Sazuna/UAT_keywords huggingface dataset:
A Low-velocity Bipolar Outflow from a Deeply Embedded Object in Taurus Revealed by the Atacama Compact Array. The first hydrostatic core, the first quasi-hydrostatic object formed during the star formation process, is still the observational missing link between the prestellar and protostellar phases, mainly due to its short lifetime. Although we have not established a clear method to identify this rare object, recent theoretical studies predict that the first core has millimeter continuum emission and low-velocity outflow with a wide opening angle. An extensive continuum/outflow survey toward a large number of "starless" cores in nearby star-forming regions works as a pathfinder. We observed 32 prestellar cores in Taurus with an average density of ≳105 cm-3 in 1.3 mm continuum and molecular lines using the Atacama Large Millimeter/submillimeter Array-Atacama Compact Array (ALMA-ACA) stand-alone mode. Among the targets, MC35-mm centered at one of the densest "starless" cores in Taurus has blueshifted/redshifted wings in the 12CO (2-1) line, indicating that there is a deeply embedded object driving molecular outflow. The observed velocities and sizes of the possible outflow lobes are 2-4 km s-1 and ∼2 × 103 au, respectively, and the dynamical time is calculated to be ∼103 yr. In addition to this, the core is one of the strongest N2D+ (3-2) emitters in our sample. All of the observed signatures do not conflict with any of the theoretical predictions about the first hydrostatic core so far, and thus MC35-mm is unique as the only first-core candidate in the Taurus molecular cloud.

Keywords: Protostars, Star formation, Collapsing clouds
Discovery of High-velocity Hα Emission in the Direction of the Fermi Bubble. Wisconsin H-Alpha Mapper observations reveal high-velocity Hα and [N II]λ6584 emission lines in the same direction and velocity as ultraviolet absorption-line features that have been previously associated with the biconical gamma-ray lobes known as the Fermi Bubbles. We measure an extinction-corrected intensity of ${I}_{{\rm{H}}\alpha }={0.84}_{-0.09}^{+0.10}\,\mathrm{Rayleigh}$ for emission with line center vLSR = -221 ± 3 km s-1, corresponding to an emission measure of $\mathrm{EM}={2.00}_{-0.63}^{+0.64}\,{\mathrm{cm}}^{-6}\,\mathrm{pc}$ . This emission arises at the same velocity as Hubble Space Telescope/Cosmic Origins Spectrograph observations of ultraviolet absorption features detected in the PDS 456 quasar sight line that passes through the northern bubble near l = 10°4, b = +11°2. We estimate the total column density of ionized gas in this velocity component to be $N({{\rm{H}}}^{+})=\left(3.28\pm 0.33\right)\times {10}^{18}\,{\mathrm{cm}}^{-2}$ . The comparison of ionized gas emission and absorption yields an estimate for the characteristic density of ne,c = 1.8 ± 0.6 cm-3 and a characteristic length of Lc = 0.56 ± 0.21 pc assuming 30% solar metallicity. For a temperature of ${T}_{e}={8500}_{-2600}^{+2700}\,{\rm{K}}$ —consistent with the measured line widths and [N II]/Hα line ratio—the gas has a thermal pressure of $p/k={{\rm{32,000}}}_{-14,000}^{+15,000}\,{\mathrm{cm}}^{-3}\,{\rm{K}}$ . Assuming the gas is ∼6.5 kpc distant, the derived density and pressure appear to be anomalously high for gas ∼1.3 kpc above the Galactic midplane. The large thermal pressure is comparable to both a hot halo or Fermi Bubble model, but suggest that the Hα arises in an overpressurized zone.

Keywords: Galactic winds, Galactic center, Warm ionized medium, Interstellar emissions, Interstellar absorption, Interstellar medium
Lessons on Star-forming Ultra-diffuse Galaxies from the Stacked Spectra of the Sloan Digital Sky Survey. We investigate the on-average properties for 28 star-forming ultra-diffuse galaxies (UDGs) located in low-density environments, by stacking their spectra from the Sloan Digital Sky Survey. These relatively isolated UDGs, with stellar masses of ${\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })\sim 8.57\pm 0.29$ , have the on-average total stellar metallicity [M/H] ∼ -0.82 ± 0.14, iron metallicity [Fe/H] ∼ -1.00 ± 0.16, stellar age t* ∼ 5.2 ± 0.5 Gyr, α-enhancement [α/Fe] ∼ 0.24 ± 0.10, and oxygen abundance 12+log(O/H) ∼ 8.16 ± 0.06, as well as central stellar velocity dispersion 54 ± 12 km s-1. On the star formation rate versus stellar mass diagram, these UDGs are located lower than the extrapolated star-forming main sequence from the massive spirals, but roughly follow the main sequence of low-surface-brightness dwarf galaxies. We find that these star-forming UDGs are not particularly metal-poor or metal-rich for their stellar masses, as compared with the metallicity-mass relations of the nearby typical dwarfs. With the UDG data of this work and previous studies, we also find a coarse correlation between [Fe/H] and magnesium-element enhancement [Mg/Fe] for UDGs: [Mg/Fe] ≃ -0.43(±0.26) [Fe/H] -0.14(±0.40).

Keywords: Dwarf galaxies, Galaxy evolution, Spectroscopy
Limits on the Spin-Orbit Angle and Atmospheric Escape for the 22 Myr Old Planet AU Mic b. We obtained spectra of the pre-main-sequence star AU Microscopii during a transit of its Neptune-sized planet to investigate its orbit and atmosphere. We used the high-dispersion near-infrared spectrograph InfraRed Doppler (IRD) on the Subaru telescope to detect the Doppler "shadow" from the planet and constrain the projected stellar obliquity. Modeling of the observed planetary Doppler shadow suggests a spin-orbit alignment of the system ( $\lambda =-{4.7}_{-6.4}^{+6.8}$ deg), but additional observations are needed to confirm this finding. We use both the IRD data and spectra obtained with NIRSPEC on Keck II to search for absorption in the 1083 nm line of metastable triplet He I by the planet's atmosphere and place an upper limit for the equivalent width of 3.7 mÅ at 99% confidence. With this limit and a Parker wind model we constrain the escape rate from the atmosphere to $\lt 0.15\mbox{--}0.45$ M⊕ Gyr-1, comparable to the rates predicted by an X-ray and ultraviolet energy-limited escape calculation and hydrodynamic models, but refinement of the planet mass is needed for rigorous tests. * Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan, and the W. M. Keck Observatory, which is supported by the W. M. Keck Foundation and operated by the California Institute of Technology, the University of California and the National Aeronautics and Space Administration.

Keywords: High resolution spectroscopy, Exoplanet evolution, Radial velocity
Axial Asymmetry Studies in Gaia Data Release 2 Yield the Pattern Speed of the Galactic Bar. Our recent studies of axial-symmetry breaking in the nearby (d &lt; 3 kpc) star counts are sensitive to the distortions of stellar orbits perpendicular and parallel to the orientation of the bar just within and beyond the outer Lindblad resonance (OLR) radius. Using the location of the sign flip in the left-right asymmetry in stars counts about the anticenter line to determine the OLR radius ROLR, and treating the bar as if it were a weakly nonaxisymmetric effect, we use ROLR and recent measurements of the Galactic rotation curve and the Sun-Galactic-center distance R0 to determine the pattern speed Ωp of the Galactic bar, as well as the Galactic corotation radius RCR. After removing the effect of the Large and Small Magellanic Clouds from our asymmetry measurement, we find that ROLR = (0.96 ± 0.03)R0 = 7.85 ± 0.25 kpc, Ωp = 49.3 ± 2.2 km s-1 kpc-1, RCR = (0.58 ± 0.04)R0 = 4.76 ± 0.27 kpc, revealing, as we shall show, that the Milky Way's bar is likely both weak and fast, though we also note possible evidence for non-steady-state effects in the bar region.

Keywords: Milky Way rotation, Galactic center, Milky Way dynamics, Galactic bulge
Formation of Mass Gap Objects in Highly Asymmetric Mergers. The LIGO/Virgo Collaboration (LVC) recently reported the detection of GW190814, a merger of a ${23}_{-0.9}^{+1.0}\,\,{M}_{\odot }$ primary black hole (BH), and a ${2.6}_{-0.08}^{+0.08}\,\,{M}_{\odot }$ secondary. The secondary's mass falls into the mass gap regime, which refers to the scarcity of compact objects in the mass range of 2-5 $\,{M}_{\odot }$ . The first clue to the formation of GW190814 lies in the fact that the primary is a very massive BH. We suggest that the secondary was born as a neutron star (NS) where a significant amount of the supernova ejecta mass from its formation remained bound to the binary due to the presence of the massive BH companion. The bound mass forms a circumbinary accretion disk, and its accretion onto the NS created a mass gap object. In this scenario, LIGO/Virgo will only detect mass gap objects in binary mergers with an extreme mass ratio. We also predict a correlation between the mass of the secondary and the mass of the primary in such asymmetric mergers. Our model can be tested with future data from the LVC's third observing run.

Keywords: Neutron stars, Ejecta, Supernova remnants, Compact objects, LIGO, Supernovae, Prior distribution, Astrophysical black holes
A Redshifted Inner Disk Atmosphere and Transient Absorbers in the Ultracompact Neutron Star X-Ray Binary 4U 1916-053. The very small accretion disks in ultracompact X-ray binaries are special laboratories in which to study disk accretion and outflows. We report on three sets of new (250 ks total) and archival (50 ks) Chandra/HETG observations of the "dipping" neutron star X-ray binary 4U 1916-053, which has an orbital period of P ≃ 50 minutes. We find that the bulk of the absorption in all three spectra originates in a disk atmosphere that is redshifted by v ≃ 220-290 km s-1, corresponding to the gravitational redshift at a radius of R ∼ 1200 GM/c2. This shift is present in the strongest, most highly ionized lines (Si XIV and Fe XXVI), with a significance of 5σ. Absorption lines observed during dipping events (typically associated with the outermost disk) instead display no velocity shifts and serve as a local standard of rest, suggesting that the redshift is intrinsic to an inner disk atmosphere and not due to radial motion in the galaxy or a kick. In two spectra, there is also evidence of a more strongly redshifted component that would correspond to a disk atmosphere at R ∼ 70 GM/c2; this component is significant at the 3σ level. Finally, in one spectrum, we find evidence of a disk wind with a blueshift of $v=-{1700}_{-1200}^{+1700}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . If real, this wind would require magnetic driving.

Keywords: Accretion, Neutron stars, High energy astrophysics
You Can't Always Get What You Want: The Impact of Prior Assumptions on Interpreting GW190412. GW190412 is the first observation of a black hole binary with definitively unequal masses. GW190412's mass asymmetry, along with the measured positive effective inspiral spin, allowed for inference of a component black hole spin: the primary black hole in the system was found to have a dimensionless spin magnitude between $0.17$ and $0.59$ (90% credible range). We investigate how the choice of priors for the spin magnitudes and tilts of the component black holes affect the robustness of parameter estimates for GW190412, and report Bayes factors across a suite of prior assumptions. Depending on the waveform family used to describe the signal, we find either marginal to moderate ( $2$ :1- $6$ :1) or strong (≳ $20$ :1) support for the primary black hole being spinning compared to cases where only the secondary is allowed to have spin. We show how these choices influence parameter estimates, and find the asymmetric masses and positive effective inspiral spin of GW190412 to be qualitatively, but not quantitatively, robust to prior assumptions. Our results highlight the importance of both considering astrophysically motivated or population-based priors in interpreting observations and considering their relative support from the data.

Keywords: Bayesian statistics, Binary stars, Black holes, Gravitational wave sources, Gravitational waves, LIGO, Stellar evolution
The Importance of Local Interstellar Conditions on the Galactic Cosmic-Ray Spectrum at Exoplanets. Galactic cosmic rays (GCRs) are highly energetic particles that can have significant effects on the atmospheres and potentially also surfaces of (exo)planets and moons. Their propagation through the Sun's heliosphere and their interaction with planetary bodies have been widely studied in the solar system (e.g., Earth, Mars, Venus, and Europa). There is currently much interest in exoplanetary science, particularly in terms of characterizing the potential habitability of exoplanetary environments. As a consequence of this, models have been developed to quantify the effect of GCRs on exoplanet systems. However, many such studies assume Earth-like (1 au) GCR fluxes. Here we will demonstrate why this is not a reasonable assumption. We briefly discuss the journey that GCRs make from their birth to the arrival at an exoplanet, and discuss the various implications this will have on GCR fluxes. We demonstrate the importance of understanding the specific local interstellar medium (ISM) that an exoplanetary system resides within, as this determines the size of the astrosphere of the host star. This has strong implications for the modulation of GCR fluxes throughout an astrosphere. We estimate how GCR proton fluxes at 1 au (from the Sun) would be different from current values if the solar system was embedded in a different ISM environment. Furthermore, we provide estimates of the wide range of possible GCR proton fluxes at the exoplanets Kepler-20f and Kepler-88c using previously published estimates for the local ISM parameters at these bodies.

Keywords: Galactic cosmic rays, Astrospheres, Habitable planets, Exoplanets
Insight-HXMT Firm Detection of the Highest-energy Fundamental Cyclotron Resonance Scattering Feature in the Spectrum of GRO J1008-57. We report on the observation of the accreting pulsar GRO J1008-57 performed by Insight-Hard X-ray Modulation Telescope (HXMT) at the peak of the source's 2017 outburst. Pulsations are detected with a spin period of 93.283(1) s. The pulse profile shows double peaks at soft X-rays, and only one peak above 20 keV. The spectrum is well described by the phenomenological models of X-ray pulsars. A cyclotron resonant scattering feature (CRSF) is detected with very high statistical significance at a centroid energy of ${E}_{\mathrm{cyc}}={90.32}_{-0.28}^{+0.32}$ keV, for the reference continuum and line models, HIGHECUT and GABS, respectively. Detection is very robust with respect to different continuum models. The line energy is significantly higher than what is suggested from previous observations, which provided very marginal evidence for the line. This establishes a new record for the centroid energy of a fundamental CRSF observed in accreting pulsars. We also discuss the accretion regime of the source during the Insight-HXMT observation.

Keywords: High mass x-ray binary stars, Magnetic fields, Pulsars
Discovery of the Black Hole X-Ray Binary Transient MAXI J1348-630. We report the first half-year monitoring of the new Galactic black hole candidate MAXI J1348-630, discovered on 2019 January 26 with the Gas Slit Camera on board the Monitor of All-sky X-ray Image (MAXI). During the monitoring period, the source exhibited two outburst peaks, where the first peak flux (at T = 14 days from the discovery of T = 0) was ∼4 Crab (2-20 keV) and the second one (at T = 132 days) was ∼0.4 Crab (2-20 keV). The source exhibited distinct spectral transitions between the high/soft and low/hard states and an apparent "q"-shape curve on the hardness-intensity diagram, both of which are well-known characteristics of black hole binaries (BHBs). Compared to other bright black hole transients, MAXI J1348-630 is characterized by its low disk temperature (∼0.75 keV at the maximum) and high peak flux in the high/soft state. The low peak temperature leads to a large innermost radius that is identified as the innermost stable circular orbit, determined by the black hole mass and spin. Assuming the empirical relation between the soft-to-hard transition luminosity (Ltrans) and the Eddington luminosity (LEdd), Ltrans/LEdd ≈ 0.02, and a face-on disk around a non-spinning black hole, the source distance and the black hole mass are estimated to be D ≈ 4 kpc and $\sim 7\left(D/4\,\mathrm{kpc}\right){M}_{\odot }$ , respectively. The black hole is more massive if the disk is inclined and the black hole is spinning. These results suggest that MAXI J1348-630 may host a relatively massive black hole among the known BHBs in our Galaxy.

Keywords: Black holes, High energy astrophysics, Compact objects, Stellar accretion disks, X-ray novae
Scintillation Can Explain the Spectral Structure of the Bright Radio Burst from SGR 1935+2154. The discovery of a fast radio burst (FRB) associated with a magnetar in the Milky Way by the Canadian Hydrogen Intensity Mapping Experiment FRB collaboration (CHIME/FRB) and the Survey for Transient Astronomical Radio Emission 2 has provided an unprecedented opportunity to refine FRB emission models. The burst discovered by CHIME/FRB shows two components with different spectra. We explore interstellar scintillation as the origin for this variation in spectral structure. Modeling a weak scattering screen in the supernova remnant associated with the magnetar, we find that a superluminal apparent transverse velocity of the emission region of &gt;9.5c is needed to explain the spectral variation. Alternatively, the two components could have originated from independent emission regions &gt;8.3 × 104 km apart. These scenarios may arise in "far-away" models where the emission originates from well beyond the magnetosphere of the magnetar (for example, through a synchrotron maser mechanism set up by an ultrarelativistic radiative shock), but not in "close-in" models of emission from within the magnetosphere. If further radio observations of the magnetar confirm scintillation as the source of the observed variation in spectral structure, this scattering model thus constrains the location of the emission region.

Keywords: Neutron stars, Magnetars, Radio bursts, Interstellar scattering
Impact Experiment on Asteroid (162173) Ryugu: Structure beneath the Impact Point Revealed by In Situ Observations of the Ejecta Curtain. An impact experiment was performed on the surface of the C-type asteroid (162173) Ryugu using an instrument called the Small Carry-on Impactor (SCI) carried by the Japan Aerospace Exploration Agency spacecraft Hayabusa2. Using a small camera separated from the spacecraft, we observed the development of the ejecta curtain formed by the SCI impact in situ. Based on the patterns appearing in the ejecta curtain, we evaluated the physical properties of large boulders and regolith grains on Ryugu. We found that the large boulders on the surface near the SCI impact point had a compressive strength consistent with the previous estimation of a tensile strength based on low thermal inertia observed for boulders on Ryugu. Furthermore, the ejecta curtain consisted of the boulders with a maximum size of several decimeters. Moreover, the filament structure was formed in the SCI ejecta curtain, strongly suggesting that the SCI impact ejecta curtain particles had a size range greater than one order of magnitude; a characteristic size of the regolith grains in the curtain was estimated to be several centimeters. These regolith grains primarily originated from the subsurface layer. We propose three different hypotheses for the geological process that formed the subsurface structure at the SCI impact point consistent with the above observations. Because these hypotheses have different predictions for materials in SCI ejecta, the samples obtained from the second touchdown will be able to constrain which hypothesis is the most likely.

Keywords: Impact phenomena, Asteroids, Planetary science
Destruction of Molecular Hydrogen Ice and Implications for 1I/2017 U1 ('Oumuamua). The first interstellar object observed in our solar system, 1I/2017 U1 ('Oumuamua), exhibited a number of peculiar properties, including extreme elongation and acceleration excess. Recently, Seligman &amp; Laughlin proposed that the object was made out of molecular hydrogen (H2) ice. The question is whether H2 objects could survive their travel from the birth sites to the solar system. Here we study destruction processes of icy H2 objects through their journey from giant molecular clouds (GMCs) to the interstellar medium (ISM) and the solar system, owing to interstellar radiation, gas and dust, and cosmic rays. We find that thermal sublimation due to heating by starlight can destroy 'Oumuamua-size objects in less than 10 Myr. Thermal sublimation by collisional heating in GMCs could destroy H2 objects of 'Oumuamua-size before their escape into the ISM. Most importantly, the formation of icy grains rich in H2 is unlikely to occur in dense environments because collisional heating raises the temperature of the icy grains, so that thermal sublimation rapidly destroys the H2 mantle before grain growth.

Keywords: Amor group, Interstellar dynamics, A stars, Astrosphere interstellar medium interactions, Asteroids, Dense interstellar clouds, Interstellar objects, Comets
The Case for an Early Solar Binary Companion. We show that an equal-mass, temporary binary companion to the Sun in the solar birth cluster at a separation of ∼103 au would have increased the likelihood of forming the observed population of outer Oort Cloud objects and of capturing Planet Nine. In particular, the discovery of a captured origin for Planet Nine would favor our binary model by an order of magnitude relative to a lone stellar history. Our model predicts an overabundance of dwarf planets, discoverable by Legacy Survey of Space and Time, with similar orbits to Planet Nine, which would result from capture by the stellar binary.

Keywords: Oort cloud, Binary stars
Detection Capability of Flux Ropes during the Solar Orbiter Mission. Flux ropes are interplanetary magnetic helical structures that are receiving increasing attention because of their likely role in magnetohydrodynamic (MHD) processes as well as their impact on space weather science. A very promising and powerful approach to address their investigation and characterization is based on wavelet spectrograms of the invariants of the ideal MHD equations. The accuracy of this method to infer flux rope properties depends on the proper evaluation of the direction of propagation of the flux rope itself, which is often difficult to assess. We present a numerical test of the reliability of this diagnostic technique, by simulating a synthetic flux rope of fixed size and propagation direction along the Solar Orbiter orbit, that is very elongated and inclined with respect to the orbital plane. We find that when the flux rope is crossed for less than 50% of its width, the procedure becomes unreliable. Quantitative information on how to properly recover the flux-rope intrinsic properties is provided.

Keywords: Interplanetary medium, Magnetohydrodynamics, Orbiters, Interplanetary turbulence, Astrostatistics techniques, Solar wind, Solar coronal mass ejections, Wavelet analysis, Space vehicles