adsabs/SciX_UAT_keywords huggingface dataset:
Three-dimensional Core-collapse Supernova Simulations with 160 Isotopic Species Evolved to Shock Breakout

We present three-dimensional simulations of core-collapse supernovae using the FLASH code that follow the progression of the explosion to the stellar surface, starting from neutrino radiation hydrodynamic simulations of the neutrino-driven phase performed with the CHIMERA code. We consider a 9.6 M⊙ zero-metallicity progenitor starting from both 2D and 3D CHIMERA models and a 10 M⊙ solar-metallicity progenitor starting from a 2D CHIMERA model, all simulated until shock breakout in 3D while tracking 160 nuclear species. The relative velocity difference between the supernova shock and the metal-rich Rayleigh-Taylor (R-T) "bullets" determines how the metal-rich ejecta evolves as it propagates through the density profile of the progenitor and dictates the final morphology of the explosion. We find maximum 56Ni velocities of ~1950 and ~1750 km s-1 at shock breakout from 2D and 3D 9.6 M⊙ CHIMERA models, respectively, due to the bullets' ability to penetrate the He/H shell. When mapping from 2D, we find that the development of higher-velocity structures is suppressed when the 2D CHIMERA model and 3D FLASH model meshes are aligned. The development of faster-growing spherical-bubble structures, as opposed to the slower-growing toroidal structure imposed by axisymmetry, allows for interaction of the bullets with the shock and seeds further R-T instabilities at the He/H interface. We see similar effects in the 10 M⊙ model, which achieves maximum 56Ni velocities of ~2500 km s-1 at shock breakout.

Keywords: hydrodynamics; massive stars; core-collapse supernovae; supernovae; stellar evolution
Controlling Randomization in Astronomy Simulations

As the primary requirement, correctly implementing and controlling random number generation is vital for a range of scientific analyses and simulations across astronomy and planetary science. Beyond advice on how to set the seed, there is little guidance in the literature for how best to handle pseudo-random number generation in the current era of open-source astronomical software development. We present our methodology for implementing a pseudo-random number generation in astronomy simulations and software and share the short lines of python code that create the generator. Without sacrificing randomization at run time, our strategy ensures reproducibility on a per function/module basis for unit testing and for run time debugging where there may be multiple functions requiring lists of randomly generated values that occur before a specific function is executed.

Keywords: open source software
Population Properties of Gravitational-wave Neutron Star-Black Hole Mergers

Over the course of the third observing run of the LIGO-Virgo-KAGRA Collaboration, several gravitational-wave (GW) neutron star-black hole (NSBH) candidates have been announced. By assuming that these candidates are real signals with astrophysical origins, we analyze the population properties of the mass and spin distributions for GW NSBH mergers. We find that the primary BH mass distribution of NSBH systems, whose shape is consistent with that inferred from the GW binary BH (BBH) primaries, can be well described as a power law with an index of $\alpha ={4.8}_{-2.8}^{+4.5}$ plus a high-mass Gaussian component peaking at $\sim {33}_{-9}^{+14}\,{M}_{\odot }$ . The NS mass spectrum could be shaped as a nearly flat distribution between ~1.0 and 2.1 M ⊙. The constrained NS maximum mass agrees with that inferred from NSs in our Galaxy. If GW190814 and GW200210 are NSBH mergers, the posterior results of the NS maximum mass would be always larger than ~2.5 M ⊙ and significantly deviate from that inferred in Galactic NSs. The effective inspiral spin and effective precession spin of GW NSBH mergers are measured to potentially have near-zero distributions. The negligible spins for GW NSBH mergers imply that most events in the universe should be plunging events, which support the standard isolated formation channel of NSBH binaries. More NSBH mergers to be discovered in the fourth observing run would help to more precisely model the population properties of cosmological NSBH mergers.

Keywords: gravitational waves; neutron stars; black holes
Antaeus: A Retrograde Group of Tidal Debris in the Milky Way's Disk Plane

We present the discovery of a wide retrograde moving group in the disk plane of the Milky Way using action-angle coordinates derived from the Gaia DR3 catalog. The structure is identified from a sample of its members that are currently almost at the pericenter of their orbit and are passing through the solar neighborhood. The motions of the stars in this group are highly correlated, indicating that the system is probably not phase mixed. With a width of at least 1.5 kpc and with a probable intrinsic spread in metallicity, this structure is most likely the wide remnant of a tidal stream of a disrupted ancient dwarf galaxy (age ~12 Gyr, <[Fe/H]> ~ -1.74). The structure presents many similarities (e.g., in energy, angular momentum, metallicity, and eccentricity) with the Sequoia merging event. However, it possesses extremely low vertical action J z , which makes it unique even among Sequoia dynamical groups. As the low J z may be attributable to dynamical friction, we speculate that these stars may be the remnants of the dense core of the Sequoia progenitor.

Keywords: galaxies; stellar streams; milky way dynamics; local group; milky way stellar halo; tidal disruption; milky way disk
Super-Earth LHS3844b is Tidally Locked

Short-period exoplanets on circular orbits are thought to be tidally locked into synchronous rotation. If tidally locked, these planets must possess permanent day- and night-sides, with extreme irradiation on the dayside and none on the nightside. However, so far the tidal locking hypothesis for exoplanets is supported by little to no empirical evidence. Previous work showed that the super-Earth LHS 3844b likely has no atmosphere, which makes it ideal for constraining the planet's rotation. Here we revisit the Spitzer phase curve of LHS 3844b with a thermal model of an atmosphere-less planet and analyze the impact of nonsynchronous rotation, eccentricity, tidal dissipation, and surface composition. Based on the lack of observed strong tidal heating we rule out rapid nonsynchronous rotation (including a Mercury-like 3:2 spin–orbit resonance) and constrain the planet's eccentricity to less than ∼0.001 (more circular than Io's orbit). In addition, LHS 3844b's phase curve implies that the planet either still experiences weak tidal heating via a small-but-nonzero eccentricity (requiring an undetected orbital companion), or that its surface has been darkened by space weathering; of these two scenarios we consider space weathering more likely. Our results thus support the hypothesis that short-period rocky exoplanets are tidally locked, and further show that space weathering can significantly modify the surfaces of atmosphere-less exoplanets.

Keywords: exoplanets; extrasolar rocky planets; exoplanet surfaces; tidal interaction; solid body tides; light curves; space weather; exoplanet surface characteristics; regolith
Advective Accretion onto a Nonspherical Accretor in White Dwarf and Neutron Star Binaries: A New Scenario of Shock Formation

Numerous studies on hydrodynamics of the Keplerian as well as the sub-Keplerian accretion disk around a compact object (e.g., white dwarf (WD), neutron star (NS), or a black hole) have attempted to explain the observed UV, soft, and hard X-ray spectra. Although, when the compact object (e.g., a WD or an NS) has a finite surface, its rapid rotation, the stellar magnetic field could cause deformation of the spherical symmetry. Earlier studies on the Keplerian disk showed that a deviation from the spherical symmetry of the compact object could affect the observed light curve and spectra at high frequencies. Here, we have explored the effect of the nonspherical nature of a compact object on the hydrodynamics of an optically thin, geometrically thick sub-Keplerian advective flow. We find that due to the nonspherical shape of the central accretor, there is a possibility to trigger Rankine-Hugoniot shock in the sub-Keplerian advective flow close to the accretor without considering any general relativistic effect or presence of the hard surface of the star. Our results are more relevant for accretion onto a WD as hardly any general relativistic effect will come into the picture. We propose that some observational features, e.g., high significance of fitting the spectra with multi-temperature plasma models rather than single-temperature models, and variable efficiency of X-ray emission (X-ray luminosity in comparison with the optical and UV luminosity of the disk) in nonmagnetic cataclysmic variables can be explained by the presence of a shock in the sub-Keplerian advective flow.

Keywords: high energy astrophysics; cataclysmic variable stars; white dwarf stars; accretion; shocks
Swift/UVOT+MaNGA (SwiM) Value-added Catalog

We introduce the Swift/UVOT+MaNGA (SwiM) value-added catalog, which comprises 150 galaxies that have both Sloan Digital Sky Survey (SDSS)/MaNGA integral field spectroscopy and archival Swift/UVOT near-UV (NUV) images. The similar angular resolution between the three Swift/UVOT NUV images and the MaNGA maps allows for a high-resolution comparison of optical and NUV indicators of star formation, crucial for constraining quenching and attenuation in the local universe. The UVOT NUV images, SDSS images, and MaNGA emission line and spectral index maps have all been spatially matched and reprojected to match the point-spread function (PSF) and pixel sampling of the Swift/UVOT uvw2 images and are presented in the same coordinate system for each galaxy. The spectral index maps use the definition first adopted by Burstein et al., which makes it more convenient for users to compute spectral indices when binning the maps. Spatial covariance is properly taken into account in propagating the uncertainties. We also provide a catalog that includes PSF-matched aperture photometry in the SDSS optical and Swift NUV bands. In an earlier companion paper, we used a subset of these galaxies to explore the attenuation laws of kiloparsec-sized star-forming regions. The catalog, maps for each galaxy, and associated data models are publicly available on the SDSS website.

Keywords: catalogs; galaxies; astronomy data analysis; sloan photometry; ultraviolet photometry; spectroscopy; star formation
The Circular Velocity Curve of the Milky Way from 5-25 kpc Using Luminous Red Giant Branch Stars

We present a sample of 254,882 luminous red giant branch (LRGB) stars selected from the APOGEE and LAMOST surveys. By combining photometric and astrometric information from the Two Micron All Sky Survey and Gaia survey, the precise distances of the sample stars are determined by a supervised machine-learning algorithm: the gradient-boosted decision trees. To test the accuracy of the derived distances, member stars of globular clusters (GCs) and open clusters are used. The tests by cluster member stars show a precision of about 10% with negligible zero-point offsets, for the derived distances of our sample stars. The final sample covers a large volume of the Galactic disk(s) and halo of 0 < R < 30 kpc and ∣Z∣ ≤ 15 kpc. The rotation curve (RC) of the Milky Way across the radius of 5 ≲ R ≲ 25 kpc has been accurately measured with ~54,000 stars of the thin disk population selected from the LRGB sample. The derived RC shows a weak decline along R with a gradient of -1.83 ± 0.02 (stat.) ± 0.07 (sys.) km s-1 kpc-1, in excellent agreement with the results measured by previous studies. The circular velocity at the solar position, yielded by our RC is 234.04 ± 0.08 (stat.) ± 1.36 (sys.) km s-1, again in great consistency with other independent determinations. From the newly constructed RC, as well as constraints from other data, we have constructed a mass model for our Galaxy, yielding a mass of the dark matter halo of M 200 = (8.05 ± 1.15) × 1011 M ⊙ with a corresponding radius of R 200 = 192.37 ± 9.24 kpc and a local dark matter density of 0.39 ± 0.03 GeV cm-3.

Keywords: galaxy rotation curves; distance measure; milky way dynamics; galaxy kinematics
VLBI Data Processing on Coronal Radio-sounding Experiments of Mars Express

The ESA's Mars Express solar corona experiments were performed at two solar conjunctions in the years 2015 and 2017 by a number of radio telescopes in the European VLBI Network. This paper presents the methods to measure the frequency and phase fluctuations of the spacecraft radio signal, and the applications to study the characteristics of the plasma turbulence effects on the signal at a single station and at multiple stations via cross correlation. The power spectra of the frequency fluctuations observed between 4.9 and 76.3 Rs have a power-law shape close to a Kolmogorov spectrum over the frequency interval νlo < ν < νup, where the nominal value of νlo is set to 3 mHz and νup is in the range of 0.03-0.15 Hz. The rms of the frequency fluctuations is presented as a function of the heliocentric distance. Furthermore, we analyze the variations of the electron column density fluctuations at solar offsets 4.9 Rs and 9.9 Rs and the cross-correlation products between the VLBI stations. The power density of the differential fluctuations between different stations decreases at ν < 0.01 Hz. Finally, the fast flow speeds of solar wind >700 km s-1 are derived from the cross correlation of frequency fluctuations at ν < 0.01 Hz. The fast flow speeds of solar wind correspond to the high heliolatitude of the coronal region that the radio rays passed. The VLBI observations and analysis methods can be used to study the electron column density fluctuations and the turbulence at multiple spatial points in the inner solar wind by providing multiple lines of sight between the Earth and the spacecraft.

Keywords: solar wind; very long baseline interferometry; deep space probes
A Robust RFI Identification Method for Radio Interferometry Based on LightGBM

Radio frequency interference is an essential factor affecting the observation data quality of radio telescopes. In constructing the Square Kilometer Array (SKA) radio interferometer, dealing with radio frequency interference (RFI) effectively is always a hot issue in data processing. Traditional identification methods have poor precision or recall, and existing machine-learning-based methods have complicated models and low processing efficiency. We propose a LightGBM identification method based on previous machine-learning research to identify RFI. Based on the data of SKA1-LOW simulation observations, we construct five visibility function data sets, one for modeling and the rest for validation. The experimental results show that the F 2-score reaches 0.9583, and the training and prediction speed are much more efficient than those of convolutional neural networks in a similar recent study. Then, we further investigate the effectiveness of this model in identifying RFI from actual MeerKAT observations. The results show that the overall effectiveness is comparable to tools such as Tfcrop and Rflag, improving over existing methods in identification speed.

Keywords: astronomical simulations; astronomy data analysis; astronomy data modeling; classification; neural networks; astrostatistics techniques
A Hubble Space Telescope Search for r-Process Nucleosynthesis in Gamma-Ray Burst Supernovae

The existence of a secondary (in addition to compact object mergers) source of heavy element (r-process) nucleosynthesis, the core-collapse of rapidly rotating and highly magnetized massive stars, has been suggested by both simulations and indirect observational evidence. Here, we probe a predicted signature of r-process enrichment, a late-time (≳40 days post-burst) distinct red color, in observations of gamma-ray burst supernovae (GRB-SNe), which are linked to these massive star progenitors. We present optical to near-IR color measurements of four GRB-SNe at z ≲ 0.4, extending out to >500 days post-burst, obtained with the Hubble Space Telescope and large-aperture ground-based telescopes. Comparison of our observations to models indicates that GRBs 030329, 100316D, and 130427A are consistent with both no enrichment and producing 0.01–0.15 M ⊙ of r-process material if there is a low amount of mixing between the inner r-process ejecta and outer supernova (SN) layers. GRB 190829A is not consistent with any models with r-process enrichment ≥0.01 M ⊙. Taken together the sample of GRB-SNe indicates color diversity at late times. Our derived yields from GRB-SNe may be underestimated due to r-process material hidden in the SN ejecta (potentially due to low mixing fractions) or the limits of current models in measuring r-process mass. We conclude with recommendations for future search strategies to observe and probe the full distribution of r-process produced by GRB-SNe.

Keywords: gamma-ray bursts; supernovae; r-process
Search for High-redshift Blazars with Fermi/LAT

High-z blazars (z ≥ 2.5) are the most powerful class of persistent γ-ray sources in the universe. These objects possess the highest jet powers and luminosities and have black hole masses often in excess of 109 solar masses. In addition, high-z blazars are important cosmological probes and serve as test objects for blazar evolution models. Due to their large distance, their high-energy emission typically peaks below the GeV range, which makes them difficult to study with Fermi/Large Area Telescope (LAT). Therefore, only the very brightest objects are detectable and, to date, only a small number of high-z blazars have been detected with Fermi/LAT. In this work, we studied the monthly binned long-term γ-ray emission of a sample of 176 radio and optically detected blazars that have not been reported as known γ-ray sources in the 3FGL catalog. To account for false-positive detections, we calculated monthly Fermi/LAT light curves for a large sample of blank sky positions and derived the number of random fluctuations that we expect at various test statistic (TS) levels. For a given blazar, a detection of TS > 9 in at least one month is expected ∼15% of the time. Although this rate is too high to secure detection of an individual source, half of our sample shows such single-month γ-ray activity, indicating a population of high-energy blazars at distances of up to z = 5.2. Multiple TS > 9 monthly detections are unlikely to happen by chance, and we have detected several individual new sources in this way, including the most distant γ-ray blazar, BZQ J1430+4204 (z = 4.72). Finally, two new γ-ray blazars at redshifts of z = 3.63 and z = 3.11 are unambiguously detected via very significant (TS > 25) flares in individual monthly time bins.

Keywords: blazars; gamma-ray astronomy; high-redshift galaxies
Subphotospheric Emission from Short Gamma-Ray Bursts: Protons Mold the Multimessenger Signals

The origin of the observed Band-like photon spectrum in short gamma-ray bursts (sGRBs) is a long-standing mystery. We carry out the first general relativistic magnetohydrodynamic simulation of an sGRB jet with initial magnetization σ 0 = 150 in dynamical ejecta from a binary merger. From this simulation, we identify regions along the jet of efficient energy dissipation due to magnetic reconnection and collisionless subshocks. Taking into account electron and proton acceleration processes, we solve for the first time the coupled transport equations for photons, electrons, protons, neutrinos, and intermediate particle species up to close to the photosphere (i.e., up to 1 × 1012 cm), accounting for all relevant radiative and cooling processes. We find that the subphotospheric multimessenger signals carry strong signatures of the hadronic interactions and their resulting particle cascades. Importantly, the spectral energy distribution of photons is significantly distorted with respect to the Wien one, commonly assumed below the photosphere. Our findings suggest that the bulk of the nonthermal photon spectrum observed in sGRBs can stem from hadronic processes occurring below the photosphere and previously neglected, with an accompanying energy flux of neutrinos peaking in the GeV energy range.

Keywords: particle astrophysics; gamma-ray bursts; transient sources
Observational Evidence for Large-scale Gas Heating in a Galaxy Protocluster at z = 2.30

We report a z = 2.30 galaxy protocluster (COSTCO-I) in the COSMOS field, where the Lyα forest as seen in the CLAMATO IGM tomography survey does not show significant absorption. This departs from the transmission-density relationship (often dubbed the fluctuating Gunn-Peterson approximation; FGPA) usually expected to hold at this epoch, which would lead one to predict strong Lyα absorption at the overdensity. For comparison, we generate mock Lyα forest maps by applying the FGPA to constrained simulations of the COSMOS density field and create mocks that incorporate the effects of finite sight-line sampling, pixel noise, and Wiener filtering. Averaged over r = 15 h -1 Mpc around the protocluster, the observed Lyα forest is consistently more transparent in the real data than in the mocks, indicating a rejection of the null hypothesis that the gas in COSTCO-I follows the FGPA (p = 0.0026, or 2.79σ significance). It suggests that the large-scale gas associated with COSTCO-I is being heated above the expectations of the FGPA, which might be due to either large-scale AGN jet feedback or early gravitational shock heating. COSTCO-I is the first known large-scale region of the IGM that is observed to be transitioning from the optically thin photoionized regime at cosmic noon to eventually coalesce into an intracluster medium (ICM) by z = 0. Future observations of similar structures will shed light on the growth of the ICM and allow constraints on AGN feedback mechanisms.

Keywords: intergalactic medium; quasar absorption line spectroscopy; high-redshift galaxy clusters; n-body simulations; intracluster medium
Direct Determination of the Activation Energy for Diffusion of OH Radicals on Water Ice

Using a combination of photostimulated desorption and resonance-enhanced multiphoton ionization methods, the behaviors of OH radicals on the surface of an interstellar ice analog were monitored at temperatures between 54 and 80 K. The OH number density on the surface of ultraviolet-irradiated compact amorphous solid water gradually decreased at temperatures above 60 K. Analyzing the temperature dependence of OH intensities with the Arrhenius equation, the decrease can be explained by the recombination of two OH radicals, which is rate-limited by thermal diffusion of OH. The activation energy for surface diffusion was experimentally determined for the first time to be 0.14 ± 0.01 eV, which is larger than or equivalent to those assumed in theoretical models. This value implies that the diffusive reaction of OH radicals starts to be activated at approximately 36 K on interstellar ice.

Keywords: astrochemistry; interstellar dust processes