Sazuna/UAT_keywords huggingface dataset:
The Effects of Nonequilibrium Velocity Distributions on Alfvén Ion-cyclotron Waves in the Solar Wind. In this work, we investigate how the complex structure found in solar wind proton velocity distribution functions (VDFs), rather than the commonly assumed two-component bi-Maxwellian structure, affects the onset and evolution of parallel-propagating microinstabilities. We use the Arbitrary Linear Plasma Solver, a numerical dispersion solver, to find the real frequencies and growth/damping rates of the Alfvén modes calculated for proton VDFs extracted from Wind spacecraft observations of the solar wind. We compare this wave behavior to that obtained by applying the same procedure to core-and-beam bi-Maxwellian fits of the Wind proton VDFs. We find several significant differences in the plasma waves obtained for the extracted data and bi-Maxwellian fits, including a strong dependence of the growth/damping rate on the shape of the VDF. By applying the quasilinear diffusion operator to these VDFs, we pinpoint resonantly interacting regions in velocity space where differences in VDF structure significantly affect the wave growth and damping rates. This demonstration of the sensitive dependence of Alfvén mode behavior on VDF structure may explain why the Alfvén ion-cyclotron instability thresholds predicted by linear theory for bi-Maxwellian models of solar wind proton background VDFs do not entirely constrain spacecraft observations of solar wind proton VDFs, such as those made by the Wind spacecraft.

Keywords: Space plasmas, Plasma physics, Solar wind, Plasma astrophysics, Alfven waves
Quasiperiodic Oscillation in Short Gamma-Ray Bursts from Black Hole-Neutron Star Mergers. Short-duration gamma-ray bursts (sGRBs) are commonly attributed to the mergers of double neutron stars (NSs) or the mergers of a neutron star with a black hole (BH). While the former scenario was confirmed by the event GW170817, the latter remains elusive. Here, we consider the latter scenario in which an NS is tidally disrupted by a fast-spinning low-mass BH and the accretion onto the BH launches a relativistic jet and hence produces an sGRB. The merging binary's orbit is likely misaligned with the BH's spin. Hence, the Lense-Thirring precession around the BH may cause a hyperaccreting thick disk to precess in a solid-body manner. We propose that a jet, initially aligned with the BH spin, is deflected and collimated by the wind from the disk, therefore being forced to precess along with the disk. This would result in a quasiperiodic oscillation or modulation in the gamma-ray light curve of the sGRB, with a quasi-period of ~0.01-0.1 s. The appearance of the modulation may be delayed respective to the triggering of the light curve. This feature, unique to the BH-NS merger, may have already revealed itself in a few observed sGRBs (such as GRB 130310A), and it carries the spin-orbit orientation information of the merging system. Identification of this feature would be a new approach to reveal spin-orbit misaligned merging BH-NS systems, which are likely missed by the current gravitational-wave searching strategy that is principally targeting aligned systems.

Keywords: Neutron stars, Gamma-ray bursts, Relativistic jets, Stellar mass black holes, Gravitational wave sources
Direct Collapse to Precursors of Supermassive Black Hole Seeds: Radiation-feedback-generated Outflows. We use high-resolution zoom-in cosmological simulations to model outflow triggered by radiation and thermal drivers around the central mass accumulation during direct collapse within the dark matter (DM) halo. The maximal resolution is 1.3 × 10-5 pc, and no restrictions are put on the geometry of the inflow/outflow. The central mass is considered prior to the formation of the supermassive black hole seed at a redshift of z ~ 15.9 and can constitute either a supermassive star (SMS) of ~105 M ⊙ surrounded by a growing accretion disk or a self-gravitating disk. The radiation transfer is modeled using the ray-tracing algorithm. Due to the high accretion rate of ~1 M ⊙ yr-1 determined by the DM halo, accretion is mildly supercritical, resulting in mildly supercritical luminosity that has only a limited effect on the accretion rate, with a duty cycle of ~0.9. We observe a fast development of hot cavities, which quickly extend into polar funnels and expand dense shells. Within the funnels, fast winds, ~103 km s-1, are mass-loaded by the accreting gas. We follow the expanding shells to ~1 pc, when the shell velocity remains substantially (~5 times) above the escape speed. The ionization cones formed by the central UV/X-ray completely ionize the cavities. Extrapolating the outflow properties shows that the halo material outside the shell will have difficulty stopping it. We therefore conclude that the expanding wind-driven shell will break out of the central parsec and will reach the halo virial radius. Finally, the anisotropic accretion flow on subparsec scales will attenuate the UV/soft X-rays on the H2. Hence, the formation of funnels and powerful outflows around, e.g., SMSs can have interesting observational corollaries.

Keywords: Supermassive black holes, Early universe, High energy astrophysics, Quasars, Plasma astrophysics, Active galactic nuclei, Radiative transfer, Galaxies
Constraints on Strong Phase Transitions in Neutron Stars. We study current bounds on strong first-order phase transitions (PTs) along the equation of state (EOS) of dense strongly interacting matter in neutron stars, under the simplifying assumption that on either side of the PT, the EOS can be approximated by a simple polytropic form. We construct a large ensemble of possible EOSs of this form, anchor them to chiral effective field theory calculations at nuclear density and perturbative Quantum Chromodynamics at high densities, and subject them to astrophysical constraints from high-mass pulsars and gravitational-wave observations. Within this setup, we find that a PT permits neutron-star solutions with larger radii, but only if the transition begins below twice nuclear saturation density. We also identify a large parameter space of allowed PTs currently unexplored by numerical-relativity studies. Additionally, we locate a small region of parameter space allowing twin-star solutions, though we find them to only marginally pass the current astrophysical constraints. Finally, we find that sizeable cores of high-density matter beyond the PT may be located in the centers of some stable neutron stars, primarily those with larger masses.

Keywords: Neutron stars, Neutron star cores, Nuclear astrophysics, Compact objects, Nuclear physics
Investigating Cosmological Models and the Hubble Tension Using Localized Fast Radio Bursts. We use the dispersion measure (DM) and redshift measurements of 24 localized fast radio bursts (FRBs) to compare cosmological models and investigate the Hubble tension. Setting a flat prior on the DM contribution from the Milky Way's halo, ${\mathrm{DM}}_{\mathrm{halo}}^{\mathrm{MW}}\in [5,\,80]\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$ , the best fit for flat ΛCDM is obtained with a Hubble constant ${H}_{0}={95.8}_{-9.2}^{+7.8}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ and a median matter density Ωm ≈ 0.66. The best fit for the R h = ct universe is realized with ${H}_{0}={94.2}_{-6.2}^{+5.6}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ . We emphasize that the H 0 measurement depends sensitively on the ${\mathrm{DM}}_{\mathrm{halo}}^{\mathrm{MW}}$ prior. Since flat ΛCDM has one more free parameter, R h = ct is favored by the Bayesian Information Criterion (BIC) with a likelihood of ~73% versus ~27%. Through simulations, we find that if the real cosmology is ΛCDM, a sample of ~1150 FRBs in the redshift range 0 &lt; z &lt; 3 would be sufficient to rule out R h = ct at a 3σ confidence level, while ~550 FRBs would be necessary to rule out ΛCDM if the real cosmology is instead R h = ct. The required sample sizes are different, reflecting the fact that the BIC imposes a severe penalty on the model with more free parameters. We further adopt a straightforward method of deriving an upper limit to H 0, without needing to consider the poorly known probability distribution of the DM contributed by the host galaxy. The theoretical DM contribution from the intergalactic medium (DMIGM) at any z is proportional to H 0. Thus, requiring the extragalactic DMext to be larger than DMIGM delimits H 0 to the upside. Assuming flat ΛCDM, we have H 0 &lt; 89.0 km s-1 Mpc-1 at a 95% confidence level.

Keywords: Radio transient sources, Cosmological models, Observational cosmology, Cosmological parameters
AstroSat View of the Neutron Star Low-mass X-Ray Binary GX 340+0. Understanding the spectral evolution along the "Z"-shaped track in the hardness-intensity diagram of Z sources, which are a class of luminous neutron star low-mass X-ray binaries, is crucial to probe accretion processes close to the neutron star. Here, we study the horizontal branch (HB) and the normal branch (NB) of the Z source GX 340+0 using AstroSat data. We find that the HB and the NB appear as two different types of X-ray intensity dips, which can appear in any sequence and with various depths. Our 0.8-25 keV spectra of dips and the hard apex can be modeled by the emissions from an accretion disk, a Comptonizing corona covering the inner disk, and the neutron star surface. We find that as the source moves onto the HB, the corona is replenished and energized by the disk and a reduced amount of disk matter reaches the neutron star surface. We also conclude that quasiperiodic oscillations during HB/NB are strongly associated with the corona and explain the evolution of strength and hard lag of this timing feature using the estimated coronal optical depth evolution.

Keywords: Accretion, X-ray binary stars, Stellar accretion disks
CHANDRA X-Ray Observations of A119: Cold Fronts and a Shock in an Evolved Off-axis Merger. We present Chandra X-ray observations of the dynamically complex galaxy cluster A119 (z = 0.044). A119 is host to two narrow-angle-tail (NAT) radio sources (0053-015 and 0053-016), whose tails are oriented parallel to each other, despite orthogonally oriented jet axes. Imaging and spectral analysis reveal X-ray emission elongated along the NE-SW axis, along with the presence of complex structures, including surface brightness discontinuities, which suggest possible merger activity along this axis. From radial profiles of the X-ray surface brightness, temperature, pressure, and density, we identify two surface brightness edges that are found to be cold fronts, possibly associated with large-scale sloshing of intracluster medium gas. We also identify a brightness edge to the S that is found to be a shock front with Mach number M = 1.21 ± 0.11, consistent with a merger shock. In addition, previous optical studies show the alignment of optical substructures along the N-S direction. The elongated X-ray emission, orientations of the NAT tails, and alignment of the optical substructure all suggest recent or ongoing merger activity in the NE-SW direction.

Keywords: Galaxy clusters, Intracluster medium
A High-mass, Young Star-forming Core Escaping from Its Parental Filament. We studied the unique kinematic properties in massive filament G352.63-1.07 at 103 au spatial scale with the dense molecular tracers observed with the Atacama Large Millimeter/submillimeter Array. We find the central massive core M1 (12 M ⊙) being separated from the surrounding filament with a velocity difference of $v-{\overline{v}}_{\mathrm{sys}}=-2\,\mathrm{km}\,{{\rm{s}}}^{-1}$ and a transverse separation within 3″. Meanwhile, as shown in multiple dense-gas tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament toward both its ends. M1 thus represents a very beginning state for a massive, young star-forming core escaping from the parental filament, within a timescale of ~4000 yr. Based on its kinetic energy (3.5 × 1044 erg), the core escape is unlikely solely due to the original filament motion or magnetic field but requires more energetic events such as a rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental turbulence. This may help the filament to become stabilized again.

Keywords: Interstellar filaments, Dense interstellar clouds, Young stellar objects, Star formation, Gravitational collapse
Comprehensive Radiative MHD Simulations of Eruptive Flares above Collisional Polarity Inversion Lines. We present a new simulation setup using the MURaM radiative MHD code that allows the study of the formation of collisional polarity inversion lines (cPILs) in the photosphere and the coronal response including flares. In this scheme, we start with a bipolar sunspot configuration and set the spots on collision course by imposing the appropriate velocity field at the footpoints in the subphotospheric boundary. We produce different setups with the same initial spot separation by varying physical parameters such as the collision speed and minimum collision distance. While all setups lead to the formation of an EUV and X-ray sigmoid structure, only the cases with a close passing of the spots cause flares and mass eruptions. The energy release is in the 1-2 × 1031 erg range, putting the simulated flares into the upper C-class to lower M-class range of GOES X-ray 1-8 Å flux. While the setup with the more distant passing of the spots does not lead to a flare, the corona is nonetheless substantially heated, suggesting noneruptive energy-release mechanisms. We focus our discussion on two particular setups that differ in spot coherence and resulting cPIL length persistence. We find different timings in the transition from a sheared magnetic arcade to magnetic flux rope (MFR); the setup with a large length but shorter duration cPIL produces a MFR during the eruption, while the MFR is preexisting in the setup with a large length and longer duration cPIL. While both result in flares of comparable strength and the eruption of a coronal mass ejection, the setup with preexisting MFR (and embedded filament) leads to an MFR eruption with a larger mass content.

Keywords: Solar active region magnetic fields, Radiative magnetohydrodynamics, Solar flares, Solar photosphere, Solar active regions, Solar coronal mass ejections, Active solar corona
UV-bright Star-forming Clumps and Their Host Galaxies in UVCANDELS at 0.5 ≤ z ≤ 1. Giant star-forming clumps are a prominent feature of star-forming galaxies (SFGs) and contain important clues on galaxy formation and evolution. However, the basic demographics of clumps and their host galaxies remain uncertain. Using the Hubble Space Telescope/Wide Field Camera 3 F275W images from the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we detect and analyze giant star-forming clumps in galaxies at 0.5 ≤ z ≤ 1, connecting two epochs when clumps are common (at cosmic high noon, z ~ 2) and rare (in the local Universe). We construct a clump sample whose rest-frame 1600 Å luminosity is 3 times higher than the most luminous local H II regions (M UV ≤ -16 AB). In our sample, 35% ± 3% of low-mass galaxies (log[M ∗/M ⊙] &lt; 10) are clumpy (i.e., containing at least one off-center clump). This fraction changes to 22% ± 3% and 22% ± 4% for intermediate (10 ≤ log[M ∗/M ⊙] ≤ 10.5) and high-mass (log[M ∗/M ⊙] &gt; 10.5) galaxies, in agreement with previous studies. When compared to similar-mass nonclumpy SFGs, low- and intermediate-mass clumpy SFGs tend to have higher star formation rates (SFRs) and bluer rest-frame U - V colors, while high-mass clumpy SFGs tend to be larger than nonclumpy SFGs. However, clumpy and nonclumpy SFGs have similar Sérsic index, indicating a similar underlying density profile. Furthermore, we investigate how the UV luminosity of star-forming regions correlates with the physical properties of host galaxies. On average, more luminous star-forming regions reside in more luminous, smaller, and/or higher specific SFR galaxies and are found closer to their hosts' galactic centers.

Keywords: Starburst galaxies, Galaxy formation, Galaxy properties, Star forming regions, Galaxy structure, Galaxy evolution
Things That Might Go Bump in the Night: Assessing Structure in the Binary Black Hole Mass Spectrum. Several features in the mass spectrum of merging binary black holes (BBHs) have been identified using data from the Third Gravitational Wave Transient Catalog (GWTC-3). These features are of particular interest as they may encode the uncertain mechanism of BBH formation. We assess if the features are statistically significant or the result of Poisson noise due to the finite number of observed events. We simulate catalogs of BBHs whose underlying distribution does not have the features of interest, apply the analysis previously performed on GWTC-3, and determine how often such features are spuriously found. We find that one of the features found in GWTC-3, the peak at ~35 M ☉, cannot be explained by Poisson noise alone: peaks as significant occur in 1.7% of catalogs generated from a featureless population. This peak is therefore likely to be of astrophysical origin. The data is suggestive of an additional significant peak at ~10 M ☉, though the exact location of this feature is not resolvable with current observations. Additional structure beyond a power law, such as the purported dip at ~14 M ☉, can be explained by Poisson noise. We also provide a publicly available package, GWMockCat, that creates simulated catalogs of BBH events with correlated measurement uncertainty and selection effects according to user-specified underlying distributions and detector sensitivities.

Keywords: Bayesian statistics, Black holes, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Hierarchical models, Astrophysical black holes
Constraining Thermal Emission of Pluto's Haze from Infrared Rotational Lightcurves. The rotational lightcurves of the Pluto-Charon system were previously believed to be solely attributed to their surfaces. However, a proposed scenario of haze cooling suggests that the atmospheric haze of Pluto could significantly contribute to mid-infrared emission, which calls for a revisit of previous analyses. In this study, we employ a Bayesian retrieval approach to constrain the haze emission from the rotational lightcurves of the Pluto-Charon system. The lightcurves were observed by the Spitzer and Herschel telescopes at 24 and 70 μm, and were combined with the latest surface albedo maps of Pluto and Charon from the New Horizons spacecraft. Our results show that including the haze emission is consistent with all current observations, with the best-fit haze flux around 1.63 mJy. This is in agreement with the composition of Titan-like tholins. However, the "surface only" scenario, which excludes the haze contribution, can still explain the observations. We conclude that the current data at 24 μm cannot constrain Pluto's haze emission due to the degeneracy with Charon's surface emission. Regardless, some surface properties of Pluto are well constrained by the shape of the lightcurves, with a thermal inertia of approximately 8-10 MKS and a relatively low CH4 emissivity of 0.3-0.5. We suggest that observations by the JWST telescope at 18 μm, which can resolve Pluto from Charon, could directly probe the haze emission of Pluto due to the low surface emission at that wavelength.

Keywords: Pluto
Formation of Inner Planets in the Presence of a Cold Jupiter: Orbital Evolution and Relative Velocities of Planetesimals. We investigate the orbital evolution of planetesimals in the inner disk in the presence of nebula gas and a (proto-) cold Jupiter. By varying the mass, eccentricity, and semimajor axis of the planet, we study the dependence of the relative velocities of the planetesimals on these parameters. For classic small planetesimals (1016-1020 g) whose mutual gravitational interaction is negligible, gas drag introduces a size-dependent alignment of orbits and keeps the relative velocity low for similar-sized bodies, while preventing orbital alignment for different-sized planetesimals. Regardless of the location and the mass ratio of the planetesimals, increasing the mass and eccentricity or decreasing the orbital distance of the planet always lead to higher relative velocities of the planetesimals. However, for massive planetesimals, the interplay of viscous stirring, gas damping, and secular perturbation results in the lower velocity dispersion of equal-sized planetesimals when the planet is more massive or when it is located on a closer or more eccentric orbit. The random velocities of such planetesimals remain almost unperturbed when the planet is located beyond Jupiter's current orbit or when it is less massive or less eccentric than Jupiter. Unlike small planetesimals, such large planetesimals can grow in a runaway fashion, as in the unperturbed case. Our results imply that the presence of a cold Jupiter does not impede the formation of inner rocky planets through planetesimal accretion, provided that the planetesimals are initially large.

Keywords: Orbital evolution, Planetary dynamics, Planet formation, Planetesimals
The Division between Weak and Strong Explosions from Failed Supernovae. Some massive stars likely fail to produce core-collapse supernovae, but these failed supernovae (FSNe) can generate an electromagnetic outburst prior to the disappearance of the star, as the mass lost to neutrinos during the stellar core collapse results in the formation and breakout of a second shock. We show that, when the mass lost to neutrinos is sufficiently small, there are two self-similar solutions that describe the propagation of a weak shock into a hydrodynamically expanding envelope that simultaneously yield accretion onto the black hole. The larger Mach number solution is unstable and yields the minimum Mach number that a shock must have to strengthen into the energy-conserving regime. Above a critical mass loss, there are no weak-shock solutions, implying that there are only strong explosions if the neutrino mass loss is above a critical value, and this value is a few percent of the mass of the star (and is physically achievable) for typical parameters. Our results imply that the fate of the explosion from an FSN-weak with little to no mass ejection or strong with the expulsion of the majority of the envelope-is a sensitive function of the stellar properties and the neutrino mass loss. We also show that there is a second type of self-similar solution for the shock that results in the settling of the gas near the compact object, which may be applicable to nonterminal stellar eruptions and the response of a gaseous disk to gravitational-wave induced mass loss from a binary black hole merger.

Keywords: Analytical mathematics, Shocks, Hydrodynamics, Core-collapse supernovae