Sazuna/UAT_keywords huggingface dataset:
The Impact of Initial Composition on Massive Star Evolution and Nucleosynthesis. We study the sensitivity of presupernova evolution and supernova nucleosynthesis yields of massive stars to variations of the initial composition. We use the solar abundances from Lodders, and compute two different sets of initial stellar compositions: (i) scaled solar abundances and (ii) the isotopic galactic chemical history model (GCH) developed by C. West &amp; A. Heger. We run a grid of models using the KEPLER stellar evolution code, with 7 initial stellar masses, 12 initial metallicities, and the 2 scaling methods, to explore the effects on nucleosynthesis over a metallicity range of ‑4.0 ≤ [Z] ≤ +0.3. We find that the compositions from the GCH model better reproduce the weak s-process peak than the scaled solar models. The model yields are then used in the OMEGA Galactic Chemical Evolution (GCE) code to assess this result further. We find that initial abundances used in computing stellar structure have a larger impact on the GCE results than the initial abundances used in the large nuclear co-processing network, with the GCH model again being favored when compared to observations. Finally, a machine learning algorithm was used to verify the free parameter values of the GCH model, which were previously found by C. West &amp; A. Heger using a stochastic fitting process. The updated model is provided as an accessible tool for further nucleosynthesis studies.

Keywords: Isotopic abundances, Nucleosynthesis, Galaxy chemical evolution, Stellar abundances, Massive stars, Solar abundances, Galaxy abundances, Stellar nucleosynthesis, Supernovae
The Absolute Age of Milky Way Globular Clusters. Globular clusters (GCs) provide statistically significant coeval populations of stars spanning various evolutionary stages, allowing robust constraints on stellar evolution model parameters and ages. We analyze eight old Milky Way GCs with metallicities between [Fe/H] = −2.31 and −0.77 by comparing theoretical isochrone sets from the Dartmouth Stellar Evolution Program to Hubble Space Telescope (HST) observations. The theoretical isochrones include uncertainties introduced by 21 stellar evolution parameters such as convective mixing, opacity, diffusion, and nuclear reactions, capturing much of the quantifiable physics used in our code. For each isochrone, we construct simulated color─magnitude diagrams (CMDs) near the main-sequence turnoff region and apply two full-CMD-fitting methods to fit HST Advanced Camera for Surveys data across a range of distances and reddening and measure the absolute age of each GC from the resulting posterior distribution, which accounts for uncertainties in the stellar models, observations, and fitting method. The resulting best-fitting absolute ages range from ≍11.5 to 13.5 Gyr, with a typical error of 0.5─0.75 Gyr; the data show a clear trend toward older ages at lower metallicities. Notably, distance and reddening account for over 50% of the uncertainty in age determination in each case, with metallicity, α abundance, mixing length, and helium diffusion being the most important stellar physics parameters for the error budget. We also provide an absolute age─metallicity relation for Milky Way GCs.

Keywords: Cosmology, Globular star clusters, Computational astronomy, Stellar evolutionary models, Stellar physics
NuSTAR Broadband X-Ray Observation of EF Eri Following its Reawakening into a High Accretion State. We present the first NuSTAR X-ray observation of EF Eri, a well-known polar system. The NuSTAR observation was conducted in conjunction with NICER shortly after EF Eri entered a high accretion state following an unprecedented period of low activity lasting 26 yr since 1997. NuSTAR detected hard X-ray emission up to 50 keV with an X-ray flux of 1.2 × 10‑10 erg s‑1 cm‑2 (3–50 keV). Folded X-ray lightcurves exhibit a single peak with ∼65% spin modulation throughout the 3–50 keV band. We found no evidence of quasiperiodic oscillation (QPO) signals at ν = 0.1–100 Hz with an upper limit on the QPO amplitude below 5% (90% confidence limit) at ν ∼ 0.5 Hz where the optical QPO was previously detected. Our 1D accretion column model, called MCVSPEC, was fitted to the NuSTAR spectral data, yielding an accurate white dwarf (WD) mass measurement of M = (0.55–0.63) M⊙. MCVSPEC accounts for radiative cooling by thermal bremsstrahlung and cyclotron emission, X-ray reflection off the WD surface, and a previously constrained range of the accretion column area. The derived WD mass range is in excellent agreement with the previous measurement of M = (0.55–0.65) M⊙ in the optical band. This demonstrates a combination of broadband X-ray spectral analysis and the MCVSPEC model that can be employed in our ongoing NuSTAR observation campaign of other polars to determine their WD masses accurately.

Keywords: Accretion, White dwarf stars, X-ray observatories, Compact objects, Cataclysmic variable stars, AM Herculis stars
Non-LTE Synthetic Observables of a Multidimensional Model of Type Ia Supernovae. Many promising explosion models for the elusive origin of Type Ia supernovae (SNe Ia) ultimately fail to completely reproduce a number of observed properties of these events. One limiting factor for many of these models is the use of the local thermodynamic equilibrium (LTE) assumption in the calculation of their synthetic observables, which has been shown to prevent the accurate prediction of a number of fundamental features of SNe Ia. The inclusion of high-accuracy non-LTE physics, however, increases computational cost and complexity such that multidimensional non-LTE calculations are often unfeasible, which can be problematic for models that are inherently multidimensional. In this work, we conduct radiative transfer calculations using 1D profiles that each correspond with a line of sight from an asymmetric, 2D SN Ia model. We find, in LTE, that the synthetic observables from these calculations efficiently reproduce those from the 2D calculation when an equivalence of bolometric luminosities between the 1D and 2D treatments is enforced. This allows for the accurate calculation of synthetic observables in 1D while still preserving multidimensional effects associated with the model. We leverage this to produce high-accuracy observables from 1D non-LTE calculations, showing significantly improved agreement with observations, including a roughly 50% reduction of B-band decline rate into congruence with the observed Phillips relation. Additionally, our non-LTE observables show Si IIλ5972 pEWs that are much more similar to observations, while spanning multiple Branch classes, suggesting that some spectral classifications of SNe Ia may arise from line-of-sight effects.

Keywords: Type Ia supernovae, Radiative transfer
Wave─Particle Interaction in the Upstream of Interplanetary Coronal Mass Ejection Shocks. Shocks associated with interplanetary coronal mass ejections are known to energize charged particles and give rise to solar energetic particles. Many of these energetic particles move ahead of the shock to create a foreshock region. The foreshock region primarily consists of solar wind plasma, exhibiting turbulent velocity and magnetic fields. Such turbulent behavior results from inherent solar wind turbulence modified by energetic particles. We analyze magnetic field data from six such ICME shocks observed by the Wind spacecraft. The analysis of the shock upstream shows that the magnetic power spectral density (PSD) maintains a power-law slope of −5/3. We also identify clear intermittent peaks in the PSD. After characterizing these peaks, we investigate various possibilities for their generation. Our analysis indicates that these peaks in the PSD are due to the resonant interaction of Alfvén waves with the bulk solar wind protons and protons with energy up to 10 keV. However, evidence of Alfvén wave interaction with highly energetic protons is not evident in our analysis, and we anticipate that such evidence is obscured by the prevailing solar wind turbulence in the shock upstream.

Keywords: Solar energetic particles, Solar coronal mass ejection shocks, Alfven waves, Heliosphere
Kilonova Emissions from Neutron Star Merger Remnants: Implications for the Nuclear Equation of State. Multimessenger observations of binary neutron star mergers can provide valuable information on the nuclear equation of state (EOS). Here, we investigate the extent to which electromagnetic observations of the associated kilonovae allow us to place constraints on the EOS. For this, we use state-of-the-art three-dimensional general-relativistic magnetohydrodynamics simulations and detailed nucleosynthesis modeling to connect properties of observed light curves to properties of the accretion disk, and hence, the EOS. Using our general approach, we use multimessenger observations of GW170817/AT2017gfo to study the impact of various sources of uncertainty on inferences of the EOS. We constrain the radius of a 1.4M⊙ neutron star to lie within 10.30 ≤ R1.4 ≤ 13.0 km and the maximum mass to be MTOV ≤ 3.06M⊙.

Keywords: Neutron stars, Explosive nucleosynthesis, Nucleosynthesis, R-process, Nuclear astrophysics, Compact objects
Properties of Slow Magnetoacoustic Waves Observed Simultaneously Using Hi-C 2.1 and AIA. Propagating slow magnetoacoustic waves are commonly observed in different coronal structures but are most prominent in active region fan loops. Their rapid damping with damping lengths of the order of a wavelength has been investigated in the past by several authors. Although different physical mechanisms have been proposed, significant discrepancies between the theory and observations remain. Recent high-resolution observations captured simultaneously by two different instruments reveal distinct damping lengths for slow magnetoacoustic waves, although their passbands are similar. These results suggest a possible contribution of instrumental characteristics to the measurement of damping lengths. Here, we analyze the behavior of slow waves using a different pair of instruments in order to check the prevalence of such results. In particular, the cotemporal observations of active region NOAA AR 12712 by the High-resolution Coronal Imager (Hi-C 2.1; Hi-C) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) are utilised. The estimated oscillation periods of slow magnetoacoustic waves identified from these data are 2.7 ± 0.2 minutes from SDO/AIA and 2.8 ± 1.2 minutes from Hi-C 2.1. The corresponding propagation speeds are found to be 46.0 ± 1.7 and 48.1 ± 0.6 km s‑1, respectively. Damping lengths were calculated by two different methods, the phase tracking method (PTM) and the Amplitude Tracking Method (ATM). The obtained values from the PTM are 4.0 ± 2.1 and 4.1 ± 0.3 Mm, while those from the ATM are 3.4 ± 1.0 and 3.7 ± 0.1 Mm, respectively, for the AIA and Hi-C data. Our results do not indicate any notable difference in damping lengths between these instruments.

Keywords: Active solar corona, Magnetohydrodynamics, Solar coronal waves
New Tests of the Cosmic Distance Duality Relation with DESI 2024 Baryon Acoustic Oscillation Observations. In this paper, we test the cosmic distance duality relation (CDDR), as required by the Etherington reciprocity theorem, which connects the angular diameter distance and the luminosity distance via the relation DL(z) = DA(z)(1 + z)2. Our analysis is based on the latest baryon acoustic oscillation (BAO) measurements provided by the Dark Energy Survey (DES), the Baryon Oscillation Spectroscopic Survey/Extended BOSS, and the Dark Energy Spectroscopic Instrument surveys. Specifically, an unbiased test of the CDDR is performed through a novel, model-independent method inspired by the two-point diagnostic approach, with DES-SN 5YR and Pantheon type Ia supernova (SN Ia) sample reconstructed using the Artificial Neural Network technique. This methodology effectively eliminates all nuisance parameters, including the sound horizon scale rd from BAO and the absolute magnitude MB from SN Ia. A set of N − 1 independent CDDR ratios ηij are constructed for statistical analysis. At the current observational level, no significant deviation from the CDDR is observed at low redshifts, whereas we find positive evidence (&gt;2σ confidence level) of deviation from the CDDR at two high redshifts (z = 2.33 and z = 2.334). Therefore, our results confirm that the BAO measurement provides a powerful tool to test such a fundamental relation in modern cosmology.

Keywords: Observational cosmology, Cosmological parameters
Heliospheric Current Sheet Crossings Observed by Voyager 2 across 1–33.6 au. In this study, we identified 188 heliospheric current sheet (HCS) crossing events observed by Voyager 2 between 1977 and 1990, spanning heliocentric distances from 1 to 33.6 au. The identified HCS crossings revealed well-defined trends including a &gt;30% decrease in magnetic field intensity and &gt;20% increases in proton density and temperature. The Harris sheet model fitting to all 188 HCS crossing events indicates that the estimated HCS thickness spans over 2 orders of magnitude, ranging from  7×103  to  2.5×106  km, with a median value of  3.3×105  km. For 84.6% of the events, the HCS planes lie within  ‑30°  to  30°  in latitude from the equatorial plane, whereas the others indicate highly tilted HCS planes. Similarly, for 85.6% of the events, the HCS planes align with the Parker spiral field from the Parker field direction (within 30°), whereas the others exhibit significant longitudinal tilt. Additionally, a substantial fraction of HCS crossings indicate a significant normal magnetic field component (e.g.,  Bnormal/B&gt;  0.3 for 38.8% of the total events), implying rotational discontinuities. Comparing our results with previous studies on HCS thickness from near the Sun to the heliosheath, we find a general increase in thickness with distance. Notably, at 1–33.6 au, HCS thickness remains significantly larger than the ion inertial length, implying conditions generally unfavorable for magnetic reconnection. This contrasts with recent reports of frequent reconnection at HCSs closer to the Sun. Our findings provide a comprehensive insight into the HCS structures across a wide range of heliospheric distances.

Keywords: Heliosphere
On the Very Bright Dropouts Selected Using the James Webb Space Telescope NIRCam Instrument. The selection of candidate high-redshift galaxies using the dropout technique targeting the Lyman-break signature sometimes yields very bright objects that are too luminous to be easily explained if they are indeed at the expected redshifts. Here, we present systematic study of very bright dropouts selected through successive bands of the NIRCam instrument onboard the James Webb Space Telescope (JWST). Using the public NIRCam data in four blank fields over 500 arcmin2, 300 such objects were found. They have F356W magnitudes &lt;25.1 mag or &lt;26.0 mag depending on the dropout passband, and the majority of them (&gt;80%) have very red F115W ‑ F356W colors &gt;2.0 mag, qualifying them as "extremely red objects." We focus on 137 objects that also have mid-infrared observations from the JWST MIRI instrument. Their spectral energy distribution analysis shows that these objects are dominated by low-redshift (z ∼ 1–4) galaxies (≳67%). However, a non-negligible fraction (≳7%) could be at high redshifts. Seven of our objects have secure spectroscopic redshifts from JWST NIRSpec identifications, and the results confirm this picture: while six are low-redshift galaxies (z ≈ 3), one is a known galaxy at z = 8.679 (with MUV = ‑22.4 mag and stellar mass M* = 109.1M⊙) recovered in our sample. In light of recent theoretical models on early galaxy formation, this confirmed high-redshift galaxy does not pose a challenge. However, since our sample contains very luminous high-redshift candidates in the regime still underexplored (MUV ≤ ‑23 mag and M* &gt; 1010.5M⊙), spectroscopic identifications are necessary to ensure they do not create tension with these new models.

Keywords: Starburst galaxies, High-redshift galaxies
Resolved ALMA [C II] 158 μm Observations at Cosmic Noon: Interstellar Medium Structure and Dynamics of the Starbursting QSO SDSS J1000. We present spatially resolved Atacama Large Millimeter/submillimeter Array Band 9 observations of the [C II] 158 μm fine structure line from an optically selected quasar, SDSS J100038.01+020822.4 (J1000), at z = 1.8275. By utilizing [O I] 63 μm line observations from Herschel/PACS and constructing a detailed dust spectral energy distribution using Herschel and Spitzer archival imaging data, we show that the [C II] line emission is well explained by a photodissociation region (PDR) model, in which the emission arises from the surfaces of molecular clouds exposed to far-UV radiation fields ∼5 × 103 times the local interstellar radiation field (G0). We find a factor of 30 variation in spatially resolved [C II]/far-IR continuum across the source, which is explained by the reduced fraction of cooling via [C II] line emission at such high far-UV field strengths. By matching the derived PDR parameters to the observed far-IR line and continuum intensities we derive cloud size scales and find that typical cloud radii in J1000 are ∼3.5 pc, perhaps indicating an interstellar medium that is highly fractured due to intense star formation activity. We model the galaxy dynamically and find that the [C II] emission is contained within a compact, dynamically cold disk with v/σ = 6.2, consistent with the IllustrisTNG50 cosmological simulation. We also report the discovery of a companion galaxy to J1000 confirmed by the detection of [C II] and use recently obtained JWST/NIRCam imaging of the system to argue for J1000 being an interacting system. With total stellar mass ∼ 1.5 × 1010 M⊙ and main-component dynamical mass ≳ 1011 M⊙, the J1000 system is a progenitor to the most massive galaxies seen in the local Universe.

Keywords: Galaxy dynamics, Photodissociation regions, Dust continuum emission, Interstellar medium, Galaxy spectroscopy, High-redshift galaxies
Neutrino Anisotropy as a Probe of Extreme Astrophysical Accelerators. We predict that neutrino sources following the matter distribution of the Universe result in an anisotropy in the neutrino sky imprinted by the local large-scale structure (LSS). We calculate the level of this anisotropy and explore how it depends on the cosmological evolution of neutrino sources. We show how the level of anisotropy can be amplified when a cutoff in the neutrino spectrum is considered, introducing an effective neutrino horizon. This effect might allow for future neutrino detectors to measure a neutrino anisotropy associated with the local LSS. Measurement of the level of this anisotropy along with features of the neutrino spectrum will allow observers to constrain the cosmological evolution of neutrino sources, which at ultra-high energies (UHEs) are also expected to be the sources of UHE cosmic rays.

Keywords: Neutrino astronomy, Cosmic ray sources, Ultra-high-energy cosmic radiation
NuSTAR and XMM-Newton Observations of PSR J1930+1852 and Its Pulsar Wind Nebula. Synchrotron X-ray emission from a pulsar wind nebula (PWN) is a sensitive probe of its magnetic field and high-energy particle population. Here we analyze contemporaneous NuSTAR and XMM-Newton observations of the PWN G54.1+0.3, powered by pulsar PSR J1930+1852. We also present a preliminary timing analysis of the central pulsar PSR J1930+1852 and analyze its X-ray pulse profiles in different energy bands. We detect X-ray emission from the combined pulsar and PWN system up to ≈70 keV, while emission from the PWN itself has been detected up to ≈30 keV, with a photon index Γ increasing from ∼1.9 to ∼2.4 with photon energy between 3 and 30 keV. PWN G54.1+0.3's X-ray spectrum is consistent with a broken power law, with break energy Ebreak ≈ 5 keV, consistent with synchrotron cooling of a single power-law particle spectrum. The best-fit broadband spectral energy distribution model after the inclusion of this new spectral data indicates a maximum particle energy  Emax∼  400 TeV. We discuss PSR J1930+1852 and PWN G54.1+0.3 in the context of other PWNe powered by young energetic pulsars.

Keywords: Supernova remnants, Pulsars, Pulsar wind nebulae
The Correspondence between Leaky-box and Diffusion Models of Cosmic-Ray Propagation. The leaky-box model and the attendant concept of path-length distribution of cosmic rays were invented in the mid-1960s. Even though versatile computational packages such as GALPROP and DRAGON with the diffusion approach are now available for analyzing cosmic-ray data, the concepts of the leaky box and path-length distribution continue to be adopted extensively. We show here mathematically that there is a close correspondence between the two approaches: the path lengths or resident times of the leaky-box models are similar to the "impulse response functions" of complex dynamical systems and are intuitively transparent. The results provided by the leaky-box model are valid when used judiciously.

Keywords: Galactic cosmic rays, Particle astrophysics, Cosmic rays
Revealing the χ<SUB>eff</SUB>–q Correlation among Coalescing Binary Black Holes and Tentative Evidence for AGN-driven Hierarchical Mergers. The origin of the correlation between the effective spins (χeff) and mass ratios (q) of LIGO–Virgo–KAGRA's binary black holes (BBHs) is still an open question. Motivated by the recent identification of two subpopulations of the BBHs, in this work we investigate the potential χeff–q correlation for each subpopulation. Surprisingly, the χeff–q correlation either significantly weakens or disappears for the low-mass subpopulation if we introduce a second χeff distribution for the high-mass subpopulation, which likely originates from hierarchical mergers. This suggests that the χeff–q correlation in the overall population can be explained by the superposition of two distinct subpopulations. We find Bayesian evidence strongly favoring two separate χeff distributions over a single mass ratio–dependent distribution, with Bayes factors  lnB&gt;4.2 . The first subpopulation has a narrow χeff distribution peaking at ∼0.05, whose primary mass function shows a rapid decline beyond ∼40M⊙, in agreement with first-generation BBHs. The second χeff distribution is broad and peaks at μχ,2 ∼ 0.4, aligning with predictions for hierarchical mergers in active galactic nucleus (AGN) disks. However, we cannot exclude negative χeff values in the second subpopulation, suggesting that hierarchical mergers might occur both in AGN disks and stellar clusters. Furthermore, the inferred second χeff distribution might alternatively arise from other formation channels, such as stable mass transfer or chemically homogeneous evolution, if not interpreted as hierarchical mergers.

Keywords: Compact binary stars, Stellar mass black holes, Black holes