Sazuna/UAT_keywords huggingface dataset:
Accretion and Extinction Variations in the Low-mass Pre-main-sequence Binary System WX Cha. Light curves of young star systems show photometric variability due to different kinematic and physical processes. One of the main contributors to the photometric variability is the changing mass accretion rate, which regulates the interplay between the forming young star and the protoplanetary disk. We collected high-resolution spectroscopy in eight different epochs, as well as ground-based and space-borne multiepoch optical and infrared photometry of WX Cha, an M0 binary system, with an almost edge-on disk (i = 87°) in the Chamaeleon I star-forming region. Spectroscopic observations cover 72 days, the ground-based optical monitoring covers 42 days while space-borne TESS photometry extends for 56 days. The multiwavelength light curves exhibit quasi-periodic variability of 0.35-0.53 mag in the near-infrared, and of 1.3 mag in the g band. We studied the variability of selected emission lines that trace the accretion, computed the accretion luminosity and the mass accretion rate using empirical relations, and obtained values between L acc ~ 1.6 L ☉ - 3.2 L ☉ and ${\dot{M}}_{\mathrm{acc}}\sim 3.31\times {10}^{-7}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}-7.76\,\times {10}^{-7}$ M ☉ yr-1. Our results show that WX Cha is accreting at a rate larger than what is typical for T Tauri stars in the same star-forming region with the same stellar parameters. We theorize that this is due to the higher disk mass of WX Cha than what is usual for stars with similar stellar mass and to the binary nature of the system. Daily changes in the accretion luminosity and in the extinction can explain the photometric variability. * Based on observations collected at the European Southern Observatory under ESO programs 2103.C-5025, 0103.A-9008, and 0100.C-0708(A).

Keywords: Binary stars, Light curves, Classical T Tauri stars, Star formation, Stellar accretion, Spectroscopy, Photometry
Molecular and Atomic Clouds Associated with the Gamma-Ray Supernova Remnant Puppis A. We have carried out a study of the interstellar medium (ISM) toward the shell-like supernova remnant (SNR) Puppis A using NANTEN CO and ATCA H I data. We synthesized a comprehensive picture of the SNR radiation by combining the ISM data with the gamma-ray and X-ray distributions. The ISM, both atomic and molecular gas, is dense and highly clumpy, and is distributed all around the SNR, but mainly in the northeast. The CO distribution revealed an enhanced line intensity ratio of CO(J = 2-1)/(J = 1-0) transitions as well as CO line broadening, which indicate shock heating/acceleration. The results support the assertion that Puppis A is located at 1.4 kpc, in the Local Arm. The ISM interacting with the SNR has a large mass of ~104 M ☉, which is dominated by H I, showing good spatial correspondence with the Fermi-LAT gamma-ray image. This favors a hadronic origin of the gamma-rays, while an additional contribution from a leptonic component is not excluded. The distribution of the X-ray ionization timescales within the shell suggests that the shock front ionized various parts of the ISM at epochs ranging over a few to ten thousand years. We therefore suggest that the age of the SNR is around 104 yr as given by the largest ionization timescale. We estimate the total cosmic-ray energy W p to be 1047 erg, which is well placed in the cosmic-ray escaping phase of an age-W p plot including more than ten SNRs.

Keywords: Gamma-ray sources, Supernova remnants, Cosmic ray sources, X-ray sources, Interstellar medium
Tracking a Beam of Electrons from the Low Solar Corona into Interplanetary Space with the Low Frequency Array, Parker Solar Probe, and 1 au Spacecraft. Type III radio bursts are the result of plasma emission from mildly relativistic electron beams propagating from the low solar corona into the heliosphere where they can eventually be detected in situ if they align with the location of a heliospheric spacecraft. Here we observe a type III radio burst from 0.1 to 16 MHz using the Parker Solar Probe (PSP) FIELDS Radio Frequency Spectrometer (RFS) and from 20 to 80 MHz using the Low Frequency Array (LOFAR). This event was not associated with any detectable flare activity but was part of an ongoing type III and noise storm that occurred during PSP encounter 2. A deprojection of the LOFAR radio sources into 3D space shows that the type III radio burst sources were located on open magnetic field from 1.6 to 3 R ⊙ and originated from a near-equatorial active region around longitude E48°. Combining PSP/RFS observations with WIND/WAVES and Solar Terrestrial Relations Observatory (STEREO) WAVES, we reconstruct the type III radio source trajectory in the heliosphere interior to PSP's position, assuming ecliptic confinement. An energetic electron enhancement is subsequently detected in situ at the STEREO A spacecraft at compatible times, although the onset and duration suggests the individual burst contributes a subset of the enhancement. This work shows relatively small-scale flux emergence in the corona can cause the injection of electron beams from the low corona into the heliosphere, without needing a strong solar flare. The complementary nature of combined ground and space-based radio observations, especially in the era of PSP, is also clearly highlighted by this study.

Keywords: Solar coronal radio emission, Heliosphere, Solar energetic particles, Solar corona, Active solar corona
Spectral Analysis of Gravity Waves in the Martian Thermosphere during Low Solar Activity Based on MAVEN/NGIMS Observations. Gravity waves (GWs) are important for vertical coupling between the lower and upper atmosphere on Mars. Saturated GWs will promote the acceleration of mean flow and turbulence generation, causing diffuse transport of energy and momentum. We analyze the spectral characteristics of GWs in the thermosphere on Mars during the low solar activity of Martian Year (MY) 35, based on CO2 density measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS) on board Mars Atmosphere and Volatile EvolutioN (MAVEN). The results are compared with those of MY33 at the higher solar activity. The vertical wavenumber spectral density obtained in the Martian thermosphere is similar to the semi-empirically predicted saturation spectrum in the Earth's atmosphere, with a logarithmic spectral slope around -3. The average spectral density of GWs shows saturation between 160 and 200 km and decreases with increasing altitude. Compared to MY33, GW activity is larger and less attenuated in MY35 as it propagates upward, implying that waves experience more favorable propagation conditions during low solar activity. Also, the dependence of GW activity on local time during this period is found to be different from previous studies, with the strongest GWs in the spring of MY35 occurring within 6-12 hr on the dayside, suggesting that the amplitude of the GWs in the Martian thermosphere during low solar activity is less controlled by the background temperature and is subject to dissipative effects of other factors, such as molecular viscosity and thermal conduction.

Keywords: Solar activity, Internal waves, Mars, Thermosphere
Phase Mixing and the 1/f Spectrum in the Solar Wind. The origin and evolution of the 1/f power law observed in the energy spectrum of solar coronal and solar wind fluctuations at scales of around an hour is not entirely understood. Several existing theories aim at explaining it, involving both linear and nonlinear mechanisms. An often overlooked property of the solar corona and solar wind is their highly inhomogeneous nature. In this paper we investigate the linear evolution of pure Alfvén and surface Alfvén waves propagating through a plasma that is inhomogeneous across the magnetic field. The inhomogeneity is given by density, which we model to be 2D colored noise, with power spectral slopes ranging from -2 to -1. Alfvén waves propagate independently on individual magnetic field lines, and eventually get completely out of phase through the process of phase mixing, leading to unrealistic spectra. When the coupling between the inhomogeneous background and the propagating waves is fully accounted for, transverse waves such as surface Alfvén waves (also referred to as kink or Alfvénic) appear, showing collective wave behavior of neighboring magnetic field lines with different Alfvén speeds. We show that the linear cascade of surface Alfvén wave energy, induced by phase mixing and resonant absorption, leads to a perpendicular wave energy spectrum, which tends to the perpendicular power spectrum of the background density. Based on our model, we propose that a perpendicular density power spectrum of 1/f in the solar corona can induce, through linear processes, the 1/f spectrum of the fluctuations that is observed at the largest scales.

Keywords: Solar physics, Solar wind, Plasma astrophysics, Magnetohydrodynamics
Laboratory Study of the Cameron Bands and UV Doublet in the Middle Ultraviolet 180-300 nm by Electron Impact upon CO<SUB>2</SUB> with Application to Mars. We have observed electron impact fluorescence from CO2 to excite the Cameron bands (CBs), CO (a 3Π → X 1Σ+; 180-280 nm), the first-negative group (1NG) bands, CO+ (B 2Σ+ → X 2Σ+; 180-320 nm), the fourth-positive group (4PG) bands, CO (A 1Π → X 1Σ+; 111-280 nm), and the UV doublet, CO2 + ( $\tilde{B}{\ }^{2}{{\rm{\Sigma }}}_{u}^{+}\to \tilde{X}{\ }^{2}{{\rm{\Pi }}}_{g};$ 288.3 and 289.6 nm) in the ultraviolet (UV). This wavelength range matches the spectral region of past and present spacecraft equipped to observe UV dayglow and aurora emissions from the thermospheres (100-300 km) of Mars and Venus. Our large vacuum system apparatus is able to measure the emission cross sections of the strongest optically forbidden UV transitions found in planetary spectra. Based on our cross-sectional measurements, previous CB emission cross-sectional errors exceed a factor of 3. The UV doublet lifetime is perturbed through $\tilde{B}{\ }^{2}{{\rm{\Sigma }}}_{u}^{+}-\tilde{A}{\ }^{2}{{\rm{\Pi }}}_{u}$ spin-orbit coupling. Forward modeling codes of the Mars dayglow have not been accurate in the mid-UV due to systematic errors in these two emission cross sections. We furnish absolute emission cross sections for several band systems over electron energies 20-100 eV for CO2. We present a CB lifetime, which together with emission cross sections, furnish a set of fundamental physical constants for electron transport codes such as AURIC (Atmospheric Ultraviolet Radiance Integrated Code). AURIC and Trans-Mars are used in the analysis of UV spectra from the Martian dayglow and aurora.

Keywords: Collisional processes, Mars, Molecular spectroscopy, Experimental techniques, Carbon dioxide, Molecular physics, Radiative processes
On the Nature of Rotation in the Praesepe Cluster. Although a large number of Galactic open clusters (OCs) have been identified, the internal kinematic properties (e.g., rotation) of almost all the known OCs are still far from clear. With the high-precision astrometric data of Gaia EDR3, we have developed a methodology to unveil the rotational properties of the Praesepe cluster. Statistics of the three-dimensional residual motions of the member stars reveal the presence of Praesepe's rotation and determine its spatial rotation axis. The mean rotation velocity of the Praesepe cluster within its tidal radius is estimated to be 0.2 ± 0.05 km s-1, and the corresponding rotation axis is tilted in relation to the Galactic plane with an angle of 41° ± 12°. We also analyzed the rms rotational velocity of the member stars around the rotation axis, and found that the rotation of the member stars within the tidal radius of Praesepe probably follows Newton's classical theorems.

Keywords: Stellar kinematics, Open star clusters
The Hubble Space Telescope Survey of M31 Satellite Galaxies. I. RR Lyrae-based Distances and Refined 3D Geometric Structure. We measure homogeneous distances to M31 and 38 associated stellar systems (-16.8 ≤ M  V  ≤ -6.0), using time-series observations of RR Lyrae stars taken as part of the Hubble Space Telescope Treasury Survey of M31 Satellites. From &gt;700 orbits of new/archival Advanced Camera for Surveys imaging, we identify &gt;4700 RR Lyrae stars and determine their periods and mean magnitudes to a typical precision of 0.01 day and 0.04 mag. Based on period-Wesenheit-metallicity relationships consistent with the Gaia eDR3 distance scale, we uniformly measure heliocentric and M31-centric distances to a typical precision of ~20 kpc (3%) and ~10 kpc (8%), respectively. We revise the 3D structure of the M31 galactic ecosystem and: (i) confirm a highly anisotropic spatial distribution such that ~80% of M31's satellites reside on the near side of M31; this feature is not easily explained by observational effects; (ii) affirm the thin (rms 7-23 kpc) planar "arc" of satellites that comprises roughly half (15) of the galaxies within 300 kpc from M31; (iii) reassess the physical proximity of notable associations such as the NGC 147/185 pair and M33/AND XXII; and (iv) illustrate challenges in tip-of-the-red-giant branch distances for galaxies with M  V  &gt; - 9.5, which can be biased by up to 35%. We emphasize the importance of RR Lyrae for accurate distances to faint galaxies that should be discovered by upcoming facilities (e.g., Rubin Observatory). We provide updated luminosities and sizes for our sample. Our distances will serve as the basis for future investigation of the star formation and orbital histories of the entire known M31 satellite system.

Keywords: RR Lyrae variable stars, Dwarf galaxies, Andromeda Galaxy, Distance measure
Effects of Radiative Diffusion on Dynamical Corotation Torque in Three-dimensional Protoplanetary Disks. The dynamical corotation torque arising from the deformation of horseshoe orbits, along with the vortensity gradient in the background disk, is important for determining the orbital migration rate and direction of low-mass planets. Previous two-dimensional studies have predicted that the dynamical corotation torque is positive, decelerating inward planet migration. In contrast, recent three-dimensional studies have shown that buoyancy resonance makes the dynamical corotation torque negative, accelerating inward migration. In this paper, we study the dependence of the dynamical corotation torque on thermal transport, using three-dimensional simulations. We first show that our results are consistent with previous three-dimensional studies when the disk is fully adiabatic. In more realistic radiative disks, however, radiative diffusion suppresses buoyancy resonance significantly, especially in high-altitude regions, and yields a positive dynamical corotation torque. This alleviates the issue of rapid migration being caused by the negative dynamical corotation torque in adiabatic disks. Our results suggest that radiative diffusion, together with stellar irradiation and accretion heating, are needed to accurately describe the migration of low-mass planets.

Keywords: Planetary migration, Planetary-disk interactions, Protoplanetary disks, Radiative transfer
The Mouse That Squeaked: A Small Flare from Proxima Cen Observed in the Millimeter, Optical, and Soft X-Ray with Chandra and ALMA. We present millimeter, optical, and soft X-ray observations of a stellar flare with an energy squarely in the regime of typical X1 solar flares. The flare was observed from Proxima Cen on 2019 May 6 as part of a larger multi-wavelength flare monitoring campaign and was captured by Chandra, the Las Cumbres Observatory Global Telescope, the Iréné du Pont Telescope at Las Campanas Observatory, and the Atacama Large Millimeter Array. Millimeter emission appears to be a common occurrence in small stellar flares that had gone undetected until recently, making it difficult to interpret these events within the current multi-wavelength picture of the flaring process. The May 6 event is the smallest stellar millimeter flare detected to date. We compare the relationship between the soft X-ray and millimeter emission to that observed in solar flares. The X-ray and optical flare energies of 1030.3 ± 0.2 and 1028.9 ± 0.1 erg, respectively, the coronal temperature of T = 11.0 ± 2.1 MK, and the emission measure of 9.5 ± 2.2 × 1049 cm-3 are consistent with M-X class solar flares. We find the soft X-ray and millimeter emission during quiescence are consistent with the Güdel-Benz relation, but not during the flare. The millimeter luminosity is &gt;100× higher than that of an equivalent X1 solar flare and lasts only seconds instead of minutes as seen for solar flares.

Keywords: Stellar x-ray flares, Millimeter astronomy, Red dwarf flare stars, Solar white-light flares, Optical flares, Solar x-ray flares, Solar radio flares
Testing Strong Gravitational Lensing Effects of Supermassive Compact Objects with Regular Spacetimes. We compare and contrast gravitational lensing, in the strong field limit, by the photon sphere in spherically symmetric regular electrically charged (REC) black holes (0 &lt; b ≤ b  E ) and with those by corresponding REC no-horizon spacetimes (b &gt; b  E ). Here, b is an additional parameter due to the charge and the value b = b  E  ≈ 0.226 corresponds to an extremal black hole with degenerate horizons. Interestingly, the spacetime admits a photon sphere for 0 &lt; b ≤ b  P  ≈ 0.247 and an anti-photon sphere only for b  E  &lt; b ≤ b  P . With no-horizon spacetime, images by lensing from the inside of the photon sphere (u &lt; u ps) can also appear. Interestingly, for the case of u &lt; u ps the deflection angle α  D  increases with u. We analyze the lensing observables by modeling compact objects Sgr A*, M87*, NGC 4649, and NGC 1332 as black holes and no-horizon spacetimes. The angular position θ ∞ and photon sphere radius x ps decrease with increasing parameter b. Our findings suggest that the angular separations (s) and magnification (r) of relativistic images inside the photon sphere may be higher than those outside. Moreover, the time delay for Sgr A* and M87* can reach ~8.8809 and ~12,701.8 minutes, respectively, at b = 0.2, deviating from Schwarzschild black holes by ~2.615 and ~4677 minutes. These deviations are insignificant for Sgr A* because it is too small, but they are sufficient for astronomical observation of M87* and some other black holes. With EHT bounds on the θ sh of Sgr A* and M87* within the 1σ region, placing bounds on the parameter b, our analysis concludes that REC black holes agree with the EHT results in finite space, whereas the corresponding REC no-horizon spacetimes are completely ruled out.

Keywords: Strong gravitational lensing, Gravitational deflection, Photon sphere, Event horizons, Compact objects, Astrophysical black holes
Cosmic-Ray Convection-Diffusion Anisotropy. Under nonuniform convection, the distribution of diffusive particles can exhibit dipole and quadrupole anisotropy induced by the fluid inertial and shear force, respectively. These convection-related anisotropies, unlike the Compton-Getting effect, typically increase with the cosmic-ray (CR) energy, and are thus candidate contributors for the CR anisotropy. In consideration of the inertial effect, CR observational data can be used to set an upper limit on the average acceleration of the local interstellar medium in the equatorial plane to be on the order of 100 μm s-2. Using Oort constants, the quadrupole anisotropy above 200 TeV may be modeled with the shear effect arising from the Galactic differential rotation.

Keywords: Interstellar dynamics, High energy astrophysics, Cosmic ray astronomy, Intergalactic gas, Interstellar plasma, Galactic cosmic rays, Interstellar medium, Particle astrophysics, Cosmic rays
Probing the Extent of Vertical Mixing in Brown Dwarf Atmospheres with Disequilibrium Chemistry. Evidence of disequilibrium chemistry due to vertical mixing in the atmospheres of many T- and Y-dwarfs has been inferred due to enhanced mixing ratios of CO and reduced NH3. Atmospheric models of planets and brown dwarfs typically parameterize this vertical mixing phenomenon with the vertical eddy diffusion coefficient, K  zz . While K  zz  can perhaps be approximated in the convective regions in the atmosphere with mixing length theory, in radiative regions, the strength of vertical mixing is uncertain by many orders of magnitude. With a new grid of self-consistent 1D model atmospheres from T eff of 400-1000 K, computed with a new radiative-convective equilibrium python code PICASO 3.0, we aim to assess how molecular abundances and corresponding spectra can be used as a probe of depth-dependent K  zz . At a given surface gravity, we find nonmonotonic behavior in the CO abundance as a function of T eff, as chemical abundances are sometimes quenched in either of two potential atmospheric convective zones, or quenched in either of two possible radiative zones. The temperature structure and chemical quenching behavior also change with gravity. We compare our models with available near-infrared and M-band spectroscopy of several T- and Y-dwarfs and assess their atmospheric vertical mixing profiles. We also compare to color-magnitude diagrams and make predictions for James Webb Space Telescope spectra. This work yields new constraints, and points the way to significant future gains, in determining K  zz , a fundamental atmospheric parameter in substellar atmospheres, with significant implications for chemistry and cloud modeling.

Keywords: Atmospheric composition, Brown dwarfs, Y dwarfs, T dwarfs
Transitions and Origin of the Type-B Quasi-periodic Oscillations in the Black Hole X-Ray Binary MAXI J1348-630. The fast transitions between different types of quasi-periodic oscillations (QPOs) are generally observed in black hole transient sources (BHTs). We present a detailed study of the timing and spectral properties of the transitions of type-B QPOs in MAXI J1348-630, observed by Insight-HXMT. The fractional rms variability-energy relationship and energy spectra reveal that type-B QPOs probably originate from jet precession. Compared to a weak power-law dominated power spectrum, when type-B QPOs are present, the corresponding energy spectrum shows an increase in the Comptonization component and the need for the xillverCp component, and a slight increase in the height of the corona when using the relxilllp model. Therefore, we suggest that a coupled inner disk-jet region is responsible for the observed type-B QPO transitions. The timescale for the appearance/disappearance of type-B QPOs is either long or short (seconds), which may indicate instability of the disk-jet structure. For these phenomena, we hypothesize that the Bardeen-Petterson effect causes the disk-jet structure to align with the BH spin axis or that the disappearance of small-scale jets bound by the magnetic flux tubes leads to the disappearance of type-B QPOs. We observed three events regarding the B/C transitions, one of which occurred over a short time period from ~9.2 Hz (C) to ~4.8 Hz (B). The energy spectral analysis for the other two transitions shows that when type-C QPO is present, the Comptonization flux is higher, the spectrum is harder, and the inner radius of the disk changes insignificantly. We suggest that type-C QPOs probably originate from relatively stronger jets or the corona.

Keywords: Black hole physics, X-ray binary stars, Jets, High energy astrophysics