our results reveal that the amount and depth of implanted hydrogen depend on the crystal orientation. Olivine exhibits the largest resistance to ion irradiation along the [100] direction, resulting in a thinner damaged region (∼180–200 nm) and subsurface vesicle formation. In contrast, the [010] and [001] orientations allow deeper damage (∼200–210 nm) accompanied by fracturing. Additionally, increasing temperatures from 25°C to 200°C promote the saturation and retention of implanted hydrogen. However, above a critical temperature (∼200°C for olivine), hydrogen levels stabilize, and no further increase is observed. These findings highlight the critical role of crystal orientation and temperature in the irradiation process, providing important constraints for numerical models simulating the effects of space irradiation on rocky bodies.

Keywords: Space plasmas, Mineral physics, Laboratory astrophysics, Solar system
Early Evolution of the Cavity and Core of a Coronal Mass Ejection in the Inner Corona. Coronal mass ejections (CMEs) typically exhibit a three-component structure in white-light (WL) coronagraphs. Utilizing the seamless observations of the inner corona (≤3 R⊙), we have revealed the early evolution of the cavity and core of a CME starting at ∼18:20 UT on 2014 October 14. The CME originates from a hot channel (HC), which appears as the bright core and compresses the cavity in WL images. Specifically, most of the dark cavity in WL is filled by bright loop-like structures in 174 Å. The differential emission measure analysis indicates that the electron temperature decreases from the core (∼13.4 MK) to the cavity (∼1.35 MK), and the CME cavity is significantly cooler than that enshrouding a prominence (≥2 MK). The effective temperature of the cavity increases over time in general, probably due to the compression by the HC expansion. The evolution of the CME bright core includes slow-rise, fast-rise (up to ∼330 km s‑1), and residual-acceleration phases. The cavity exhibits an evolution similar to the core but lags by ∼4 minutes, with a lower speed peaking at ∼220 km s‑1. Moreover, the 2D radial speed distribution exhibits the highest speeds at the core apex. The kinematical results further confirm the compression of the cavity. The present event supports the new explanation of the CME structures, i.e., the magnetic flux rope (MFR), which is proxied by the HC, is only responsible for the core, while the cavity is likely a low-density region between the CME front and the MFR.

Keywords: Solar activity, The Sun, Astronomy data analysis, Solar coronal mass ejections
Evolution of LISA Observables for Binary Black Holes Lensed by a Supermassive Black Hole. Binary black holes (BBHs) are expected to form and merge in active galactic nuclei (AGN), deep in the potential well of a supermassive black hole (SMBH), from populations that exist in a nuclear star cluster. Here we investigate the gravitational-wave (GW) signature of a BBH lensed by a nearby SMBH. For a fiducial GW150914-like BBH orbiting close to a 108 M⊙ SMBH located at z = 0.1, the lensed GW signal varies in a predictable manner in and out of the Laser Interferometer Space Antenna (LISA) detectability band and across frequencies. The occurrence of such signatures has the potential to confound LISA global fit models if they are not modeled. Detection of these sources provides an independent measure of AGN inclination angles, along with detecting warping of the inner disk and measuring the SMBH spin.

Keywords: Black holes, Stellar mass black holes, Gravitational lensing, Gravitational waves, Active galactic nuclei, Star clusters
XMM-Newton View of Pulsating Iron Fluorescent Emission from Centaurus X-3. Centaurus X─3 (Cen X─3) is a bright, high-mass X-ray binary pulsar. We present a pulse phase─resolved X-ray spectral analysis of data from an archival XMM-Newton observation of Cen X─3 taken during the high state of the source. The observation was entirely in the out-of-eclipse part of the binary orbit. We study the pulse phase variability of the three Kα fluorescent emission lines from near-neutral, helium-like, and hydrogen-like iron, along with the iron Kβ emission line. All four lines show clear modulation with the pulse phase of the neutron star (NS), and modulation is found to be higher for the lines from highly ionised iron compared to the neutral lines. Structures within the light travel distance corresponding to the pulse period of the NS are likely responsible for the pulse phase modulation of the emission lines. We have also investigated the orbital phase dependence of the pulse phase variability in the iron lines by dividing the data into four segments at different orbital phases of Cen X─3. The pulse phase modulation behavior of the four lines is quite identical at different orbital phases of Cen X─3, indicating the pulsed iron emission region is persistent in nature and probably phase aligned with respect to the observer. The accretion stream intercepting the line of sight can probably produce the observed phase dependence of the iron fluorescence emission lines.

Keywords: X-ray astronomy, Neutron stars, X-ray binary stars, High mass x-ray binary stars, Binary pulsars