Sazuna/UAT_keywords huggingface dataset:
A Novel Solution for Resonant Scattering Using Self-consistent Boundary Conditions. We present two novel additions to the semianalytic solution of Lyα radiative transfer in spherical geometry: (1) implementation of the correct boundary condition for a steady source, and (2) solution of the time-dependent problem for an impulsive source. For the steady-state problem, the solution can be represented as a sum of two terms: a previously known analytic solution of the equation with mean intensity J = 0 at the surface, and a novel, semianalytic solution which enforces the correct boundary condition of zero-ingoing intensity at the surface. This solution is compared to that of the Monte Carlo method, which is valid at arbitrary optical depth. It is shown that the size of the correction is of order unity when the spectral peaks approach the Doppler core and decreases slowly with line center optical depth, specifically as ${(a{\tau }_{0})}^{-1/3}$ , which may explain discrepancies seen in previous studies. For the impulsive problem, the time, spatial, and frequency dependence of the solution are expressed using an eigenfunction expansion in order to characterize the escape time distribution and emergent spectra of photons. It is shown that the lowest-order eigenfrequency agrees well with the decay rate found in the Monte Carlo escape time distribution at sufficiently large line center optical depths. The characterization of the escape time distribution highlights the potential for a Monte Carlo acceleration method, which would sample photon escape properties from distributions rather than calculating every photon scattering, thereby reducing computational demand.

Keywords: Radiative transfer equation, Radiative transfer, Exoplanet atmospheres
Quantifying Properties of Photospheric Magnetic Cancellations in the Quiet Sun Internetwork. We analyzed spectropolarimetric data from the Swedish 1 m Solar Telescope to investigate the physical properties of small-scale magnetic cancellations in the quiet Sun photosphere. Specifically, we looked at the full Stokes polarization profiles along the Fe I 557.6 nm and of the Fe I 630.1 nm lines measured by the CRisp Imaging SpectroPolarimeter to study the temporal evolution of the line-of-sight magnetic field during 42.5 minutes of quiet Sun evolution. From this magnetogram sequence, we visually identified 38 cancellation events. We then used the Yet Another Feature Tracking Algorithm to characterize the physical properties of these magnetic cancellations. We found on average 1.6 × 1016 Mx of magnetic flux canceled in each event with an average cancellation rate of 3.8 × 1014 Mx s-1. The derived canceled flux is associated with strong downflows, with an average speed of V LOS ≈ 1.1 km s-1. Our results show that the average lifetime of each event is 9.2 minutes with an average of 44.8% of initial magnetic flux being canceled. Our estimates of magnetic fluxes provide a lower limit since studied magnetic cancellation events have magnetic field values that are very close to the instrument noise level. We observed no horizontal magnetic fields at the cancellation sites and therefore cannot conclude whether the events are associated with structures that could cause magnetic reconnection.

Keywords: Solar magnetic flux emergence, Solar photosphere, The Sun, Solar surface, Solar physics, Solar magnetic fields
Is Fermi 1544-0649 a Misaligned Blazar? Discovering the Jet Structure with Very Long Baseline Interferometry. Fermi J1544-0649 is a transient GeV source first detected during its GeV flares in 2017. Multiwavelength observations during the flaring time demonstrate variability and spectral energy distributions that are typical of a blazar. Other than the flare time, Fermi J1544-0649 is quiet in the GeV band and has looked rather like a quiet galaxy (2MASX J15441967-0649156) for a decade. Together with the broad absorption-lines-like feature we further explore the "misaligned blazar scenario." We analyzed the Very Long Baseline Array (VLBA) and East Asian VLBI Network (EAVN) data from 2018 to 2020 and discovered the four jet components from Fermi J1544-0649. We found a viewing angle around 3.°7 to 7.°4. The lower limit of the viewing angle indicates a blazar with an extreme low duty cycle of gamma-ray emission; the upper limit of it supports the "misaligned blazar scenario." Follow-up multiwavelength observations after 2018 show Fermi J1544-0649 remains quiet in GeV, X-ray, and optical bands. A multimessenger search of neutrinos is also performed, and an excess of 3.1σ significance is found for this source.

Keywords: Neutrino astronomy, Radio jets, High energy astrophysics
On the Energy Dispersion of Magnetic Rossby Waves. The energy dispersion of magnetic Rossby waves has been investigated by applying the two-dimensional incompressible magnetohydrodynamic (MHD) equations in both uniform basic flow and basic magnetic field. The dispersion relation suggests that the magnetic Rossby waves can be divided into fast- and slow-propagating modes, respectively. The fast-propagating mode propagates eastward and is similar to the fast Alfvén waves. The energy dispersion speed is faster than the phase speed, which means the perturbation energy can lead the perturbations themselves to arrive downstream. The slow-propagating waves with smaller (larger) horizontal scales are similar to those of the slow Alfvén waves (Rossby waves). The zonal group velocity is slower than the zonal phase speed for the slow-propagating magnetic Rossby waves. For the slow-propagating waves that propagate eastward, this means that the perturbation energy may trigger new perturbations that are located upstream of the perturbations themselves. The group velocity vector is basically same as (opposite of) the wavevector for the fast-propagating (slow-propagating) magnetic Rossby waves that propagate eastward. The endpoints of the group velocity vectors and the wavevector multiplying a factor are located on a cycle in the wavenumber space. Due to the uniform basic flow and the uniform basic magnetic field, the energy dispersion paths (called rays) are straight lines. Along the straight-line rays, the wave action, wave energy, and amplitude keep their initial values, and the wave neither develops nor decays.

Keywords: Internal waves, Magnetohydrodynamics, Planetary atmospheres, Solar atmospheric motions, Astrophysical fluid dynamics
On the Energy Dependence of Galactic Cosmic Ray Anisotropies in the Very Local Interstellar Medium. We report on the energy dependence of Galactic cosmic rays (GCRs) in the very local interstellar medium (VLISM) as measured by the Low Energy Charged Particle (LECP) instrument on the Voyager 1 spacecraft. The LECP instrument includes a dual-ended solid-state detector particle telescope mechanically scanning through 360° across eight equally spaced angular sectors. As reported previously, LECP measurements showed a dramatic increase in GCR intensities for all sectors of the ≥211 MeV count rate (CH31) at the Voyager 1 heliopause (HP) crossing in 2012; however, since then the count rate data have demonstrated systematic episodes of intensity decrease for particles around 90° pitch angle. To shed light on the energy dependence of these GCR anisotropies over a wide range of energies, we use Voyager 1 LECP count rate and pulse height analyzer (PHA) data from ≥211 MeV channel together with lower-energy LECP channels. Our analysis shows that, while GCR anisotropies are present over a wide range of energies, there is a decreasing trend in the amplitude of second-order anisotropy with increasing energy during anisotropy episodes. A stronger pitch angle scattering at higher velocities is argued as a potential cause for this energy dependence. A possible cause for this velocity dependence arising from weak rigidity dependence of the scattering mean free path and resulting velocity-dominated scattering rate is discussed. This interpretation is consistent with a recently reported lack of corresponding GCR electron anisotropies.

Keywords: Heliopause, Heliosphere, Cosmic ray detectors, Galactic cosmic rays, Interstellar magnetic fields, Interstellar medium
The Variability Behavior of NGC 925 ULX-3. We report the results of a 2019-2021 monitoring campaign with Swift and associated target-of-opportunity observations with XMM-Newton and NuSTAR, examining the spectral and timing behavior of the highly variable ultraluminous X-ray source (ULX) NGC 925 ULX-3. We find that the source exhibits a 127-128-day periodicity, with fluxes typically ranging from 1 × 10-13 to 8 × 10-13 erg s-1 cm-2. We do not find strong evidence for a change in period over the time that NGC 925 ULX-3 has been observed, although the source may have been in a much lower flux state when first observed with Chandra in 2005. We do not detect pulsations, and we place an upper limit on the pulsed fraction of ~40% in the XMM-Newton band, consistent with some previous pulsation detections at low energies in other ULXs. The source exhibits a typical ULX spectrum that turns over in the NuSTAR band and can be fitted using two thermal components. These components have a high temperature ratio that may indicate the lack of extreme inner disk truncation by a magnetar-level magnetic field. We examine the implications for a number of different models for superorbital periods in ULXs, finding that a neutron star with a magnetic field of ~1012 G may be plausible for this source. The future detection of pulsations from this source would allow for the further testing and constraining of such models.

Keywords: Neutron stars, Ultraluminous x-ray sources, Accretion, X-ray sources
Spatial Distribution of Dark Matter in and Around Galaxy Clusters Traced by Galaxies, Gas, and Intracluster Stars in a Simulated Universe. To understand how well galaxies, gas, and intracluster stars trace dark matter in and around galaxy clusters, we use the IllustrisTNG cosmological hydrodynamical simulation and compare the spatial distribution of dark matter with that of baryonic components in clusters. To quantify the global morphology of the density distribution of each component in clusters, we fit an ellipse to the density contour of each component and derive shape parameters at different radii. We find that the ellipticity of dark matter is better correlated with that of galaxy mass-weighted number density, rather than with that of galaxy number density or galaxy velocity dispersion. We thus use the galaxy mass-weighted number density map as representative of the galaxy maps. Among three different density maps from galaxies, gas, and intracluster stars, the ellipticity of dark matter is best reproduced by that of the galaxy map over the entire radii. The virialized galaxy clusters show a better correlation of spatial distribution between dark matter and other components than the unvirialized clusters, suggesting that it requires some time for each component to follow the spatial distribution of dark matter after merging events. Our results demonstrate that galaxies are still good tracers of dark matter distribution even in the nonlinear regime corresponding to the scales in and around galaxy clusters, being consistent with the case where galaxies trace well the matter distribution on cosmologically large scales.

Keywords: Galaxy clusters, Hydrodynamical simulations, Dark matter distribution, Intracluster medium
Extreme Eccentricities of Triple Systems: Analytic Results. Triple stars and compact objects are ubiquitously observed in nature. Their long-term evolution is complex; in particular, the von Zeipel-Lidov-Kozai (ZLK) mechanism can potentially lead to highly eccentric encounters of the inner binary. Such encounters can lead to a plethora of interacting binary phenomena, as well as stellar and compact-object mergers. Here we find implicit analytical formulae for the maximal eccentricity, ${e}_{\max }$ , of the inner binary undergoing ZLK oscillations, where both the test-particle limit (parameterized by the inner-to-outer angular momentum ratio η) and the double-averaging approximation (parameterized by the period ratio, ϵ SA) are relaxed, for circular outer orbits. We recover known results in both limiting cases (either η or ϵ SA → 0) and verify the validity of our model using numerical simulations. We test our results with two accurate numerical N-body codes, REBOUND for Newtonian dynamics and TSUNAMI for general-relativistic dynamics, and find excellent correspondence. We discuss the implications of our results for stellar triples and both stellar and supermassive triple black hole mergers.

Keywords: Supermassive black holes, Multiple stars, Close binary stars, Stellar mass black holes, Stellar dynamics, Galaxy mergers, Compact objects
Magnetic Field of Molecular Gas Measured with the Velocity Gradient Technique I. Orion A. Magnetic fields play an important role in the evolution of molecular clouds and star formation. Using the velocity gradient technique (VGT) model, we measured the magnetic field in Orion A using the 12CO, 13CO, and C18O(1-0) emission lines at a scale of ~0.07 pc. The measured B field shows an east-west orientation that is perpendicular to the integral shaped filament of Orion A at large scale. The VGT magnetic fields obtained from 13CO and C18O are in agreement with the B field that is measured from the Planck 353 GHz dust polarization at a scale of ~0.55 pc. Removal of density effects by using a velocity decomposition algorithm can significantly improve the accuracy of the VGT in tracing magnetic fields with the 12CO(1-0) line. The magnetic field strengths of seven subclouds, OMC-1, OMC-2, OMC-3, OMC-4, OMC-5, L 1641-N, and NGC 1999, have also been estimated with the Davis-Chandrasekhar-Fermi and the Two Mach Numbers technique, and these are found to be in agreement with previous results obtained from dust polarization at far-infrared and submillimeter wavelengths. At smaller scales, the VGT prove a good method to measure magnetic fields.

Keywords: Interstellar magnetic fields, Interstellar dynamics, Interstellar medium
Implications of NICER for Neutron Star Matter: The QHC21 Equation of State. The recent NICER measurement of the radius of the neutron star PSR J0740+6620, and the inferred small variation of radii from 1.4 to 2.1 M ⊙, reveal key features of the equation of state of neutron star matter. The pressure rises rapidly in the regime of baryon density n ~ 2-4 times nuclear saturation density, n 0-the region where we expect hadronic matter to be undergoing transformation into quark matter-and the pressure in the nuclear regime is greater than predicted by microscopic many-body variational calculations of nuclear matter. To incorporate these insights into the microscopic physics from the nuclear to the quark matter regimes, we construct an equation of state, QHC21, within the framework of quark-hadron crossover. We include nuclear matter results primarily based on the state-of-the-art chiral effective field theory, but also note results of using nuclear matter variational calculations based on empirical nuclear forces. We employ explicit nuclear degrees of freedom only up to n ~ 1.5 n 0, in order to explore the possibility of further physical degrees of freedom than nucleonic here. The resulting QHC21, which has a peak in sound velocity in ~2-4 n 0, is stiffer than the earlier QHC19 below 2 n 0, predicting larger radii in substantial agreement with the NICER data.

Keywords: Neutron star cores
Evolution of Accretion Modes between Spectral States Inferred from Spectral and Timing Analysis of Cygnus X-1 with Insight-HXMT Observations. We execute a detailed spectral-timing study of Cygnus X-1 in the low/hard, intermediate, and high/soft states with observations from the Hard X-ray Modulation Telescope. The broadband energy spectra fit well with the "truncated disk model": the inner boundary of the accretion disk stays within ~10 R g and moves inward as the source softens. Through studying the power density spectrum, rms, and Fourier frequency component resolved spectroscopy, we find that the X-ray variations are generated in two different regions for each state. We discover that the major contribution to the X-ray variation is from the hot corona rather than the accretion disk. We suggest a scenario with different coronal geometry for each state based on the truncated disk geometry in which the corona envelops the disk to form a sandwich geometry in the low/hard state, and then gradually moves away from the disk in a direction perpendicular to the disk until it forms a jet-like geometry in the high/soft state.

Keywords: High mass x-ray binary stars
The Effect of Accretion Rate and Composition on the Structure of Ice-rich Super-Earths. It is reasonable to assume that the structure of a planet and the interior distribution of its components are determined by its formation history. We thus follow the growth of a planet from a small embryo through its subsequent evolution. We estimate the accretion rate range based on a protoplanetary disk model at a large-enough distance from the central star for water ice to be a major component. We assume the accreted material to be a mixture of silicate rock and ice, with no H-He envelope, as the accretion timescale is much longer than the time required for the nebular gas to dissipate. We adopt a thermal evolution model that includes accretional heating, radioactive energy release, and separation of ice and rock. Taking the Safronov parameter and the ice-to-rock ratio as free parameters, we compute growth and evolutionary sequences for different parameter combinations, for 4.6 Gyr. We find the final structure to depend significantly on both parameters. Low initial ice-to-rock ratios and high accretion rates, each resulting in an increased heating rate, lead to the formation of extended rocky cores, while the opposite conditions leave the composition almost unchanged and result in relatively low internal temperatures. When rocky cores form, the ice-rich outer mantles still contain rock mixed with the ice. We find that a considerable fraction of the ice evaporates upon accretion, depending on parameters, and assume it is lost, thus the final surface composition and bulk density of the planet do not necessarily reflect the protoplanetary disk composition.

Keywords: Extrasolar rocky planets, Super Earths, Exoplanet evolution, Surface ices, Exoplanet structure, Exoplanet formation, Planet formation
A Candle in the Wind: A Radio Filament in the Core of the A3562 Galaxy Cluster. Using a MeerKAT observation of the galaxy cluster A3562 (a member of the Shapley supercluster), we have discovered a narrow, long and straight, very faint radio filament, which branches out at a straight angle from the tail of a radio galaxy located in projection near the core of the cluster. The radio filament spans 200 kpc and aligns with a sloshing cold front seen in the X-rays, staying inside the front in projection. The radio spectral index along the filament appears uniform (within large uncertainties) at α ≃ -1.5. We propose that the radio galaxy is located outside the cold front but dips its tail under the front. The tangential wind that blows there may stretch the radio plasma from the radio galaxy into a filamentary structure. Some reacceleration is needed in this scenario to keep the radio spectrum uniform. Alternatively, the cosmic-ray electrons from that spot in the tail can spread along the cluster magnetic field lines, straightened by that same tangential flow, via anomalously fast diffusion. Our radio filament can provide constraints on this process. We also uncover a compact radio source at the brightest cluster galaxy that is 2-3 orders of magnitude less luminous than those in typical cluster central galaxies-probably an example of a brightest cluster galaxy starved of accretion fuel by gas sloshing.

Keywords: Galaxy clusters, Extragalactic radio sources, Radio galaxies, Tailed radio galaxies, Radio continuum emission, Intracluster medium
Validation and Interpretation of a Three-dimensional Configuration of a Magnetic Cloud Flux Rope. One strong magnetic cloud (MC) with a magnetic field magnitude reaching ~40 nT at 1 au during 2012 June 16-17 is examined in association with a preexisting magnetic flux rope (MFR) identified on the Sun. The MC is characterized by a quasi-three-dimensional (3D) flux rope model based on in situ measurements from the Wind spacecraft. The contents of the magnetic flux and other parameters are quantified. In addition, a correlative study with the corresponding measurements of the same structure crossed by the Venus Express (VEX) spacecraft at a heliocentric distance of 0.7 au and with an angular separation of ~6° in longitude is performed to validate the MC modeling results. The spatial variation between the Wind and VEX magnetic field measurements is attributed to the 3D configuration of the structure appearing as a knotted bundle of flux. A comparison of the magnetic flux contents between the MC and the preexisting MFR on the Sun indicates that the 3D reconnection process accompanying an M1.9 flare may correspond to the magnetic reconnection between the field lines of the preexisting MFR rooted in the opposite polarity footpoints. Such a process reduces the amount of the axial magnetic flux in the erupted flux rope, by approximately 50%, in this case.

Keywords: Magnetohydrodynamics, Solar coronal mass ejections, Magnetic fields, Solar corona
Dust Grain Growth and Dusty Supernovae in Low-metallicity Molecular Clouds. We present 3D hydrodynamical models of the evolution of superbubbles powered by stellar winds and supernovae from young coeval massive star clusters within low-metallicity (Z = 0.02 Z ⊙), clumpy molecular clouds. We explore the initial stages of the superbubble evolution, including the occurrence of pair-instability and core-collapse supernovae. Our aim is to study the occurrence of dust grain growth within orbiting dusty clumps, and in the superbubble's swept-up supershell. We also aim to address the survival of dust grains produced by sequential supernovae. The model accounts for the star cluster gravitational potential and self-gravity of the parent cloud. It also considers radiative cooling (including that induced by dust) and a state-of-the-art population synthesis model for the coeval cluster. As shown before, a superbubble embedded into a clumpy medium becomes highly distorted, expanding mostly due to the hot gas streaming through low-density channels. Our results indicate that in the case of massive (~107 M ⊙) molecular clouds, hosting a super star cluster (~5.6 × 105 M ⊙), grain growth increments the dust mass at a rate ~4.8 × 10-5 M ⊙ yr-1 during the first 2.5 Myr of the superbubble's evolution, while the net contribution of pair-instability and core-collapse supernovae to the superbubble's dust budget is ~1200 M ⊙ (M SC/5.6 × 105 M ⊙), where M SC is the stellar mass of the starburst. Therefore, dust grain growth and dust injection by supernovae lead to the creation of, without invoking a top-heavy initial mass function, massive amounts of dust within low-metallicity star-forming molecular clouds, in accordance with the large dust mass present in galaxies soon after the onset of cosmic reionization.

Keywords: Interstellar dust, Hydrodynamical simulations, Young massive clusters, Molecular clouds, Supernovae