Sazuna/UAT_keywords huggingface dataset:
Testing Evolution of LFQPOs with Mass Accretion Rate in GRS 1915+105 with Insight-HXMT. Using the Insight-HXMT observations of GRS 1915+105 when it exhibits low-frequency quasiperiodic oscillations (QPOs), we measure the evolution of the QPO frequency along with disk inner radius and mass accretion rate. We find a tight positive correlation between the QPO frequency and mass accretion rate. Our results extend the finding of previous work with AstroSat to a larger range of accretion rates with independent instruments and observations. Treating the QPO frequency of GRS 1915+105 as the relativistic dynamic frequency of a truncated disk, we are able to confirm the high spin nature of the black hole in GRS 1915+105. We also address the potential of our finding to test general relativity in the future.

Keywords: X-ray astronomy, Stellar mass black holes, High energy astrophysics, Compact objects
Detection of Tidal Disruption Events around Direct-collapse Black Holes at High Redshifts with the James Webb Space Telescope. This is the third sequel in a series discussing the discovery of various types of extragalactic transients with the James Webb Space Telescope (JWST) in a narrow-field (∼0.1 deg2), moderately deep (mAB ∼ 27 mag) survey. In this part we focus on the detectability and observational characteristics of direct-collapse black holes (DCBHs) and tidal disruption events (TDEs) around them. We use existing models for DCBH accretion luminosities and spectra, as well as for TDE light curves, and find that accreting DCBH seeds may be bright enough for detection up to z ∼ 7 with JWST NIRCam imaging. TDEs of massive (M ≳ 50 M⊙) stars around them can enhance the chance for discovering them as transient objects, although the rate of such events is low, a few per survey time. TDEs around nonaccreting black holes of M ∼ 106 M⊙ may also be detected at z &lt; 7 redshifts in the redder NIRCam bands between 3 and 5 μs. It is also shown that accreting DCBHs appear separate from supernovae on the NIRCam color-color plot, but TDEs from quiescent black holes fall in nearly the same color range as superluminous supernovae, which makes them more difficult to identify.

Keywords: Surveys, Early universe, Reionization, Black holes
Gravitational Wave in f(R) Gravity: Possible Signature of Sub- and Super-Chandrasekhar Limiting-mass White Dwarfs. After the prediction of many sub- and super-Chandrasekhar (at least a dozen for the latter) limiting-mass white dwarfs (WDs), hence apparently a peculiar class of WDs, from the observations of luminosity of Type Ia supernovae, researchers have proposed various models to explain these two classes of WD separately. We earlier showed that these two peculiar classes of WD, along with the regular WD, can be explained by a single form of the f(R) gravity, whose effect is significant only in the high-density regime, and it almost vanishes in the low-density regime. However, since there is no direct detection of such a WD, it is difficult to single out one specific theory from the zoo of modified theories of gravity. We discuss the possibility of direct detection of such a WD in gravitational wave (GW) astronomy. It is well known that in f(R) gravity more than two polarization modes are present. We estimate the amplitudes of all the relevant modes for the peculiar and the regular WD. We further discuss the possibility of their detections through future-based GW detectors, such as LISA, ALIA, DECIGO, BBO, or the Einstein Telescope, and thereby put constraints on or rule out various modified theories of gravity. This exploration links the theory with possible observations through GW in f(R) gravity.

Keywords: Rotation powered pulsars, Scalar-tensor-vector gravity, White dwarf stars, Stellar magnetic fields, Chandrasekhar limit, Gravitational waves, Stellar surfaces
Computing Helioseismic Sensitivity Kernels for the Sun's Large-scale Internal Flows Using Global-scale Wave-propagation Simulations. Helioseismic waves observable at the solar surface can be used to probe the properties of the Sun's interior. By measuring helioseismic travel times between different location on the surface, flows and other interior properties can be inferred using so-called sensitivity kernels that relate the amount of travel-time shift with variations in interior properties. In particular, sensitivity kernels for flows have been developed in the past, using either ray or Born approximation, and have been used to infer solar interior flows such as the meridional circulation, which is of particular interest for understanding the structure and dynamics of the Sun. Here we introduce a new method for deriving three-dimensional sensitivity kernels for large-scale horizontal flows in the solar interior. We perform global-Sun wave-propagation simulations through 784 small flow perturbations placed individually in the interior of a simulated Sun, and measure the shifts in helioseismic travel times caused by these perturbations. Each measurement corresponds to a linear equation connecting the flow perturbation velocities and the sensitivity kernels. By solving the resulting large set of coupled linear equations, we derive three-dimensional sensitivity kernels for horizontal flows, which have a longitudinal component (parallel to the wave's travel direction) and a transverse component (perpendicular to the wave's travel direction). The kernels exhibit a "banana" shape, similar to kernels derived using Born-approximation methods, and show that transverse components are not negligible in inversions for interior flows.

Keywords: Helioseismology, Computational methods, Solar oscillations, Solar interior
FANTASY: User-friendly Symplectic Geodesic Integrator for Arbitrary Metrics with Automatic Differentiation. We present FANTASY (Finally A Numerical Trajectory Algorithm both Straightforward and sYmplectic), a user-friendly, open-source symplectic geodesic integrator written in Python. FANTASY is designed to work "out of the box" and does not require anything from the user aside from the metric and the initial conditions for the geodesics. FANTASY efficiently computes derivatives up to machine precision using automatic differentiation, allowing the integration of geodesics in arbitrary space(times) without the need for the user to manually input Christoffel symbols or any other metric derivatives. Further, FANTASY utilizes a Hamiltonian integration scheme that doubles the phase space, where two copies of the particle phase space are evolved together. This technique allows for an integration scheme that is both explicit and symplectic, even when the Hamiltonian is not separable. FANTASY comes prebuilt with second- and fourth-order schemes, and is easily extendable to higher-order schemes. FANTASY also includes an automatic Jacobian calculator that allows for coordinate transformations to be done automatically.

Keywords: Publicly available software, Black holes, Astronomy software, Gravitation, Orbits, General relativity, Geodesics
State-switching Mechanism of Intermittent Pulsars. The emission feature of intermittent pulsars is significant for understanding the pulsar emission mechanism. Using the observational evidence of radio emissions turning on and off and the corresponding spin-down rates in these two states of an intermittent pulsar, we will examine the polar-cap potential drop, gap height, and curvature radii of a few intermittent pulsars within the regime of the pulsar polar-cap emission theory by applying the current loss and energy flux of particle flow to pulsar braking, which are generally associated with radio emission from the polar cap. It is seen that the polar-cap parameters of the intermittent pulsars are almost equal to their maximum values, which is the main prediction of the pulsar polar-cap theory with respect to the breaking of the radio emission. It is also noticed that the intermittent pulsars are distributed near the dipole death line in the $P\mbox{--}\dot{P}$ diagram, which is consistent with their emission features and the calculated polar-cap parameters. To further confirm the state switching of the intermittent pulsar, the relationships among spin-down rate, gap height, potential drop, and activity duty cycles of PSR B1931+24 are discussed. It is found that the gap height has an anticorrelation with the activity duty cycle, which indicates that the intermittency of the radio emission has a close connection to the gap height, as indicated by the pulsar polar-cap emission theory.

Keywords: Neutron stars, Pulsars
Finite System-size Effects in Self-organized Criticality Systems. We explore upper limits for the largest avalanches or catastrophes in nonlinear energy dissipation systems governed by self-organized criticality. We generalize the idealized "straight" power-law size distribution and Pareto distribution functions in order to accommodate incomplete sampling, limited instrumental sensitivity, finite system-size effects, and "Black Swan" and "Dragon King" extreme events. Our findings are as follows. (i) Solar flares show no finite system-size limits up to L ≲ 200 Mm, but solar flare durations reveal an upper flare duration limit of ≲6 hr. (ii) Stellar flares observed with Kepler exhibit inertial ranges of E ≈ 1034-1037 erg, finite system-size ranges of E ≈ 1037-1038 erg, and extreme events at E ≈ (1-5) × 1038 erg. (iii) The maximum flare energies of different spectral type stars (M, K, G, F, A, giants) reveal a positive correlation with the stellar radius, which indicates a finite system-size limit imposed by the stellar surface area. Fitting our finite system-size models to terrestrial data sets (earthquakes, wildfires, city sizes, blackouts, terrorism, words, surnames, web links) yields evidence (in half of the cases) for finite system-size limits and extreme events, which can be modeled with dual power-law size distributions.

Keywords: Stellar phenomena, Astrostatistics distributions, Solar flares, Stellar flares
External Enrichment of Mini Halos by the First Supernovae. Recent high-resolution simulations of early structure formation have shown that externally enriched halos may form some of the first metal-enriched stars. This study utilizes a 1 comoving Mpc3 high-resolution simulation to study the enrichment process of metal-enriched halos down to z = 9.3. Our simulation uniquely tracks the metals ejected from Population III stars, and we use this information to identify the origin of metals within metal-enriched halos. These halos show a wide range of metallicities, but we find that the source of metals for ≳50% of metal-enriched halos is supernova explosions of Population III stars occurring outside their virial radii. The results presented here indicate that external enrichment by metal-free stars dominates the enrichment process of halos with virial mass below 106 M⊙ down to z = 9.3. Despite the prevalence of external enrichment in low-mass halos, Population II stars forming due to external enrichment are rare because of the small contribution of low-mass halos to the global star formation rate combined with low metallicities toward the center of these halos resulting from metal ejecta from external sources mixing from the outside in. The enriched stars that do form through this process have absolute metallicities below 10-3 Z⊙. We also find that the fraction of externally enriched halos increases with time: ∼90% of halos that are externally enriched have Mvir &lt; 106 M⊙, and that pair-instability supernovae contribute the most to the enrichment of the intergalactic medium as a whole and are thus are the predominant supernova type contributing to the external enrichment of halos.

Keywords: Primordial galaxies
Shocks and Molecules in Diffuse Interstellar Cloud Pairs. The diffuse interstellar medium (ISM) is dynamic, and its chemistry and evolution are determined by shock fronts as well as photodissociation. Shocks are implied by the supersonic motions and velocity dispersion, often statistically called "turbulence". We compare models of magnetohydrodynamic (MHD) shocks, with speeds typical of cloud motions through the ISM (3-25 km s-1) and densities typical of cold neutral gas (∼102 cm-3), to archival observations of the H I 21 cm line for gas kinematics, far-infrared emission for dust mass, and mid-infrared emission for high-resolution morphology, to identify shock fronts in three high-latitude cloud pairs with masses of order 50 M⊙. The clouds have "heads" with extended "tails," and high-resolution images show arcs on the leading edges of the "heads" that could be individual shocks. The H I shows higher-velocity gas at the leading edges due to shock-accelerated material. For two cloud pairs, one cloud has an active shock indicated by broad and offset H I, while the other cloud has already been shocked and is predominantly "CO-dark" H2. Two-dimensional MHD simulations for shocks parallel to the magnetic field for pairs of clouds show a remarkable similarity to observed cloud features, including merged "tails" due to aligned flow and magnetic field, which leads to lateral confinement downstream. A parallel alignment between magnetic field and gas flow may lead to formation of small molecular clouds.

Keywords: Shocks, H I line emission, Diffuse molecular clouds, Diffuse interstellar clouds
On the Origin of Solar Hemispherical Helicity Rules: Simulations of the Rise of Magnetic Flux Concentrations in a Background Field. Solar active regions and sunspots are believed to be formed by the emergence of strong toroidal magnetic flux from the solar interior. Modeling of such events has focused on the dynamics of compact magnetic entities, colloquially known as "flux tubes," often considered to be isolated magnetic structures embedded in an otherwise field-free environment. In this paper, we show that relaxing such idealized assumptions can lead to surprisingly different dynamics. We consider the rise of tube-like flux concentrations embedded in a large-scale volume-filling horizontal field in an initially quiescent adiabatically stratified compressible fluid. In a previous letter, we revealed the unexpected major result that concentrations whose twist is aligned with the background field at the bottom of the tube are more likely to rise than the opposite orientation (for certain values of parameters). This bias leads to a selection rule which, when applied to solar dynamics, is in agreement with the observations known as the solar hemispheric helicity rule(s) (SHHR). Here, we examine this selection mechanism in more detail than was possible in the earlier letter. We explore the dependence on parameters via simulations, delineating the Selective Rise Regime, where the bias operates. We provide a theoretical model to predict and explain the simulation dynamics. Furthermore, we create synthetic helicity maps from Monte Carlo simulations to mimic the SHHR observations, and to demonstrate that our mechanism explains the observed scatter in the rule, as well as its variation over the solar cycle.

Keywords: Magnetohydrodynamics, Solar interior, Sunspots, Solar dynamo, Solar magnetic fields
Properties of Compact Faint Radio Sources as a Function of Angular Size from Stacking. The polarization properties of radio sources powered by an Active Galactic Nucleus (AGN) have attracted considerable attention because of the significance of magnetic fields in the physics of these sources, their use as probes of plasma along the line of sight, and as a possible contaminant of polarization measurements of the cosmic microwave background. For each of these applications, a better understanding of the statistics of polarization in relation to source characteristics is crucial. In this paper, we derive the median fractional polarization, Π0,med, of large samples of radio sources with 1.4 GHz flux density 6.6 &lt; S1.4 &lt; 70 mJy, by stacking 1.4 GHz NVSS polarized intensity as a function of angular size derived from the FIRST survey. Five samples with deconvolved mean angular size 1"8 to 8"2 and two samples of symmetric double sources are analyzed. These samples represent most sources smaller than or near the median angular size of the mJy radio source population We find that the median fractional polarization Π0,med at 1.4 GHz is a strong function of source angular size ≲5″ and a weak function of angular size for larger sources up to ∼8″. We interpret our results as depolarization inside the AGN host galaxy and its circumgalactic medium. The curvature of the low-frequency radio spectrum is found to anticorrelate with Π0,med, a further sign that depolarization is related to the source.

Keywords: Radio jets, Extragalactic radio sources, Radio galaxies, Spectral index, Polarimetry, Extragalactic magnetic fields
The Dragonfly Wide Field Survey. II. Accurate Total Luminosities and Colors of Nearby Massive Galaxies and Implications for the Galaxy Stellar-mass Function. Stellar-mass estimates of massive galaxies are susceptible to systematic errors in their photometry, due to their extended light profiles. In this study, we use data from the Dragonfly Wide Field Survey to accurately measure the total luminosities and colors of nearby massive galaxies. The low surface brightness limits of the survey (μg ≈ 31 mag arcsec-2 on a 1' scale) allow us to implement a method, based on integrating the 1D surface brightness profile, that is minimally dependent on any parameterization. We construct a sample of 1188 massive galaxies with $\mathrm{log}{M}_{* }/{M}_{\odot }\gt 10.75$ based on the Galaxy Mass and Assembly (GAMA) survey and measure their total luminosities and g - r colors. We then compare our measurements to various established methods applied to imaging from the Sloan Digital Sky Survey (SDSS), focusing on those favored by the GAMA survey. In general, we find that galaxies are brighter in the r band by an average of ∼0.05 mag and bluer in g - r colors by ∼0.06 mag compared to the GAMA measurements. These two differences have opposite effects on the stellar-mass estimates. The total luminosities are larger by 5% but the mass-to-light ratios are lower by ∼10%. The combined effect is that the stellar-mass estimate of massive galaxies decreases by 7%. This, in turn, implies a small change in the number density of massive galaxies: ≤30% at $\mathrm{log}{M}_{* }/{M}_{\odot }\geqslant 11$ .

Keywords: Galaxy colors, Galaxy photometry, Galaxy luminosities, Galaxy counts
New Growth Mechanism of Dust Grains in Protoplanetary Disks with Magnetically Driven Disk Winds. We discovered a new growth mode of dust grains to kilometer-size bodies in protoplanetary disks that evolve via viscous accretion and magnetically driven disk winds (MDWs). We solved an approximate coagulation equation of dust grains with time-evolving disks that consist of both gas and solid components using a one-dimensional model. With grain growth, all solid particles initially drift inward toward the central star due to the gas drag force. However, the radial profile of gas pressure, P, is modified by the MDW that disperses the gas in an inside-out manner. Consequently, a local concentration of solid particles is created by the converging radial flux of drifting dust grains at the location with a convex-upward profile of P. When the dimensionless stopping time, St, exceeds unity there, the solid particles spontaneously reach the growth-dominated state because of the positive feedback between the suppressed radial drift and the enhanced accumulation of dust particles that drift from the outer part. Once the solid particles are in the drift-limited state, the above-mentioned condition of St $\gtrsim \,1$ for dust growth is equivalent to Σd/Σg ≳ η, where Σd/Σg is the dust-to-gas surface-density ratio and η is the dimensionless radial pressure-gradient force. As a consequence of the successful growth of dust grains, a ring-like structure containing planetesimal-size bodies is formed at the inner part of the protoplanetary disks. Such a ring-shaped concentration of planetesimals is expected to play a vital role in the subsequent planet formation.

Keywords: Planetary system formation, Protoplanetary disks, Planet formation, Planetesimals
Jet Collimation and Acceleration in the Giant Radio Galaxy NGC 315. We study the collimation and acceleration of jets in the nearby giant radio galaxy NGC 315, using multifrequency Very Long Baseline Array observations and archival High Sensitivity Array and Very Large Array data. We find that the jet geometry transitions from a semi-parabolic shape into a conical/hyperbolic shape at a distance of ≈105 gravitational radii. We constrain the frequency-dependent position of the core, from which we locate the jet base. The jet collimation profile in the parabolic region is in good agreement with the steady axisymmetric force-free electrodynamic solution for the outermost poloidal magnetic field line anchored to the black hole event horizon on the equatorial plane, similar to the nearby radio galaxies M87 and NGC 6251. The velocity field derived from the asymmetry in brightness between the jet and counterjet shows gradual acceleration up to the bulk Lorentz factor of Γ ∼ 3 in the region where the jet collimation occurs, confirming the presence of the jet acceleration and collimation zone. These results suggest that the jets are collimated by the pressure of the surrounding medium and accelerated by converting Poynting flux to kinetic energy flux. We discover limb brightening of the jet in a limited distance range where the angular resolution of our data is sufficient to resolve the jet transverse structure. This indicates that either the jet has a stratified velocity field of fast-inner and slow-outer layers or the particle acceleration process is more efficient in the outer layer owing to the interaction with the surroundings on parsec scales.

Keywords: Accretion, Very long baseline interferometry, Relativistic jets, Radio galaxies, Active galactic nuclei, Magnetic fields
The Similarity of Abundance Ratio Trends and Nucleosynthetic Patterns in the Milky Way Disk and Bulge. We compare abundance ratio trends in a sample of ∼11,000 Milky Way bulge stars (RGC &lt; 3 kpc) from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to those of APOGEE stars in the Galactic disk (5 kpc &lt; RGC &lt; 11 kpc). We divide each sample into low-Ia (high-[Mg/Fe]) and high-Ia (low-[Mg/Fe]) populations, and in each population, we examine the median trends of [X/Mg] versus [Mg/H] for elements X = Fe, O, Na, Al, Si, P, S, K, Ca, V, Cr, Mn, Co, Ni, Cu, and Ce. To remove small systematic trends of APOGEE abundances with stellar $\mathrm{log}(g)$ , we resample the disk stars to match the $\mathrm{log}(g)$ distributions of the bulge data. After doing so, we find nearly identical median trends for low-Ia disk and bulge stars for all elements. High-Ia trends are similar for most elements, with noticeable (0.05-0.1 dex) differences for Mn, Na, and Co. The close agreement of abundance trends (with typical differences ≲0.03 dex) implies that similar nucleosynthetic processes enriched bulge and disk stars despite the different star formation histories and physical conditions of these regions. For example, we infer that differences in the high-mass slope of the stellar initial mass function between disk and bulge must have been ≲0.30. This agreement, and the generally small scatter about the median sequences, means that one can predict all of a bulge star's APOGEE abundances with good accuracy knowing only its measured [Mg/Fe] and [Mg/H] and the observed trends of disk stars.

Keywords: Explosive nucleosynthesis, Nucleosynthesis, Stellar abundances, Chemical abundances, Galactic bulge, Stellar nucleosynthesis, Galactic abundances