Sazuna/UAT_keywords huggingface dataset:
An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-ultraviolet Extinction and Its R-dependence. We produce a set of 72 NIR-through-UV extinction curves by combining new Hubble Space Telescope/STIS optical spectrophotometry with existing International Ultraviolet Explorer spectrophotometry (yielding gapless coverage from 1150 to 10000 Å) and NIR photometry. These curves are used to determine a new, internally consistent NIR-through-UV Milky Way mean curve and to characterize how the shapes of the extinction curves depend on R(V). We emphasize that while this dependence captures much of the curve variability, considerable variation remains that is independent of R(V). We use the optical spectrophotometry to verify the presence of structure at intermediate wavelength scales in the curves. The fact that the optical-through-UV portions of the curves are sampled at relatively high resolution makes them very useful for determining how extinction affects different broadband systems, and we provide several examples. Finally, we compare our results to previous investigations. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program 13760.

Keywords: Interstellar dust, Interstellar dust extinction, Interstellar reddening, Interstellar absorption, Interstellar dust processes, Interstellar scattering
Tidal Destruction in a Low-mass Galaxy Environment: The Discovery of Tidal Tails around DDO 44. We report the discovery of a ≳1° (∼50 kpc) long stellar tidal stream emanating from the dwarf galaxy DDO 44, a likely satellite of Local Volume galaxy NGC 2403 located ∼70 kpc in projection from its companion. NGC 2403 is a roughly Large Magellanic Cloud (LMC) stellar-mass galaxy 3 Mpc away, residing at the outer limits of the M81 group. We are mapping a large region around NGC 2403 as part of our Magellanic Analogs’ Dwarf Companions and Stellar Halos survey, reaching point-source depths (90% completeness) of (g, i) = (26.5, 26.2). Density maps of old, metal-poor RGB stars reveal tidal streams extending on two sides of DDO 44, with the streams directed toward NGC 2403. We estimate total luminosities of the original DDO 44 system (dwarf and streams combined) to be M  i,tot = -13.4 and M  g,tot = -12.6, with ∼25%-30% of the luminosity in the streams. Analogs of ∼LMC-mass hosts with massive tidally disrupting satellites are rare in the Illustris simulations, especially at large separations such as that of DDO 44. The few analogs that are present in the models suggest that even low-mass hosts can efficiently quench their massive satellites. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: Dwarf galaxies, Galaxy interactions, Galaxy stellar halos, Tidal tails, Galaxy photometry, Dwarf spheroidal galaxies
Fast Radio Bursts from Magnetars Born in Binary Neutron Star Mergers and Accretion Induced Collapse. Recently born magnetars are promising candidates for the engines powering fast radio bursts (FRBs). The focus thus far has been placed on millisecond magnetars born in rare core-collapse explosions, motivated by the star-forming dwarf host galaxy of the repeating FRB 121102, which is remarkably similar to the hosts of superluminous supernovae and long gamma-ray bursts. However, long-lived magnetars may also be created in binary neutron star (BNS) mergers, in the small subset of cases with a sufficiently low total mass for the remnant to avoid collapse to a black hole, or in the accretion-induced collapse (AIC) of a white dwarf. A BNS or AIC FRB channel will be characterized by distinct host galaxy and spatial offset distributions which we show are consistent with the recently reported FRB 180924, localized by the Australian Square Kilometre Array Pathfinder to a massive quiescent host galaxy with an offset of about 1.4 effective radii. Using models calibrated to FRB 121102, we make predictions for the dispersion measure, rotation measure, and persistent radio emission from magnetar FRB sources born in BNS mergers or AIC, and show these are consistent with upper limits from FRB 180924. Depending on the rate of AIC, and the fraction of BNS mergers leaving long-lived stable magnetars, the birth rate of repeating FRB sources associated with older stellar populations could be comparable to that of the core-collapse channel. We also discuss potential differences in the repetition properties of these channels, as a result of differences in the characteristic masses and magnetic fields of the magnetars.

Keywords: Magnetars, Radio bursts, Gamma-ray bursts, Gravitational waves
Toward Early-type Eclipsing Binaries as Extragalactic Milestones. I. Physical Parameters of OGLE-LMC-ECL-22270 and OGLE-LMC-ECL-06782. In this first paper of a series, we describe our project to calibrate the distance determination method based on early-type binary systems. The final objective is to measure accurate, geometrical distances to galaxies beyond the Magellanic Clouds with a precision of 2%. We start with the analysis of two early-type systems for which we have collected all the required spectroscopic and photometric data. Apart from catalog publications, these systems have not been studied yet, and this is the first time the modeling of light and radial velocity curves is performed for them. From the analysis we obtained precise physical parameters of the components, including the masses measured with a precision of 0.6%-1% and radii measured with a precision of 0.4%-3%. For one system we determined the (V-K) color and estimated the distance using the bolometric flux scaling method (DM = 18.47 ± 0.15 mag), which agrees well with our accurate determination of the distance to the Large Magellanic Cloud from late-type giants. For the same system we determined the surface brightness of individual stars using our model, and checked that it is consistent with a recent surface-brightness-color relation. We compared our results with evolution theory models of massive stars and found they agree in general; however, models with higher overshooting values give more consistent results. The age of the system was estimated to range from 11.7 to 13.8 Myr, depending on the model.

Keywords: Early-type stars, Large Magellanic Cloud, Distance indicators, Detached binary stars, Eclipsing binary stars, Stellar evolution
Characteristics of Magnetoacoustic Waves and Coronal Seismology. We model fast magnetohydrodynamic sausage and kink wave characteristics propagating in solar slab-like plasma structures. By implementing Cartesian coordinates, explicit expressions are provided governing the dependence of the frequency, damping, damping time, phase, and group speeds of fast sausage and kink waves on the wavenumber and density contrasts of solar slab-like plasmas. Explicit expressions are presented through equilibrium conditions and physical parameters controlling the plasma structure. Solutions of the explicit expressions are compared with numerical results. The overlap of curves proves adequate for the robustness of the explicit expressions. Kink modes possess higher frequencies compared to sausage modes in the leaky regime, while the sausage mode phase speed increases more rapidly compared to the kink speed. This explains the higher group speeds of sausage waves compared to kink waves around the cutoff. Sausage waves damp quicker compared with kink waves. The damping is inversely proportional to the mode number. As the damping time is directly proportional with the wavenumber, the damping time is much higher around the cutoff frequency compared to the long wavelength limit. The presented expressions prove adequate for coronal seismology, where, as the magnetoacoustic oscillations damp and disappear, the local and neighboring physical parameters and conditions could be estimated. As leaky kink modes live longer than sausage modes, they have a higher chance of being observed while transporting energy to a broader region. Sausage modes penetrate less due to fast damping providing higher heating rates in shorter ranges. Both modes contribute to coronal heating in various scales.

Keywords: The Sun, Magnetic fields, Magnetohydrodynamics
Triangulum-Andromeda Overdensity: a Region with a Complex Stellar Population. The Triangulum-Andromeda (TriAnd) overdensity is a distant structure of the Milky Way located in the second Galactic quadrant well below the Galactic plane. Since its discovery, its nature has been under discussion, whether it could be old perturbations of the Galactic disk or the remains of a disrupted former dwarf galaxy. In this study, we investigate the kinematics and chemical composition in 13 stars selected as TriAnd candidates from Two Micron All Sky Survey photometry. The sample was observed using the GRACES high-resolution spectrograph attached to the Gemini North telescope. Based on radial velocities obtained from the spectra and the astrometric data from Gaia, three different kinematic criteria were used to classify our sample stars as belonging to the TriAnd overdensity. The TriAnd confirmed members in our sample span a range in metallicities, including two metal-poor stars ([Fe/H] ∼ -1.3 dex). We show that the adopted kinematical classification also chemically segregates TriAnd and non-TriAnd members of our sample, indicating a unique chemical pattern of the TriAnd stars. Our results indicate different chemical patterns for the [Na/Fe], [Al/Fe], [Ba/Fe], and [Eu/Fe] ratios in the TriAnd stars when compared to the chemical pattern of the local disk; the paucity of studies chemically characterizing the outer disk population of the Milky Way is the main obstacle in establishing that the TriAnd population is chemically similar to field stars in the outer disk. But the TriAnd chemical pattern is reminiscent of that found in outer disk open clusters, although the latter are significantly more metal-rich than TriAnd.

Keywords: Stellar kinematics, Milky Way disk, Chemical abundances
Multiple Populations in Globular Clusters: Unified Efforts from Stellar Evolution and Chemical Evolution Models. Recent stellar evolution models for globular clusters (GCs) in a multiple population paradigm suggest that horizontal-branch (HB) morphology and the mean period of type ab RR Lyrae variables are mostly determined by He and CNO abundances and relative ages for subpopulations. These parameters are also provided by chemical evolution models constructed to reproduce the Na-O anticorrelation. Therefore, a consistency check is possible between the synthetic HB and chemical evolution models. Furthermore, by combining them, a better constraint might be attained for star formation history and chemical abundances of subpopulations in GCs. We find, from such efforts made for four GCs, M4, M5, M15, and M80, that consistent results can be obtained from these two independent studies. In our unified model, He and Na abundances gradually increase over the generation, and, therefore, the various extensions observed in both HB morphology and the Na-O chemical pattern depend on the presence of later generation stars after the second generation. It is schematically shown that this observed diversity, however, would not be naturally explained by the models requiring dilution. Further spectroscopic observations are required, for metal-poor GCs in particular, to obtain a more detailed constraint from this approach.

Keywords: Globular star clusters, Horizontal branch, Chemical abundances
Carbon and Oxygen Isotopic Ratios. II. Semiregular Variable M Giants. Carbon and oxygen isotopic ratios are reported for a sample of 51 SRb- and Lb-type variable asymptotic giant branch stars. Vibration-rotation first- and second-overtone CO lines in 1.5-2.5 μm spectra were measured to derive isotopic ratios for 12C/13C, 16O/17O, and 16O/18O. Comparisons with previous measurements for individual stars and with various samples of evolved stars, as available in the extant literature, are discussed. Using the oxygen isotopic ratios, the masses of the SRb stars can be derived. Combining the masses with Gaia luminosities, the SRb stars are shown to be antecedents of the Mira variables. The limiting parameters where plane-parallel, hydrostatic equilibrium model atmospheres can be used for abundance analysis of M giants are explored.

Keywords: High resolution spectroscopy, Isotopic abundances, Late stellar evolution, Asymptotic giant branch stars, Semi-regular variable stars, Long period variable stars, Stellar nucleosynthesis
A Population of Neutron Star Ultraluminous X-Ray Sources with a Helium Star Companion. It was recently proposed that a significant fraction of ultraluminous X-ray sources (ULXs) actually host a neutron star (NS) accretor. We have performed a systematic study on the NS ULX population in Milky Way-like galaxies, by combining binary population synthesis and detailed stellar evolution calculations. Besides a normal star, the ULX donor can be a helium star (the hydrogen envelope of its progenitor star was stripped during previous common envelope evolution) if the NS is accreting at a super-Eddington rate via Roche lobe overflow. We find that the NS-helium star binaries can significantly contribute to the ULX population, with the overall number of about several in a Milky Way-like galaxy. Our calculations show that such ULXs are generally close systems with orbital period distribution peaked at ∼0.1 day (with a tail up to ∼100 days), and the helium stars have relatively low masses distributing with a maximum probability at ∼1M ⊙.

Keywords: Neutron stars, X-ray binary stars, Binary stars, Stellar evolution
Droplets. II. Internal Velocity Structures and Potential Rotational Motions in Pressure-dominated Coherent Structures. We present an analysis of the internal velocity structures of the newly identified sub-0.1 pc coherent structures, droplets, in L1688 and B18. By fitting 2D linear velocity fields to the observed maps of velocity centroids, we determine the magnitudes of linear velocity gradients and examine the potential rotational motions that could lead to the observed velocity gradients. The results show that the droplets follow the same power-law relation between the velocity gradient and size found for larger-scale dense cores. Assuming that rotational motion giving rise to the observed velocity gradient in each core is a solid-body rotation of a rotating body with a uniform density, we derive the “net rotational motions” of the droplets. We find a ratio between rotational and gravitational energies, β, of ∼0.046 for the droplets, and when including both droplets and larger-scale dense cores, we find β ∼ 0.039. We then examine the alignment between the velocity gradient and the major axis of each droplet, using methods adapted from the histogram of relative orientations introduced by Soler et al. We find no definitive correlation between the directions of velocity gradients and the elongations of the cores. Lastly, we discuss physical processes other than rotation that may give rise to the observed velocity field.

Keywords: Interstellar dynamics, Star forming regions, Molecular clouds, Star formation, Radio astronomy
A New Formation Model for ω Centauri: A Complex Interplay of Astrophysical Processes. We investigate the formation processes of the Galactic globular cluster (GC) ω Cen with multiple stellar populations based on our original hydrodynamical simulations with chemical enrichment by Type II supernovae (SNe II), asymptotic giant branch (AGB) stars, and neutron star mergers (NSMs). Multiple stellar populations with a wide range of [Fe/H] can be formed from rather massive and compact molecular clouds with a mass of ≈2 × 107 M ⊙ in the central region of its dwarf galaxy within less than a few hundred megayears. Gas ejected from SNe II and AGB stars can mix well to form new stars with higher He abundances (Y) and higher [Fe/H]. The He-rich stars are strongly concentrated in the GC’s central region so that the GC can show a steep negative gradient of Y. Relative ratios of light elements to Fe show bimodal distributions for a given [Fe/H] owing to star formation from original gas and AGB ejecta. [La/Fe] and [Ba/Fe] can rapidly increase until [Fe/H] ∼ -1.5 and then decrease owing to Fe ejection from SNe II. Although AGB ejecta can be almost fully retained in the intracluster medium, NSM ejecta can be retained only partially. This difference in the retention capability is responsible for the observed unique [Eu/Fe]-[Fe/H] and [La/Eu]-[Fe/H] relations in ω Cen. The observed [O/Na]-[Fe/H] relation and radial [Fe/H] gradient are yet to be well reproduced in the present model. We briefly discuss how the results change for different yields of AGB stars and SNe II.

Keywords: Globular star clusters, Neutron stars, Asymptotic giant branch, Chemical abundances, Galaxy abundances
The Interplay of Magnetically Dominated Turbulence and Magnetic Reconnection in Producing Nonthermal Particles. Magnetized turbulence and magnetic reconnection are often invoked to explain the nonthermal emission observed from a wide variety of astrophysical sources. By means of fully kinetic 2D and 3D particle-in-cell simulations, we investigate the interplay between turbulence and reconnection in generating nonthermal particles in magnetically dominated (or, equivalently, “relativistic”) pair plasmas. A generic by-product of the turbulence evolution is the generation of a nonthermal particle spectrum with a power-law energy range. The power-law slope p is harder for larger magnetizations and stronger turbulence fluctuations, and it can be as hard as p ≲ 2. The Larmor radius of particles at the high-energy cutoff is comparable to the size l of the largest turbulent eddies. Plasmoid-mediated reconnection, which self-consistently occurs in the turbulent plasma, controls the physics of particle injection. Then, particles are further accelerated by stochastic scattering off turbulent fluctuations. The work done by parallel electric fields—naturally expected in reconnection layers—is responsible for most of the initial energy increase and is proportional to the magnetization σ of the system, while the subsequent energy gain, which dominates the overall energization of high-energy particles, is powered by the perpendicular electric fields of turbulent fluctuations. The two-stage acceleration process leaves an imprint in the particle pitch-angle distribution: low-energy particles are aligned with the field, while the highest-energy particles move preferentially orthogonal to it. The energy diffusion coefficient of stochastic acceleration scales as D  γ  ∼ 0.1σ(c/l)γ 2, where γ is the particle Lorentz factor. This results in fast acceleration timescales t acc ∼ (3/σ)l/c. Our findings have important implications for understanding the generation of nonthermal particles in high-energy astrophysical sources.

Keywords: High energy astrophysics, Plasma physics, Plasma astrophysics, Non-thermal radiation sources, Particle astrophysics
New Limits on the Low-frequency Radio Transient Sky Using 31 hr of All-sky Data with the OVRO-LWA. We present the results of the first transient survey from the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) using 31 hr of data, in which we place the most constraining limits on the instantaneous transient surface density at timescales of 13 s to a few minutes and at frequencies below 100 MHz. The OVRO-LWA is a dipole array that images the entire viewable hemisphere with 58 MHz of bandwidth from 27 to 84 MHz at 13 s cadence. No transients are detected above a 6.5σ flux density limit of 10.5 Jy, implying an upper limit to the transient surface density of 2.5 × 10-8 deg-2 at the shortest timescales probed, which is orders of magnitude deeper than has been achieved at sub-100 MHz frequencies and comparable flux densities to date. The nondetection of transients in the OVRO-LWA survey, particularly at minutes-long timescales, allows us to place further constraints on the rate of the potential population of transients uncovered by Stewart et al. From their transient rate, we expect a detection of {8.4}-8.0+31.8 events, and the probability of our null detection is {1.9}-1.9+644× {10}-3, ruling out a transient rate &gt;1.4 × 10-4 days-1 deg-2 with 95% confidence at a flux density limit of 18.1 Jy, under the assumption of a flat spectrum and wide bandwidth. We discuss the implications of our nondetection for this population and further constraints that can be made on the source spectral index, intrinsic emission bandwidth, and resulting luminosity distribution.

Keywords: Radio astronomy, Radio interferometry, Non-thermal radiation sources, Radio transient sources
The KMOS<SUP>3D</SUP> Survey: Data Release and Final Survey Paper. We present the completed KMOS3D survey, an integral field spectroscopic survey of 739 {log}({M}\star /{M}☉ )&gt; 9 galaxies at 0.6 &lt; z &lt; 2.7 using the K-band Multi Object Spectrograph (KMOS) at the Very Large Telescope. The KMOS3D survey provides a population-wide census of kinematics, star formation, outflows, and nebular gas conditions both on and off the star-forming galaxy main sequence through the spatially resolved and integrated properties of Hα, [N II], and [S II] emission lines. We detect Hα emission for 91% of galaxies on the main sequence of star formation and 79% overall. The depth of the survey has allowed us to detect galaxies with star formation rates below 1 M ☉ yr-1, as well as to resolve 81% of detected galaxies with ≥3 resolution elements along the kinematic major axis. The detection fraction of Hα is a strong function of both color and offset from the main sequence, with the detected and nondetected samples exhibiting different spectral energy distribution shapes. Comparison of Hα and UV+IR star formation rates reveal that dust attenuation corrections may be underestimated by 0.5 dex at the highest masses ({log}({M}\star /{M}☉ )&gt; 10.5). We confirm our first year results of a high rotation-dominated fraction (monotonic velocity gradient and v rot/{σ }0&gt; \sqrt{3.36}) of 77% for the full KMOS3D sample. The rotation-dominated fraction is a function of both stellar mass and redshift, with the strongest evolution measured over the redshift range of the survey for galaxies with {log}({M}\star /{M}☉ )&lt; 10.5. With this paper, we include a final data release of all 739 observed objects (http://www.mpe.mpg.de/ir/KMOS3D). Based on observations obtained at the Very Large Telescope (VLT) of the European Southern Observatory (ESO), Paranal, Chile (ESO program IDS 092A-0091, 093.A-0079, 093.A-0079, 094.A-0217, 095.A-0047, 096.A-0025, 097.A-0028, 098.A-0045, 099.A-0013, 0100.A-0039, and 0101.A-0022).

Keywords: Disk galaxies, Surveys, Emission line galaxies, Galaxy kinematics, Galaxy evolution, High-redshift galaxies