Sazuna/UAT_keywords huggingface dataset:
Near-core Acoustic Glitches Are Not Oscillatory: Consequences for Asteroseismic Probes of Convective Boundary Mixing. Asteroseismology has been used extensively in recent years to study the interior structure and physical processes of main-sequence stars. We consider prospects for using pressure modes (p-modes) near the frequency of maximum oscillation power to probe the structure of the near-core layers of main-sequence stars with convective cores by constructing stellar model tracks. Within our mass range of interest, the inner turning point of p-modes as determined by the Jeffreys-Wentzel-Kramers-Brillouin (JWKB) approximation evolves in two distinct phases during the main sequence, implying a sudden loss of near-core sensitivity during the discontinuous transition between the two phases. However, we also employ non-JWKB asymptotic analysis to derive a contrasting set of expressions for the effects that these structural properties will have on the mode frequencies, which do not encode any such transition. We show analytically that a sufficiently near-core perturbation to the stellar structure results in nonoscillatory, degree-dependent perturbations to the star's oscillation mode frequencies, contrasting with the case of an outer glitch. We also demonstrate numerically that these near-core acoustic glitches exhibit strong angular degree dependence, even at low degree, agreeing with the non-JWKB analysis, rather than the degree-independent oscillations that emerge from JWKB analyses. These properties have important implications for using p-modes to study near-core mixing processes for intermediate-mass stars on the main sequence, as well as for the interpretation of near-center acoustic glitches in other astrophysical configurations, such as red giants.

Keywords: Main sequence, Stellar physics, Asteroseismology, Stellar evolution
Dwarf Galaxy Formation with and without Dark Matter-Baryon Streaming Velocities. We study how supersonic streaming velocities of baryons relative to dark matter-a large-scale effect imprinted at recombination and coherent over ~3 Mpc scales-affect the formation of dwarf galaxies at z ≳ 5. We perform cosmological hydrodynamic simulations, including and excluding streaming velocities, in regions centered on halos with M vir(z = 0) ≈ 1010 M ⊙; the simulations are part of the Feedback In Realistic Environments (FIRE) project and run with FIRE-3 physics. Our simulations comprise many thousands of systems with halo masses between M vir = 2 × 105 M ⊙ and 2 × 109 M ⊙ in the redshift range z = 20-5. A few hundred of these galaxies form stars and have stellar masses ranging from 100 to 107 M ⊙. While star formation is globally delayed by approximately 50 Myr in the streaming relative to nonstreaming simulations and the number of luminous galaxies is correspondingly suppressed at high redshift in the streaming runs, these effects decay with time. By z = 5, the properties of the simulated galaxies are nearly identical in the streaming versus nonstreaming runs, indicating that any effects of streaming velocities on the properties of galaxies at the mass scale of classical dwarfs and larger do not persist to z = 0.

Keywords: Early universe, Dwarf galaxies, Population III stars, Primordial galaxies
Prompt Detection of Fast Optical Bursts with the Vera C. Rubin Observatory. The transient optical sky has remained largely unexplored on very short timescales. While there have been some experiments searching for optical transients from minutes to years, none have had the capability to distinguish millisecond fast optical bursts (FOBs). Such very fast transients could be the optical counterparts of fast radio bursts, the prompt emission from γ-ray bursts, or other previously unknown phenomena. Here, we investigate a novel approach to the serendipitous detection of FOBs, which relies on searching for anomalous spatial images. In particular, due to their short duration, the seeing-distorted images of FOBs should look characteristically different than those of steady sources in a standard optical exposure of finite duration. We apply this idea to simulated observations with the Vera C. Rubin Observatory, produced by tracing individual photons through a turbulent atmosphere, and down through the optics and camera of the Rubin telescope. We compare these simulated images to steady-source star simulations in 15 s integrations, the nominal Rubin exposure time. We report the classification accuracy results of a neural network classifier for distinguishing FOBs from steady sources. From this classifier, we derive constraints in duration-intensity parameter space for unambiguously identifying FOBs in Rubin observations. We conclude with estimates of the total number of detections of FOB counterparts to FRBs expected during the 10 yr Rubin Legacy Survey of Space and Time.

Keywords: Optical bursts, High energy astrophysics, Transient sources, Burst astrophysics, Radio transient sources
Spherical Harmonics for the 1D Radiative Transfer Equation. I. Reflected Light. A significant challenge in radiative transfer theory for atmospheres of exoplanets and brown dwarfs is the derivation of computationally efficient methods that have adequate fidelity to more precise, numerically demanding solutions. In this work, we extend the capability of the first open-source radiative transfer model for computing the reflected light of exoplanets at any phase geometry, PICASO (Planetary Intensity Code for Atmospheric Spectroscopy Observations). Until now, PICASO has implemented two-stream approaches to the solving the radiative transfer equation for reflected light, in particular following the derivations of Toon et al. In order to improve the model accuracy, we have considered higher-order approximations of the phase functions; namely, we have increased the order of approximation from two to four, using spherical harmonics. The spherical harmonics approximation decouples spatial and directional dependencies by expanding the intensity and phase function into a series of spherical harmonics, or Legendre polynomials, allowing for analytical solutions for low-order approximations to optimize computational efficiency. We rigorously derive the spherical harmonics method for reflected light and benchmark the four-term method (SH4) against Toon et al. and two independent and higher-fidelity methods (CDISORT and doubling method). On average, the SH4 method provides an order-of-magnitude increase in accuracy, compared to Toon et al. Finally, we implement SH4 within PICASO and observe only a modest increase in computational time, compared to two-stream methods (20% increase).

Keywords: Planetary atmospheres, Radiative transfer equation, Radiative transfer, Radiative transfer simulations, Exoplanet atmospheres
Properties of Forbush Decreases with AMS-02 Daily Proton Flux Data. A Forbush decrease (FD) is a sudden reduction of Galactic Cosmic Rays (GCRs) that is usually caused by intense solar wind transients, such as Interplanetary Coronal Mass Ejections (ICMEs) and Corotating Interaction Regions (CIRs). Using daily proton fluxes measured by AMS-02 between 2011 May and 2019 October, we identified 142 FD events with an automatic systematic analysis method. The properties of 47 FDs caused by ICMEs and of 54 FDs caused by CIRs were analyzed. We found that the rigidity dependence of the GCR flux decrease is generally better described by an exponential function for both ICME and CIR FDs. We also found that the FD Amplitude of ICME FDs has a moderate correlation with the minimum Dst index and a number of solar wind parameters, such as maximum temperature, pressure, and magnetic field. For CIR FD events, neither FD Amplitude nor Maximum Affected Rigidity had a significant correlation with solar wind parameters.

Keywords: Forbush effect, Galactic cosmic rays, Solar coronal mass ejections, Solar activity, Corotating streams
3D Modeling of the Molecular Gas Kinematics in Optically Selected Jellyfish Galaxies. Cluster galaxies are subject to the ram pressure exerted by the intracluster medium, which can perturb or even strip away their gas while leaving the stars undisturbed. We model the distribution and kinematics of the stars and the molecular gas in four late-type cluster galaxies (JO201, JO204, JO206, and JW100), which show tails of atomic and ionized gas indicative of ongoing ram pressure stripping. We analyze MUSE@VLT data and CO data from the Atacama Large Millimeter Array searching for signatures of radial gas flows, ram pressure stripping, and other perturbations. We find that all galaxies, with the possible exception of JW100, host stellar bars. Signatures of ram pressure are found in JO201 and JO206, which also shows clear indications of ongoing stripping in the molecular disk outskirts. The stripping affects the whole molecular gas disk of JW100. The molecular gas kinematics in JO204 is instead dominated by rotation rather than ram pressure. We also find indications of enhanced turbulence of the molecular gas compared to field galaxies. Large-scale radial flows of molecular gas are present in JO204 and JW100, but more uncertain in JO201 and JO206. We show that our sample follows the molecular gas mass-size relation, confirming that it is essentially independent of environment even for the most extreme cases of stripping. Our findings are consistent with the molecular gas being affected by the ram pressure on different timescales and less severely than the atomic and ionized gas phases, likely because the molecular gas is denser and more gravitationally bound to the galaxy.

Keywords: Galaxy clusters, Molecular gas, Disk galaxies, Galaxy environments, Stellar kinematics, Ram pressure stripped tails, Active galaxies, Galaxy kinematics
ALMA View of the High-velocity-dispersion Compact Cloud CO 0.02-0.02 at the Galactic Center. We report the results of observations toward the center of the molecular cloud CO 0.02-0.02 made using the Atacama Large Millimeter/Submillimeter Array. The successfully obtained 1″ resolution images of CO J = 3-2, H13CN J = 4-3, H13CO+ J = 4-3, SiO J = 8-7, CH3OH J ${}_{{\text{}}{K}_{a},{K}_{c}}$ = 71,7-61,6 A+ lines, and 900 μm continuum show several new features, which have not been identified in previous observations. The dense gas probe (H13CN, SiO, CH3OH) images are dominated by a pair of northeast-southwest elongated filaments, which may be the main body of CO 0.02-0.02. Two striped patterns perpendicular to each other (F1 and F2) and a high-velocity feature (HV), which appear in different velocity ranges, were prominent in the CO image. An emission hole that may represent an expanding feature was found in the F1 velocity range. F2 appeared to align along the western edge of a 20 pc × 13 pc ellipse (the Large Shell) identified in the single-dish CO map. The HV contains eight compact clumps at the positive high-velocity end of the CO emissions. Based on these results, we propose a formation scenario for CO 0.02-0.02; internal explosions of supernovae, external perturbations by the Large Shell, and gravitational acceleration by a less-luminous star cluster have formed CO 0.02-0.02 in its current state.

Keywords: Submillimeter astronomy, Galactic center, Molecular clouds
Study of Spectral State Transitions in Black Hole Binaries. The aim of our work is to study the origin of the spectral transitions of transient black hole binaries. In this work, we find signatures of spectral state transition (hard to soft state) while studying the radiative shock for the accretion flow. The gradient of the energy dissipation curve shows a sudden break for certain critical flow parameters when the post-shock dissipation is maximum. This particular feature is common to all spins, and the transitions are well observed. We have identified all the critical flow parameters for different black hole spins. With the dissipation, the inner edge of the disk or the geometry of the post-shock corona reduces progressively and attains a minimum for maximum dissipation. The spin enhances the maximum dissipation further. Using the exact general relativistic framework, we therefore systematically study the various dynamical properties of radiative/dissipative shocks in accretion flows to understand the observed phenomena, namely, the variation of the hard intensity emitted from the evolving Comptonizing medium, the spectral transitions, and their entanglement with the inner edge of the disk, etc. The results presented here might be useful in finding the variation of the hardness ratio and could be a first step to procuring the "q" diagram theoretically.

Keywords: Accretion, General relativity, Shocks, Relativistic fluid dynamics, Astrophysical black holes
Magnetic Braking with MESA Evolutionary Models in the Single Star and Low-mass X-Ray Binary Regimes. Magnetic braking has a prominent role in driving the evolution of close low-mass binary systems and heavily influences the rotation rates of low-mass F- and later-type stars with convective envelopes. Several possible prescriptions that describe magnetic braking in the context of 1D stellar evolution models currently exist. We test four magnetic braking prescriptions against both low-mass X-ray binary orbital periods from the Milky Way and single-star rotation periods observed in open clusters. We find that the data favor a magnetic braking prescription that follows a rapid transition from fast to slow rotation rates, exhibits saturated (inefficient) magnetic braking below a critical Rossby number, and that is sufficiently strong to reproduce ultra-compact X-ray binary systems. Of the four prescriptions tested, these conditions are satisfied by a braking prescription that incorporates the effect of high-order magnetic field topology on angular momentum loss. None of the braking prescriptions tested are able to replicate the stalled spin down observed in open cluster stars aged 700-1000 Myr or so, with masses ≲0.8 M ⊙.

Keywords: Stellar evolutionary models, Stellar magnetic fields, Low mass stars, Low-mass x-ray binary stars, Stellar evolution
Multicollision Internal Shock Lepto-hadronic Models for Energetic Gamma-Ray Bursts (GRBs). For a subpopulation of energetic gamma-ray bursts (GRBs), a moderate baryonic loading may suffice to power ultra-high-energy cosmic rays (UHECRs). Motivated by this, we study the radiative signatures of cosmic-ray protons in the prompt phase of energetic GRBs. Our framework is the internal shock model with multicollision descriptions of the relativistic ejecta (with different emission regions along the jet), plus time-dependent calculations of photon and neutrino spectra. Our GRB prototypes are motivated by Fermi-Large Area Telescope-detected GRBs (including GRB 221009A) for which further, owing to the large energy flux, neutrino nonobservation of single events may pose a strong limit on the baryonic loading. We study the feedback of protons on electromagnetic spectra in synchrotron- and inverse Compton-dominated scenarios to identify the multiwavelength signatures, to constrain the maximally allowed baryonic loading, and to point out the differences between hadronic and inverse Compton signatures. We find that hadronic signatures appear as correlated flux increases in the optical-UV to soft X-ray and GeV-TeV gamma-ray ranges in the synchrotron scenarios, whereas they are difficult to identify in inverse Compton-dominated scenarios. We demonstrate that baryonic loadings around 10, which satisfy the UHECR energetic requirements, do not distort the predicted photon spectra in the Fermi Gamma-Ray Burst Monitor range and are consistent with constraints from neutrino data if the collision radii are large enough (i.e., the time variability is not too short). It therefore seems plausible that under the condition of large dissipation radii a population of energetic GRBs can be the origin of the UHECRs.

Keywords: Gamma-ray bursts, High energy astrophysics, Non-thermal radiation sources, Cosmological neutrinos, Cosmic rays
Cosmic Supernova Neutrino and Gamma-Ray Backgrounds in the MeV Regime. Cosmic multimessenger backgrounds include relic diffuse components created in the early universe and contributions from individual sources. Here, we study both type Ia supernovae (SNe Ia) and core-collapse supernovae (CCSNe) contributions to the diffuse neutrino and gamma-ray backgrounds in the MeV regime referred to as DSNB and DSGB respectively. We show that the diffuse SN Ia background is 106 times lower (for ${\overline{\nu }}_{e}$ ) than the CCSN background making it negligible. Our predicted DSNB ${\overline{\nu }}_{e}$ flux at earth in the 19.3-32 MeV regime is 0.36 ν cm-2 s-1. We also find that the DSNB flux in the energy range from 11.3 to 32 MeV varies by +29% with a change in the SFRD model from Madau &amp; Fragos which yielded a minimum predicted flux, to the extragalactic background light reconstruction model (maximum predicted flux). The diffuse SN Ia gamma-ray background and its dependence on the progenitor supernova delay time distribution are also evaluated. Furthermore, we address the origin of the CGB (Cosmic Gamma-ray Background) in the 0.1-7 MeV regime by adding contributions from sources such as SNe Ia, CCSNe, radio-quiet Active Galactic Nuclei, Flat spectrum radio quasars (FSRQs) and Neutron star-neutron star mergers. We find that our modeled background (including uncertainties) matches the observed CGB above 1.0 MeV, but is a factor ≈2 lower than the observed flux in the 0.1-1.0 MeV range, highlighting the need for future MeV missions to establish the CGB spectrum more reliably, and to possibly identify additional sources or even source classes in the underexplored MeV band.

Keywords: Cosmology, Cosmological evolution, High energy astrophysics, Core-collapse supernovae, Neutrino astronomy, Type Ia supernovae, Star formation, Gamma-ray astronomy, Supernovae
The Intrinsic Statistical Properties and Correlations of Short Gamma-Ray Bursts. The intrinsic statistical properties and correlations of short gamma-ray bursts (SGRBs) have not been fully determined, due to the limitations of observations. In this paper, we compile a more extensive sample of 82 SGRBs with measured redshifts and present a comprehensive study of their intrinsic characteristics. We obtain the median values of the intrinsic duration (T 90,z), peak energy (E p,z), isotropic energy (E iso), and peak luminosity (L iso) as 0.47 s, 466 keV, 8.21 ×1050 erg, and 3.22 × 1051 erg s-1, respectively. We update the spectrum-energy correlations, and report ${E}_{{\rm{p}},{\rm{z}}}\propto {E}_{\mathrm{iso}}^{0.36\pm 0.05}$ and ${E}_{{\rm{p}},{\rm{z}}}\propto {L}_{\mathrm{iso}}^{0.33\pm 0.04}$ , which further confirm the previous results that the E p,z-E iso correlations of SGRBs and long gamma-ray bursts (LGRBs) are different and that this correlation can be used to distinguish GRB types. We report for the first time that there is a tighter correlation between the isotropic energy of the prompt emission of SGRBs and the star formation rate of their host galaxies, which reads $\mathrm{sSFR}\propto {E}_{\mathrm{iso}}^{0.38\pm 0.11}$ . Using the measured jet break time (t jet) of 11 SGRBs, we tentatively investigate the E iso-E p,z-t jet,z and L iso-E p,z-t jet,z correlations of SGRBs and find that three-parameter correlations of SGRBs also exist and are different from those of LGRBs. Based on the E iso-E p,z-t jet,z correlation, we estimate the t jet,z values of other SGRBs and calculate the opening angles of SGRBs. We find that the median value of the SGRB opening angle is 7.°5, which is larger than that of LGRBs.

Keywords: Gamma-ray bursts
Jet Formation in 3D GRMHD Simulations of Bondi-Hoyle-Lyttleton Accretion. A black hole (BH) traveling through a uniform, gaseous medium is described by Bondi-Hoyle-Lyttleton (BHL) accretion. If the medium is magnetized, then the black hole can produce relativistic outflows. We performed the first 3D, general-relativistic magnetohydrodynamic simulations of BHL accretion onto rapidly rotating black holes using the H-AMR code, where we mainly varied the strength of a background magnetic field that threads the medium. We found that the ensuing accretion continuously drags the magnetic flux to the BH, which accumulates near the event horizon until it becomes dynamically important. Depending on the strength of the background magnetic field, the BHs can sometimes launch relativistic jets with high enough power to drill out of the inner accretion flow, become bent by the headwind, and escape to large distances. For stronger background magnetic fields, the jets are continuously powered, while at weaker field strengths they are intermittent, turning on and off depending on the fluctuating gas and magnetic flux distributions near the event horizon. We find that our jets reach extremely high efficiencies of ~100%-300%, even in the absence of an accretion disk. We also calculated the drag forces exerted by the gas onto to the BH and found that the presence of magnetic fields causes the drag forces to be much less efficient than in unmagnetized BHL accretion. They can even sometimes become negative, accelerating the BH rather than slowing it down. Our results extend classical BHL accretion to rotating BHs moving through magnetized media, and demonstrate that accretion and drag are significantly altered in this environment.

Keywords: High energy astrophysics, Relativistic jets, Bondi accretion, Stellar winds, Astrophysical black holes
Exoplanet Nodal Precession Induced by Rapidly Rotating Stars: Impacts on Transit Probabilities and Biases. For the majority of short-period exoplanets transiting massive stars with radiative envelopes, the spin angular momentum of the host star is greater than the planetary orbital angular momentum. In this case, the orbits of the planets will undergo nodal precession, which can significantly impact the probability that the planets transit their parent star. In particular, for some combinations of the spin-orbit angle ψ and the inclination of the stellar spin i *, all such planets will eventually transit at some point over the duration of their precession period. Thus, as the time over which the sky has been monitored for transiting planets increases, the frequency of planets with detectable transits will increase, potentially leading to biased estimates of exoplanet occurrence rates, especially orbiting more-massive stars. Furthermore, due to the dependence of the precession period on orbital parameters such as spin-orbit misalignment, the observed distributions of such parameters may also be biased. We derive the transit probability of a given exoplanet in the presence of nodal precession induced by a rapidly spinning host star. We find that the effect of nodal precession has already started to become relevant for some short-period planets, i.e., hot Jupiters, orbiting massive stars, by increasing transit probabilities by order of a few percent for such systems within the original Kepler field. We additionally derive simple expressions to describe the time evolution of the impact parameter b for applicable systems, which should aid in future investigations of exoplanet nodal precession and spin-orbit alignment.

Keywords: Hot Jupiters, Transits, Exoplanets