Sazuna/UAT_keywords huggingface dataset:
Constraints on the Physical Properties of GW190814 through Simulations Based on DECam Follow-up Observations by the Dark Energy Survey. On 2019 August 14, the LIGO and Virgo Collaborations detected gravitational waves from a black hole and a 2.6 solar mass compact object, possibly the first neutron star-black hole merger. In search of an optical counterpart, the Dark Energy Survey (DES) obtained deep imaging of the entire 90% confidence level localization area with Blanco/DECam 0, 1, 2, 3, 6, and 16 nights after the merger. Objects with varying brightness were detected by the DES Pipeline, and we systematically reduced the candidate counterparts through catalog matching, light-curve properties, host-galaxy photometric redshifts, Southern Astrophysical Research spectroscopic follow-up observations, and machine-learning-based photometric classification. All candidates were rejected as counterparts to the merger. To quantify the sensitivity of our search, we applied our selection criteria to full light-curve simulations of supernovae and kilonovae as they would appear in the DECam observations. Because the source class of the merger was uncertain, we utilized an agnostic, three-component kilonova model based on tidally disrupted neutron star (NS) ejecta properties to quantify our detection efficiency of a counterpart if the merger included an NS. We find that, if a kilonova occurred during this merger, configurations where the ejected matter is greater than 0.07 solar masses, has lanthanide abundance less than 10-8.56, and has a velocity between 0.18c and 0.21c are disfavored at the 2σ level. Furthermore, we estimate that our background reduction methods are capable of associating gravitational wave signals with a detected electromagnetic counterpart at the 4σ level in 95% of future follow-up observations.

Keywords: Optical observation, Light curve classification , Gravitational wave sources, Astronomical simulations
A Mechanistic Study on the Formation of Acetic Acid (CH<SUB>3</SUB>COOH) in Polar Interstellar Analog Ices Exploiting Photoionization Reflectron Time-of-flight Mass Spectrometry. Acetic acid (CH3COOH) is considered a key molecule in the formation of the simplest amino acid, glycine, and consequently peptides. It is ubiquitous in the interstellar medium and has been detected toward hot cores, in the coma of comets, and on the surface of the comet 67P/Churyumov-Gerasimenko by the Rosetta mission. Here we present the isomer-selective formation of acetic acid in polar ice mixtures of water/acetaldehyde upon exposure to ionizing radiation in the form of energetic electrons as a proxy for secondary electrons generated once Galactic cosmic rays pass through interstellar ices. Acetic acid is formed even at low irradiation doses of only 0.13 eV molecule-1 (deuterium oxide) and 0.29 eV molecule-1 (acetaldehyde), representing molecular cloud lifetimes of 1 × 106 yr. Isotopic substitutions reveal that the dominant formation pathway is the barrierless radical-radical recombination of acetyl (CH3CO) with hydroxyl-d1 radicals (OD), whereas oxygen insertion does not yield any detectable amounts of acetic acid. This hitherto unknown reaction pathway will influence the relative abundances of distinct C2H4O2 isomers in chemical models aiming to constrain the reaction conditions by comparing these abundances. In contrast to its formation in nonpolar model ices, the formation in this polar binary ice is isomer-selective and produces acetic acid only.

Keywords: Interstellar molecules, Laboratory astrophysics, Chemical abundances, Astrochemistry, Interdisciplinary astronomy
Axion Oscillations in Binary Systems: Angle-action Surgery. Scalar, tensor waves induce oscillatory perturbations in Keplerian systems that can be probed with measurements of pulsar timing residuals. In this paper, we consider the imprint of coherent oscillations produced by ultralight axion dark matter on the Roemer time delay. We use the angle-action formalism to calculate the time evolution of the observed signal and its dependence on the orbital parameters and the axion phase. We derive exact analytical expressions for arbitrary binary pulsar mass ratio and eccentricity, alleviating the need for long numerical integrations. We emphasize the similarity of the expected signal-to-noise ratio with the response of a harmonic oscillator to an external oscillatory driving. We validate our theoretical predictions with numerical simulations. Our results furnish a useful benchmark for numerical codes and analysis procedures and, hopefully, will motivate the search for such imprints in real data.

Keywords: Milky Way dark matter halo, Dark matter, Celestial mechanics, Perturbation methods, Binary pulsars
Ultraviolet Line Identifications and Spectral Formation Near Max Light in Type Ia Supernova 2011fe. We present ultraviolet line identifications of near maximum-light Hubble Space Telescope observations of SN 2011fe using synthetic spectra generated from both SYNOW and PHOENIX. We find the spectrum to be dominated by blends of iron group elements Fe, Co, and Ni (as expected due to heavy line blanketing by these elements in the UV) and for the first time identify lines from C IV and Si IV in a supernova spectrum. We also find that classical delayed detonation models of SNe Ia are able to accurately reproduce the flux levels of SN 2011fe in the UV. Further analysis reveals that photionization edges play an important role in feature formation in the far-UV, and that temperature variations in the outer layers of the ejecta significantly alter the Fe III/Fe II ratio producing large flux changes in the far-UV and velocity shifts in mid-UV features. SN 2011fe is the best observed core-normal SNe Ia; therefore analysis of its UV spectra shows the power of UV spectra in discriminating between different metallicities and progenitor scenarios of SNe Ia, due to the fact that the UV probes the outermost layers of the SN Ia, which are most sensitive to metallicity and progenitor variations.

Keywords: Type Ia supernovae, Supernovae
How Do Galaxy Properties Affect Void Statistics?. Using mapping from dark matter halos to galaxy properties based on hydrodynamical simulations, we explore the impact of galaxy properties on the void size function and the void-galaxy correlation function. We replicate the properties of galaxies from Illustris on MassiveNus halos, to perform both luminosity and star formation rate cuts on MassiveNus halos. We compare the impact of such cuts on void properties with respect to cuts on halo mass (as usually performed on halo catalogs driven from N-body simulations). We find that void catalogs built from luminosity-selected galaxies and halos are consistent within errors, while void catalogs built from star formation rate-selected galaxies differ from void catalogs built on halos. We investigate the reason for this difference. Our work suggests that voids built on galaxy catalogs (selected through luminosity cuts) can be reliably studied using halos in dark matter simulations.

Keywords: Cosmology, Hydrodynamical simulations, Large-scale structure of the universe, Surveys, Voids, N-body simulations, Catalogs
Cosmological Constraints on Ω<SUB>m</SUB> and σ<SUB>8</SUB> from Cluster Abundances Using the GalWCat19 Optical-spectroscopic SDSS Catalog. We derive cosmological constraints on the matter density, ${{\rm{\Omega }}}_{m}$ , and the amplitude of fluctuations, ${\sigma }_{8}$ , using ${\mathtt{GalWCat}}{\mathtt{19}}$ , a catalog of 1800 galaxy clusters we identified in the Sloan Digital Sky Survey-DR13 spectroscopic data set using our GalWeight technique to determine cluster membership. By analyzing a subsample of 756 clusters in a redshift range of 0.045 ≤ z ≤ 0.125 and virial masses of M ≥ 0.8 × 1014 ${h}^{-1}\ {M}_{\odot }$ with mean redshift of z = 0.085, we obtain ${{\rm{\Omega }}}_{m}={0.310}_{-0.027}^{+0.023}\pm 0.041$ (systematic) and ${\sigma }_{8}={0.810}_{-0.036}^{+0.031}\pm 0.035$ (systematic), with a cluster normalization relation of ${\sigma }_{8}=0.43{{\rm{\Omega }}}_{m}^{-0.55}$ . There are several unique aspects to our approach: we use the largest spectroscopic data set currently available, and we assign membership using the GalWeight technique, which we have shown to be very effective at simultaneously maximizing the number of bona fide cluster members while minimizing the number of contaminating interlopers. Moreover, rather than employing scaling relations, we calculate cluster masses individually using the virial mass estimator. Since ${\mathtt{GalWCat}}{\mathtt{19}}$ is a low-redshift cluster catalog we do not need to make any assumptions about evolution either in cosmological parameters or in the properties of the clusters themselves. Our constraints on ${{\rm{\Omega }}}_{m}$ and ${\sigma }_{8}$ are consistent and very competitive with those obtained from non-cluster abundance cosmological probes such as cosmic microwave background, baryonic acoustic oscillation (BAO), and supernovae. The joint analysis of our cluster data with Planck18+BAO+Pantheon gives ${{\rm{\Omega }}}_{m}={0.315}_{-0.011}^{+0.013}$ and ${\sigma }_{8}={0.810}_{-0.010}^{+0.011}$ .

Keywords: Galaxy clusters, Cosmological models, Large-scale structure of the universe, Galaxy cluster counts, Cosmological parameters
Spectroscopic Monitoring of Rapidly Rotating Early-type Stars in the Pleiades Cluster. Radial velocities for the early-type stars in the Pleiades cluster have always been challenging to measure because of the significant rotational broadening of the spectral lines. The large scatter in published velocities has led to claims that many are spectroscopic binaries, and in several cases, preliminary orbital solutions have been proposed. To investigate these claims, we obtained and report here velocity measurements for 33 rapidly rotating B, A, and early F stars in the Pleiades region, improving significantly on the precision of the historical velocities for most objects. With one or two exceptions, we do not confirm any of the previous claims of variability, and we also rule out all four of the previously published orbital solutions, for HD 22637, HD 23302, HD 23338, and HD 23410. We do find HD 22637 to be a binary but with a different period (71.8 days). HD 23338 is likely a binary as well, with a preliminary 8.7 yr period also different from the one published. Additionally, we report a 3635 day orbit for HD 24899, another new spectroscopic binary in the cluster. From the 32 bona fide members in our sample, we determine a mean radial velocity for the Pleiades of $5.79\pm 0.24\,\mathrm{km}\,{{\rm{s}}}^{-1}$ , or $5.52\pm 0.31\,\mathrm{km}\,{{\rm{s}}}^{-1}$ when objects with known visual companions are excluded. Adding these astrometric binaries to the new spectroscopic ones, we find a lower limit to the binary fraction among the B and A stars of 37%. In addition to the velocities, we measure $v\sin i$ for all stars, ranging between 69 and 317 $\mathrm{km}\,{{\rm{s}}}^{-1}$ .

Keywords: Binary stars, Radial velocity, Spectroscopic binary stars, Stellar rotation, Open star clusters, Visual binary stars
Inclination Excitation of Solar System Debris Disk Due to Stellar Flybys. Most stars form in clusters where relatively close encounters with other stars are common and can leave imprints on the orbital architecture of planetary systems. In this paper, we investigate the inclination excitation of debris disk particles due to such stellar encounters. We derive an analytical expression that describes inclination excitation in the hierarchical limit where the stellar flyby is distant. We then obtain numerical results for the corresponding particle inclination distribution in the nonhierarchical regime using a large ensemble of N-body simulations. For encounters with expected parameters, we find that the bulk inclination of the disk particles remains low. However, a distinct high-inclination population is produced by prograde stellar encounters for particles with final pericenter distances above 50 au. The maximum extent it of the inclination distribution scales with the inclination of the encounter $\sin ({i}_{s})$ for massive star flybys with low incoming velocity. The inclination distribution of observed trans-Neptunian objects places constraints on the dynamical history of our solar system. For example, these results imply an upper limit on product of the number density n of the solar birth cluster and the Sun's residence time τ of the form nτ ≲ 8 × 104 Myr pc-3. Stronger constraints can be derived with future observational surveys of the outer solar system.

Keywords: Solar system, Kuiper belt, Solar system astronomy
On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model Atmosphere Analysis of Hot White Dwarfs from SDSS DR12. As they evolve, white dwarfs undergo major changes in surface composition, a phenomenon known as spectral evolution. In particular, some stars enter the cooling sequence with helium atmospheres (type DO) but eventually develop hydrogen atmospheres (type DA), most likely through the upward diffusion of residual hydrogen. Our empirical knowledge of this process remains scarce: the fractions of white dwarfs that are born helium rich and that experience the DO-to-DA transformation are poorly constrained. We tackle this issue by performing a detailed model-atmosphere investigation of 1806 hot ( ${T}_{\mathrm{eff}}$ ≥ 30,000 K) white dwarfs observed spectroscopically by the Sloan Digital Sky Survey. We first introduce our new generations of model atmospheres and theoretical cooling tracks, both appropriate for hot white dwarfs. We then present our spectroscopic analysis, from which we determine the atmospheric and stellar parameters of our sample objects. We find that ∼24% of white dwarfs begin their degenerate life as DO stars, among which ∼2/3 later become DA stars. We also infer that the DO-to-DA transition occurs at substantially different temperatures (75,000 K &gt; ${T}_{\mathrm{eff}}$ &gt; 30,000 K) for different objects, implying a broad range of hydrogen content within the DO population. Furthermore, we identify 127 hybrid white dwarfs, including 31 showing evidence of chemical stratification, and we discuss how these stars fit in our understanding of the spectral evolution. Finally, we uncover significant problems in the spectroscopic mass scale of very hot ( ${T}_{\mathrm{eff}}$ &gt; 60,000 K) white dwarfs.

Keywords: Atmospheric composition, White dwarf stars, Stellar atmospheres, Late stellar evolution
Cause and Kinematics of a Jetlike CME. In this article, we present the multiviewpoint and multiwavelength analysis of an atypical solar jet based on data from Solar Dynamics Observatory, SOlar and Heliospheric Observatory, and Solar TErrestrial RElations Observatory. It is generally believed that coronal mass ejections (CMEs) develop from the large-scale solar eruptions in the lower atmosphere. However, the kinematical and spatial evolution of the jet on 2013 April 28 suggests that the jet was clearly associated with a narrow CME with a width of ≈25° and speed of ≈450 km s-1. To better understand the link between the jet and the CME, we performed a coronal potential field extrapolation from the line-of-sight magnetogram of the active region. The extrapolations suggest that the jet eruption follows the same path of the open magnetic field lines from the source region, which provides a route for the jet material to escape from the solar surface toward the outer corona.

Keywords: Solar activity, The Sun, Solar coronal mass ejections, Solar magnetic fields
ALMA Evidence for Ram Pressure Compression and Stripping of Molecular Gas in the Virgo Cluster Galaxy NGC 4402. High-resolution (1″ × 2″) Atacama Large Millimeter Array CO(2-1) observations of the ram pressure stripped galaxy NGC 4402 in the Virgo cluster show some of the clearest evidence yet for the impacts of ram pressure on the molecular interstellar medium (ISM) of a galaxy. The eastern side of the galaxy at r ∼ 4.5 kpc, upon which ram pressure is incident, has a large (width ∼1 kpc, height ∼1 kpc above the disk midplane) extraplanar plume of molecular gas and dust. Molecular gas in the plume region shows distinct noncircular motions in the direction of the ram pressure; the kinematic offset of up to 60 km s-1 is consistent with acceleration by ram pressure. We also detect a small amount of gas in clouds below the plume that are spatially and kinematically distinct from the surrounding medium, and appear to be decoupled from the stripped ISM. We propose that diffuse molecular gas is directly stripped but giant molecular cloud (GMC) density gas is not directly stripped, and so decouples from lower density stripped gas. However, GMCs become effectively stripped on short timescales. We also find morphological and kinematic signatures of ram pressure compression of molecular gas in a region of intense star formation on the leading side at r ∼ 3.5 kpc. We propose that the compressed and stripped zones represent different evolutionary stages of the ram pressure interaction, and that feedback from star formation in the compressed zone facilitates the effective stripping of GMCs by making the gas cycle rapidly to a lower density diffuse state.

Keywords: Galaxy clusters, Molecular gas, Virgo Cluster, Giant molecular clouds, Galaxy evolution, Interstellar medium, Diffuse molecular clouds
A Numerical Scheme for General Relativistic Radiation Magnetohydrodynamics Based on Solving a Grid-based Boltzmann Equation. We develop a general relativistic radiation magnetohydrodynamics (GR-RMHD) code INAZUMA in which the time-dependent radiation transfer equation (frequency-integrated Boltzmann equation) is solved in curved spacetime. The Eddington tensor is derived from the specific intensity, and we solve the zeroth and first moment equations in order to update the radiation fields. Therefore, our code can solve the radiation field around relativistic compact objects more appropriately than an approximation method like the M1 closure scheme. The numerical scheme of magnetohydrodynamics is the same as that of our previous code. In some test calculations for propagating radiation and radiation hydrodynamics in flat spacetime, our code shows similar results to our previous work. Radiation propagation in curved spacetime is also properly solved for. We also show the radiation transport from the super-Eddington accretion disk around the black hole. The disk structure, such as the density, velocity, and temperature, is fixed by the model obtained using the GR-RMHD simulation with the M1 method. We found that the difference between our scheme and the M1 method appears in the optically thin outflow region around the rotation axis while the radiation field is almost the same in the optically thick disk region.

Keywords: Accretion, Radiative magnetohydrodynamics, General relativity
Rocklines as Cradles for Refractory Solids in the Protosolar Nebula. In our solar system, terrestrial planets and meteoritical matter exhibit various bulk compositions. To understand this variety of compositions, formation mechanisms of meteorites are usually investigated via a thermodynamic approach that neglects the processes of transport throughout the protosolar nebula. Here, we investigate the role played by rocklines (condensation/sublimation lines of refractory materials) in the innermost regions of the protosolar nebula to compute the composition of particles migrating inward toward the disk as a function of time. To do so, we utilize a one-dimensional accretion disk model with a prescription for dust and vapor transport, sublimation, and recondensation of refractory materials (ferrosilite, enstatite, fayalite, forsterite, iron sulfide, metal iron, and nickel). We find that the diversity of the bulk composition of cosmic spherules, chondrules, and chondrites can be explained by their formation close to rocklines, suggesting that solid matter is concentrated in the vicinity of these sublimation/condensation fronts. Although our model relies a lot on the number of considered species and the availability of thermodynamic data governing state changes, it suggests that rocklines played a major role in the formation of small and large bodies in the innermost regions of the protosolar nebula. Our model gives insights on the mechanisms that might have contributed to the formation of Mercury's large core.

Keywords: Meteorite composition, Chondrites, Protoplanetary nebulae, Chondrules, Chemical abundances, Solar system terrestrial planets, Protoplanetary disks, Mercury (planet), Micrometeorites, Planet formation
Infrared Color Separation between Thin-shelled Oxygen-rich and Carbon-rich AGB Stars. We present 43 GHz VLA spectra for 51 AGB sources with the goal of verifying an infrared (IR) color cut intended to separate carbon-rich (C) and oxygen-rich (O) AGB sources throughout the Galaxy. The color cut is a simple line in the [Ks] - [A] versus [A] - [E] color-color diagram based on 2MASS and MSX photometry, and was originally derived from SiO detection rates in the Bulge Asymmetries and Dynamical Evolution (BAaDE) sample. The division is fully supported by the spectra presented here, which show that SiO maser detections lie on the O-rich side, and SiO nondetections and a single HC3N detection are found on the C-rich side of the division. We further compare the color cut with classifications of the sources based on Low-Resolution Spectra from the Infrared Astronomical Satellite, and find good agreement, verifying that the division is a reliable and efficient method for differentiating O- and C-rich AGB sources. These observations also demonstrate that single lines detected in the BAaDE survey around 42.9 GHz are almost certainly the 29SiO v = 0 line. SiO maser sources where this rare isotopologue transition is brighter than the dominant 28SiO lines have not been reported before, and our observations show that these sources can reverse their behavior such that the typical ratios of 28SiO and 29SiO are restored within a few years.

Keywords: Radio spectroscopy, Carbon stars, Silicon monoxide masers, Circumstellar masers, Asymptotic giant branch stars
On the Stabilization of a Twisted Magnetic Flux Tube. The linear magnetohydrodynamic stability of a shielding magnetic flux rope with a surface current under coronal solar conditions is analyzed in the framework of an energy principle. The equation describing the potential energy change induced by disturbances of the equilibrium was derived. It has been shown that the surface reverse current shielding the azimuthal component of the magnetic field lines outside a flux rope stabilizes the development of kink- and flute-type instabilities in the long-wavelength limit independently of the cross-sectional radial profile of current density. Kink modes are the most unstable ones as their generation requires less energy than other modes. Based on the obtained dispersion relation for kink oscillations, we proposed a new expression for the determination of magnetic field components of the twisted loop.

Keywords: Space plasmas, Magnetohydrodynamics
Synthetic Spectra of Rotating Stars. Many early-type stars have oblate surfaces, spatial temperature variations, and spectral line broadening that indicate large rotational velocities. Rotation ought to have a significant effect on the full spectra of such stars. To infer structural and life history parameters from their spectra, one must integrate specific intensity over the two-dimensional surfaces of corresponding stellar models. Toward this end, we offer Paint the Atmospheres of Rotating Stars—an integration scheme based on models that incorporate solid body rotation, Roche mass distribution, and collinearity of gravity and energy flux. The scheme features a closed-form expression for the azimuthal integral, a high-order numerical approximation of the longitudinal integral, and a precise calculation of surface effective temperature at rotation rates up to 99.9% of the Keplerian limit. Extensions of the scheme include synthetic color-magnitude diagrams and planetary transit curves.

Keywords: Stellar rotation, Early-type stars, Computational methods, Stellar effective temperatures