Sazuna/UAT_keywords huggingface dataset:
Testing Earthlike Atmospheric Evolution on Exo-Earths through Oxygen Absorption: Required Sample Sizes and the Advantage of Age-based Target Selection. Life has had a dramatic impact on the composition of Earth's atmosphere over time, which suggests that statistical studies of other inhabited planets' atmospheres could reveal how they coevolve with life. While many evolutionary pathways are possible for inhabited worlds, a possible starting hypothesis is that most of them evolve similarly to Earth, which we propose could lead to a positive "age-oxygen correlation" between the ages of inhabited planets and the fraction which have oxygen-rich atmospheres. We demonstrate that next-generation space observatories currently under consideration could test this hypothesis, but only if the stellar age distribution of the target sample is carefully considered. We explore three possible parameterizations of the age-oxygen correlation, finding that they yield similar results. Finally, we examine how abiotic oxygen sources could affect the results, and discuss how measuring the age dependence of oxygen could shed light on whether it is a reliable biosignature. Future efforts can expand upon this groundwork by incorporating detailed models of the redox balance of terrestrial planets and its dependence on stellar and planetary properties.

Keywords: Exoplanet evolution, Biosignatures, Astrobiology, Habitable planets
Tidal Interaction between the UX Tauri A/C Disk System Revealed by ALMA. We present sensitive and high angular-resolution (∼0"2-0"3) (sub)millimeter (230 and 345 GHz) continuum and CO(2-1)/CO(3-2) line archive observations of the disk star system in UX Tauri carried out with the Atacama Large Millimeter/Submillimeter Array. These observations reveal the gas and dusty disk surrounding the young star UX Tauri A with a large signal-to-noise ratio (&gt;400 in the continuum and &gt;50 in the line), and for the first time we detect the molecular gas emission associated with the disk of UX Tauri C (with a size for the disk of &lt;56 au). No (sub)millimeter continuum emission is detected at the 5σ level (0.2 mJy at 0.85 mm) associated with UX Tauri C. For the component UX Tauri C, we estimate a dust disk mass of ≤0.05 M⊕. Additionally, we report a strong tidal disk interaction between both disks, UX Tauri A/C, separated 360 au in projected distance. The CO line observations reveal marked spiral arms in the disk of UX Tauri A and an extended redshifted stream of gas associated with the UX Tauri C disk. No spiral arms are observed in the dust continuum emission of UX Tauri A. Assuming a Keplerian rotation we estimate the enclosed masses (disk+star) from their radial velocities in 1.4 ± 0.6 M⊙ for UX Tauri A, and 70 ± 30/sin I Jupiter masses for UX Tauri C (the latter coincides with the mass upper limit value for a brown dwarf). The observational evidence presented here lead us to propose that UX Tauri C has a close approach of a possible wide, evolving, and eccentric orbit around the disk of UX Tauri A, causing the formation of spiral arms and a stream of molecular gas falling toward UX Tauri C.

Keywords: Interstellar molecules, Circumstellar gas, Radio interferometers
Interplanetary Coronal Mass Ejection Associated Forbush Decreases in Neutron Monitors. Interplanetary coronal mass ejections (ICMEs) are eruptions of plasma that propagate outward through the heliosphere. ICMEs, and the shocks they drive, cause a sudden decrease in the cosmic-ray flux in their local area of the heliosphere, called a Forbush decrease (FD). A method of defining FDs is established, and an automated process for identifying FDs in neutron monitor (NM) data is created. The correlation between ICME properties and FD magnitude in 12 different NMs is examined for 91 ICME-associated FD events occurring from 2001 through 2019 August. A number of ICME properties show positive correlation with FD magnitude, with decreasing correlation strength as NM cutoff rigidity increases.

Keywords: Heliosphere, Galactic cosmic rays, Solar coronal mass ejection shocks, Solar activity, Solar-terrestrial interactions
Systematic Search for γ-Ray Periodicity in Active Galactic Nuclei Detected by the Fermi Large Area Telescope. We use nine years of γ-ray data provided by the Fermi Large Area Telescope (LAT) to systematically study the light curves (LCs) of more than 2000 active galactic nuclei (AGN) included in recent Fermi-LAT catalogs. Ten different techniques are used, which are organized in an automatic periodicity-search pipeline, in order to search for evidence of periodic emission in γ rays. Understanding the processes behind this puzzling phenomenon will provide a better view about the astrophysical nature of these extragalactic sources. However, the observation of temporal patterns in γ-ray LCs of AGN is still challenging. Despite the fact that there have been efforts to characterize the temporal emission of some individual sources, a systematic search for periodicities by means of a full likelihood analysis applied to large samples of sources was missing. Our analysis finds 11 AGN, of which 9 are identified for the first time, showing periodicity at more than 4σ in at least four algorithms. These findings will help in solving questions related to the astrophysical origin of this periodic behavior.

Keywords: Period search , Active galactic nuclei, Time series analysis, Gamma-ray telescopes
The Preservation of Super-Earths and the Emergence of Gas Giants after Their Progenitor Cores Have Entered the Pebble-isolation Phase. The omnipresence of super-Earths suggests that they are able to be retained in natal disks around low-mass stars, whereas exoplanets' mass distributions indicate that some cores have transformed into gas giants through runaway gas accretion at ≳1 au from solar-type stars. In this paper, we show that transition to runaway gas accretion by cores may be self-impeded by an increase of the grain opacity in their envelope after they have acquired sufficient mass (typically ∼ 10M⊕) to enter a pebble-isolation phase. The accumulation of approximately millimeter- to meter-sized pebbles in their migration barriers enhances their local fragmentation rates. The freshly produced submillimeter grains pass through the barrier, elevate the effective dust opacity, and reduce the radiative flux in the core's envelope. These effects alone are adequate to suppress the transition to runaway accretion and preserve super-Earths in the stellar proximity (∼0.1 au), albeit entropy advection between the envelope and the disk can further reduce the accretion rate. At an intermediate distance (∼1 au) from their host stars, the escalation in the dust opacity dominates over entropy advection in stalling the transition to runaway accretion for marginally pebble-isolated cores. Beyond a few astronomical unit, the transformation of more-massive cores to gas giants is reachable before severe depletion of disk gas. This requirement can be satisfied either in extended disks with large scale height via orderly accretion of migrating pebbles or through the mergers of oligarchic protoplanetary embryos, and can account for the correlated occurrence of long-period gas giants and close-in super-Earths.

Keywords: Accretion, Super Earths, Protoplanetary disks, Planet formation
Modeling Photoionized Turbulent Material in the Circumgalactic Medium. II. Effect of Turbulence within a Stratified Medium. The circumgalactic medium (CGM) of nearby star-forming galaxies shows clear indications of O VI absorption accompanied by little to no detectable N V absorption. This unusual spectral signature, accompanied by highly nonuniform absorption from lower-ionization-state species, indicates that the CGM must be viewed as a dynamic, multiphase medium, such as occurs in the presence of turbulence. Motivated by previous isotropic turbulent simulations, we carry out chemodynamical simulations of stratified media in a Navarro-Frenk-White (NFW) gravitational potential with a total mass of 1012 M⊙ and turbulence that decreases radially. The simulations assume a metallicity of 0.3 Z⊙ and a redshift-zero metagalatic UV background, and they track ionizations, recombinations, and species-by-species radiative cooling using the MAIHEM package. We compare a suite of ionic column densities with the COS-Halos sample of low-redshift star-forming galaxies. Turbulence with an average one-dimensional velocity dispersion of ≈40 km s-1, corresponding to an energy injection rate of ≈4 × 1049 erg yr-1, produces a CGM that matches many of the observed ionic column densities and ratios. In this simulation, the NN V/NO VI ratio is suppressed from its equilibrium value due to a combination of radiative cooling and cooling from turbulent mixing. This level of turbulence is consistent with expectations from observations of better constrained, higher-mass systems and could be sustained by energy input from supernovae, gas inflows, and dynamical friction from dark matter subhalos. We also conduct a higher resolution ≈40 km s-1 run, which yields smaller-scale structures but remains in agreement with observations.

Keywords: Astrochemistry, Circumgalactic medium
The Hills Mechanism and the Galactic Center S-stars. Our Galactic center contains young stars, including the few million year-old clockwise disk between 0.05 and 0.5 pc from the Galactic center and the S-star cluster of B-type stars at a galactocentric distance of 0.01 pc. Recent observations suggest the S-stars are remnants of tidally disrupted binaries from the clockwise disk. In particular, Koposov et al. discovered a hypervelocity star that was ejected from the Galactic center 5 Myr ago with a velocity vector consistent with the disk. We perform a detailed study of this binary disruption scenario. First, we quantify the plausible range of binary semimajor axes in the disk. Dynamical evaporation of such binaries is dominated by other disk stars rather than by the isotropic stellar population. For the expected range of semimajor axes in the disk, binary tidal disruptions can reproduce the observed S-star semimajor axis distribution. Reproducing the observed thermal eccentricity distribution of the S-stars requires an additional relaxation process. The flight time of the Koposov star suggests that this process must be effective within 10 Myr. We consider three possibilities: (I) scalar resonant relaxation from the observed isotropic star cluster, (II) torques from the clockwise disk, and (III) an intermediate-mass black hole. We conclude that the first and third mechanisms are fast enough to reproduce the observed S-star eccentricity distribution. Finally, we show that the primary star from an unequal-mass binary would be deposited at larger semimajor axes than the secondary, possibly explaining the dearth of O stars among the S-stars.

Keywords: Galactic center, Binary stars, Hypervelocity stars
Cosmic Evolution of Stellar-mass Black Hole Merger Rate in Active Galactic Nuclei. Binary black hole mergers encode information about their environment and the astrophysical processes that led to their formation. Measuring the redshift dependence of their merger rate will help probe the formation and evolution of galaxies and the evolution of the star formation rate. Here we compute the cosmic evolution of the merger rate for stellar-mass binaries in the disks of active galactic nuclei (AGNs). We focus on recent evolution out to redshift z = 2, covering the accessible range of current Earth-based gravitational-wave observatories. On this scale, the AGN population density is the main contributor to redshift dependence. We find that the AGN-assisted merger rate varies by less than a factor of two in the range 0 &lt; z ≤ 2, comparable to the expected level of evolution for globular clusters, but much smaller than the order-of-magnitude evolution for field binaries.

Keywords: Gravitational wave astronomy, Active galactic nuclei
Photospheric Polarization Signatures from Long Gamma-Ray Burst Simulations. A comprehensive understanding of gamma-ray bursts (GRBs) has been elusive due to the variety of questions surrounding the radiation mechanism at play in these events. Polarization measurements of GRBs can heavily constrain the relevant radiation mechanisms and the structure of the GRB jet; however, there is a limited number of theoretical predictions that observed GRB polarizations can be compared against. Here, we conduct radiative transfer calculations of a set of two-dimensional relativistic hydrodynamic long GRB (LGRB) jet simulations, of a constant and a variable jet, using the Monte Carlo Radiation Transport (MCRaT) code. MCRaT has been enhanced by the inclusion of polarization; it has been first verified by reproducing a variety of results in the literature and then used to obtain the time-integrated and time-resolved polarization degrees and angles of the synthetic LGRBs. While the obtained time-integrated polarization degrees (≲1%) are consistent with the constraints from the POLAR experiment, they are lower than other theoretical studies due to the lack of strong gradients in the model jet profiles that we use. The time-resolved results suggests that GRBs with wide jets observed on axis will have small polarization degrees (≲2%) and constant polarization angles, during the brightest portion of the light curve. GRBs observed off-axis will have larger polarization degrees and polarization angles that change with the temporal structure of radiating shells in the outflow. We then place our results in the context of GRB prompt emission models and future LEAP and POLAR-2 GRB polarimetry detections.

Keywords: Radiative transfer simulations, Gamma-ray bursts, Hydrodynamics
Results of 12 yr of Pulsar Timing at Nanshan. I.. We have used the Nanshan 25 m Radio Telescope at Xinjiang Astronomical Observatory to obtain timing observations of 87 pulsars from 2002 July to 2014 March. Using the "Cholesky" timing analysis method we have determined positions and proper motions for 48 pulsars, 24 of which are improved positions compared to previously published values. We also present the first published proper motions for nine pulsars and improved proper motions for 21 pulsars using the pulsar timing and position-comparison method. The pulsar rotation parameters are derived and are more accurate than previously published values for 36 pulsars. Glitches are detected in three pulsars: PSRs J1722-3632, J1852-0635, and J1957+2831. For the first two, the glitches are large, with Δνg/ν &gt; 10-6, and they are the first detected glitches in these pulsars. PSR J1722-3632 is the second oldest pulsar, with a large glitch. For the middle-age pulsars (τc &gt; 105 yr), the calculated braking indices, $| n| $ , are strongly correlated with τc and the numbers of positive and negative values of n are almost equal. For young pulsars (τc &lt; 105 yr), there is no correlation between $| n| $ and τc and most have n &gt; 0.

Keywords: Neutron stars, Pulsar timing method, Pulsars, Radio pulsars
Physics of Magnetohydrodynamic Rossby Waves in the Sun. Evidence of the existence of hydrodynamic and MHD Rossby waves in the Sun is accumulating rapidly. We employ an MHD Rossby wave model for the Sun in simplified Cartesian geometry, with a uniform toroidal field and no differential rotation, to analyze the role of each force that contributes to Rossby wave dynamics, and compute fluid particle trajectories followed in these waves. This analysis goes well beyond the traditional formulation of Rossby waves in terms of conservation of vorticity. Hydrodynamic Rossby waves propagate retrograde relative to the rotation of the reference frame, while MHD Rossby waves can be both prograde and retrograde. Fluid particle trajectories are either clockwise or counterclockwise spirals, depending on where in the wave pattern they are initiated, that track generally in the direction of wave propagation. Retrograde propagating MHD Rossby waves move faster than their hydrodynamic counterparts of the same wavelength, becoming Alfvén waves at very high field strengths. Prograde MHD Rossby waves, which have no hydrodynamic counterpart, move more slowly eastward than retrograde MHD Rossby waves for the same toroidal field, but with a speed that increases with toroidal field, in the high field limit again becoming Alfvén waves. The longitude and latitude structures of all these waves, as seen in their velocity streamlines and perturbation field lines as well as fluid particle trajectories, are remarkably similar for different toroidal fields, rotation, longitudinal wavelength, and direction of propagation.

Keywords: Magnetohydrodynamics, Solar rotation, The Sun, Solar magnetic fields, Solar activity
Blast Waves from Magnetar Flares and Fast Radio Bursts. Magnetars younger than one century are expected to be hyperactive: besides winds powered by rotation, they can generate frequent magnetic flares, which launch powerful blast waves into the wind. The resulting magnetized shocks act as masers producing bright radio emission. This theoretical picture predicts radio bursts with the following properties. (1) GHz radio emission occurs at radii $r\sim {10}^{14}\,\mathrm{cm}$ and lasts $\lesssim 1$ ms in the observer's time. (2) Induced scattering in the surrounding wind does not suppress the radio burst. (3) The emission has linear polarization set by the magnetar rotation axis. (4) The emission drifts to lower frequencies during the burst, and its duration broadens at lower frequencies. (5) Blast waves in inhomogeneous winds may emit variable radio bursts; periodicity might appear on submillisecond timescales if the magnetar rotates with a ∼1 s period. However, the observed burst structure is likely changed by lensing effects during propagation through the host galaxy. (6) The magnetar bursts should repeat, with rare ultrastrong events (possibly up to ∼1043 erg in radio waves) or more frequent weak bursts. (7) When a repeating magnetic flare strikes the wind bubble in the tail of a previous flare, the radio burst turns into a bright optical burst lasting $\lesssim 1\,{\rm{s}}$ . Locations of hyperactive magnetars in their host galaxies depend on how they form: magnetars created in supernova explosions will trace star formation regions, and magnetars formed in mergers of compact objects will be offset. The merger magnetars are expected to be particularly hyperactive.

Keywords: Neutron stars, Optical bursts, Shocks, Plasma astrophysics, Radio bursts, Magnetars
Figuring Out Gas &amp; Galaxies in Enzo (FOGGIE). III. The Mocky Way: Investigating Biases in Observing the Milky Way's Circumgalactic Medium. The circumgalactic medium (CGM) of the Milky Way is mostly obscured by nearby gas in position-velocity space because we reside inside the Galaxy. Substantial biases exist in most studies of the Milky Way's CGM that focus on easier-to-detect high-velocity gas. With mock observations on a Milky Way analog from the Figuring Out Gas &amp; Galaxies in Enzo (FOGGIE) simulation, we investigate four observational biases related to the Milky Way's CGM. First, QSO absorption-line studies probe a limited amount of the CGM mass: only 35% of the mass is at high Galactic latitudes $| b| \gt 20^\circ $ , of which only half is moving at $| {V}_{\mathrm{LSR}}| \gtrsim 100\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . Second, the inflow rate ( $\dot{M}$ ) of the cold gas observable in H I 21 cm is reduced by a factor of ∼10 as we switch from the local standard of rest to the galaxy's rest frame; meanwhile, the $\dot{M}$ of the cool and warm gas does not change significantly. Third, O VI and N V are promising ions to probe the Milky Way's outer CGM ( $r\gtrsim 15$ kpc), but C IV may be less sensitive. Lastly, the scatter in ion column density is a factor of 2 higher if the CGM is observed from the inside out than from external views because of the gas radial density profile. Our work highlights that observations of the Milky Way's CGM, especially those using H I 21 cm and QSO absorption lines, are highly biased. We demonstrate that these biases can be quantified and calibrated through synthetic observations with simulated Milky Way analogs.

Keywords: Hydrodynamical simulations, Quasar absorption line spectroscopy, High-velocity clouds, Spectroscopy, Circumgalactic medium, Milky Way Galaxy
Rotational Disruption of Dust Grains by Mechanical Torques for High-velocity Gas-Grain Collisions. Dust grains moving at hypersonic velocities of ${V}_{d}\gtrsim 100\,\mathrm{km}\,{{\rm{s}}}^{-1}$ through an ambient gas are known to be destroyed by nonthermal sputtering. Yet, previous studies of nonthermal sputtering disregarded the fact that dust grains can be spun up to suprathermal rotation by stochastic mechanical torques from gas-grain collisions. In this paper, we show that such grain suprathermal rotation can disrupt a small grain into small fragments because induced centrifugal stress exceeds the maximum tensile strength of grain material, Smax. We term this mechanism MEchanical Torque Disruption (METD). We find that METD is more efficient than nonthermal sputtering in destroying the smallest grains (a &lt; 10 nm) of non-ideal structures, moving with velocities of ${V}_{d}\lt 500\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . The ratio of rotational disruption to sputtering time is ${\tau }_{\mathrm{disr}}$ / ${\tau }_{\mathrm{sp}}\sim 0.7({S}_{\max }$ / ${10}^{9}\,\mathrm{erg}\,{\mathrm{cm}}^{-3})({\bar{A}}_{\mathrm{sp}}$ / $12){({Y}_{\mathrm{sp}}/0.1)(a/0.01\mu {\rm{m}})}^{3}{(300\mathrm{km}{{\rm{s}}}^{-1}/{V}_{d})}^{2}$ , where a is the radius of spherical grains and Ysp is the sputtering yield. We also consider the high-energy regime and find that the rate of METD is reduced and becomes less efficient than sputtering for ${V}_{d}\gt 500\,\mathrm{km}\,{{\rm{s}}}^{-1}$ because impinging particles only transfer part of their momentum to the grain. We finally discuss the implications of the METD mechanism for the destruction of hypersonic grains accelerated by radiation pressure, as well as grains in fast shocks. Our results suggest that the destruction of small grains by METD in fast shocks of supernova remnants may be more efficient than previously predicted by nonthermal sputtering, depending on grain internal structures.

Keywords: Interstellar dust, Interstellar dynamics, Interstellar medium, Interstellar dust processes
Cosmological Parameter Estimation from the Two-dimensional Genus Topology: Measuring the Shape of the Matter Power Spectrum. We present measurements of the two-dimensional genus of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) catalogs to constrain cosmological parameters governing the shape of the matter power spectrum. The BOSS data are divided into 12 concentric shells over the redshift range 0.2 &lt; z &lt; 0.6, and we extract the genus from the projected two-dimensional galaxy density fields. We compare the genus amplitudes to their Gaussian expectation values, exploiting the fact that this quantity is relatively insensitive to nonlinear gravitational collapse. The genus amplitude provides a measure of the shape of the linear matter power spectrum and is principally sensitive to Ωch2 and scalar spectral index ns. A strong negative degeneracy between Ωch2 and ns is observed, as both can increase small-scale power by shifting the peak and tilting the power spectrum, respectively. We place a constraint on the particular combination ${n}_{{\rm{s}}}^{3/2}{{\rm{\Omega }}}_{{\rm{c}}}{h}^{2}$ —we find ${n}_{{\rm{s}}}^{3/2}{{\rm{\Omega }}}_{{\rm{c}}}{h}^{2}=0.1121\pm 0.0043$ after combining the LOWZ and CMASS data sets, assuming a flat ΛCDM cosmology. This result is practically insensitive to reasonable variations of the power spectrum amplitude and linear galaxy bias. Our results are consistent with the Planck best fit ${n}_{{\rm{s}}}^{3/2}{{\rm{\Omega }}}_{{\rm{c}}}{h}^{2}=0.1139\pm 0.0009$ .

Keywords: Cosmological parameters from large-scale structure, Observational cosmology, Large-scale structure of the universe