Sazuna/UAT_keywords huggingface dataset:
Star Formation Activity beyond the Outer Arm. II. Distribution and Properties of Star Formation. The outer Galaxy beyond the Outer Arm represents a promising opportunity to study star formation in an environment vastly different from the solar neighborhood. In our previous study, we identified 788 candidate star-forming regions in the outer Galaxy (at galactocentric radii R G ≥ 13.5 kpc) based on the Wide-field Infrared Survey Explorer (WISE) mid-infrared (MIR) all-sky survey. In this paper, we investigate the statistical properties of the candidates and their parental molecular clouds derived from the Five College Radio Astronomy Observatory (FCRAO) CO survey. We show that the molecular clouds with candidates have cloud mass functions with shallower slopes, larger fractions of clouds bound by self-gravity, and a greater density than the molecular clouds without candidates. To investigate the star formation efficiency (SFE) at different R G, we used two parameters: (1) the fraction of molecular clouds with candidates and (2) the monochromatic MIR luminosities of candidates per parental molecular cloud mass. We did not find any clear correlation between SFE parameters and R G at R G of 13.5-20.0 kpc, suggesting that the SFE is independent of environmental parameters such as metallicity and gas surface density, which vary considerably with R G. Previous studies reported that the SFE per year (SFE/yr) derived from the star formation rate surface density per total gas surface density, H I plus H2, decreases with increased R G. Our results might suggest that the decreasing trend is due to a decrease in the conversion of H I gas to H2 gas.

Keywords: Milky Way Galaxy, Star formation, Molecular clouds, Interstellar medium
Black Hole Hyperaccretion in Collapsars. III. GRB Timescale. Gamma-ray bursts (GRBs) are classified into long and short populations (i.e., LGRBs and SGRBs) based on the observed bimodal distribution of duration T 90. Multimessenger observations indicate that most SGRBs and LGRBs should be powered by ultrarelativistic jets launched from black hole (BH) hyperaccretion in compact-object mergers and massive collapsars, respectively. However, the duration criterion sometimes cannot correctly reflect the physical origin of a particular GRB. In the collapsar scenario, a GRB can be observed when the jet breaks out from the envelope and circumstellar medium successfully. The observed GRB duration reflects only the time the engine operates after the jet breaks out. This work studies the propagation of jets driven by the neutrino annihilation or Blandford-Znajek mechanism in massive collapsars. The signatures of the progenitors producing LGRBs, SGRBs, and failed GRBs in the collapsar scenario are exhibited. The competition between the mass supply onto the BH hyperaccretion and jet propagation into the envelope is definitely dependent on the density profiles of the collapsars. We show that duration and isotropic energy E  γ,iso of GRBs can help constrain the density profiles of collapsars. Finally, we propose that a collapsar-origin SGRB, GRB 200826A, might originate from a neutrino-annihilation-dominated jet launched by a ~10 M ⊙ collapsar whose progenitor's envelope has been stripped.

Keywords: Accretion, Relativistic jets, Black holes, Gamma-ray bursts
Slow Diffusion is Necessary to Explain the γ-Ray Pulsar Halos. It was suggested that the γ-ray halo around Geminga might not be interpreted by slow diffusion. If the ballistic regime of electron/positron propagation is considered, the Geminga halo may be explained even with a large diffusion coefficient. In this work, we examine this effect by taking the generalized Jüttner propagator as the approximate relativistic Green's function for diffusion and find that the morphology of the Geminga halo can be marginally fitted in the fast-diffusion scenario. However, the recently discovered γ-ray halo around PSR J0622+3749 at the Large High-Altitude Air Shower Observatory cannot be explained by the same effect and slow diffusion is the only solution. Furthermore, both the two pulsar halos require a conversion efficiency from the pulsar spin-down energy to the high-energy electrons/positrons much larger than 100%, if they are interpreted by this ballistic transport effect. Therefore, we conclude that slow diffusion is necessary to account for the γ-ray halos around pulsars.

Keywords: Gamma-ray astronomy, Cosmic rays
Ultrawide Black Hole-Neutron Star Binaries as a Possible Source for Gravitational Waves and Short Gamma-Ray Bursts. The third observing run of the LIGO/Virgo/KARGA collaboration reported a few neutron star-black hole (NSBH) merger events. While NSBH mergers have yet to receive extensive theoretical attention, they may have a promising electromagnetic signature in the form of short gamma-ray bursts. Here we show that NSBH dynamical mergers can naturally form from ultrawide binaries in the field. Flyby gravitational interactions with other neighbors in the galaxy in these ultrawide systems may result in high eccentricity that drives the binary into a merger. We show that this process can result in a merger rate at the order of ~10 Gpc-3 yr-1 (~1 Gpc-3 yr-1) for elliptical (spiral) galaxies. This channel predicts a higher merger rate with a higher velocity dispersion of the host galaxy, a delay time distribution that is steeper than uniform but shallower than 1/t, and a higher merger rate for a lower black hole to neutron star mass ratio.

Keywords: Neutron stars, Gamma-ray bursts, Stellar mass black holes, Gravitational wave sources, Celestial mechanics
The Long Stare at Hercules X-1. I. Emission Lines from the Outer Disk, the Magnetosphere Boundary, and the Accretion Curtain. Hercules X-1 is a nearly edge-on accreting X-ray pulsar with a warped accretion disk, precessing with a period of about 35 days. The disk precession allows for unique and changing sightlines toward the X-ray source. To investigate the accretion flow at a variety of sightlines, we obtained a large observational campaign on Her X-1 with XMM-Newton (380 ks exposure) and Chandra (50 ks exposure) for a significant fraction of a single disk precession cycle, resulting in one of the best data sets taken to date on a neutron star X-ray binary. Here we present the spectral analysis of the high state high-resolution grating and CCD data sets, including the extensive archival data available for this famous system. The observations reveal a complex Fe K region structure, with three emission line components of different velocity widths. Similarly, the high-resolution soft X-ray spectra reveal a number of emission lines of various widths. We correct for the uncertain gain of the European Photon Imaging Camera pn Timing mode spectra, and track the evolution of these spectral components with Her X-1 precession phase and observed luminosity. We find evidence for three groups of emission lines, the first of which originates in the outer accretion disk (105 R G from the neutron star). The second line group plausibly originates at the boundary between the inner disk and the pulsar magnetosphere (103 R G). The last group is too broad to arise in the magnetically truncated disk and instead must originate very close to the neutron star surface, likely from X-ray reflection from the accretion curtain (~102 R G).

Keywords: Accretion, Neutron stars, X-ray binary stars
Evidence for an Interaction between the Galactic Center Clouds M0.10-0.08 and M0.11-0.11. We present high-resolution (~2-3″; ~0.1 pc) radio observations of the Galactic center cloud M0.10-0.08 using the Very Large Array at K and Ka band (~25 and 36 GHz). The M0.10-0.08 cloud is located in a complex environment near the Galactic center Radio Arc and the adjacent M0.11-0.11 molecular cloud. From our data, M0.10-0.08 appears to be a compact molecular cloud (~3 pc) that contains multiple compact molecular cores (5+; &lt;0.4 pc). In this study, we detect a total of 15 molecular transitions in M0.10-0.08 from the following molecules: NH3, HC3N, CH3OH, HC5N, CH3CN, and OCS. We have identified more than sixty 36 GHz CH3OH masers in M0.10-0.08 with brightness temperatures above 400 K and 31 maser candidates with temperatures between 100 and 400 K. We conduct a kinematic analysis of the gas using NH3 and detect multiple velocity components toward this region of the Galactic center. The bulk of the gas in this region has a velocity of 51.5 km s-1 (M0.10-0.08) with a lower-velocity wing at 37.6 km s-1. We also detect a relatively faint velocity component at 10.6 km s-1 that we attribute to being an extension of the M0.11-0.11 cloud. Analysis of the gas kinematics, combined with past X-ray fluorescence observations, suggests M0.10-0.08 and M0.11-0.11 are located in the same vicinity of the Galactic center and could be physically interacting.

Keywords: Galactic center, Molecular clouds, Interstellar medium
Kepler and TESS Observations of PG 1159-035. PG 1159-035 is the prototype of the PG 1159 hot (pre-)white dwarf pulsators. This important object was observed during the Kepler satellite K2 mission for 69 days in 59 s cadence mode and by the TESS satellite for 25 days in 20 s cadence mode. We present a detailed asteroseismic analysis of those data. We identify a total of 107 frequencies representing 32 ℓ = 1 modes, 27 frequencies representing 12 ℓ = 2 modes, and eight combination frequencies. The combination frequencies and the modes with very high k values represent new detections. The multiplet structure reveals an average splitting of 4.0 ± 0.4 μHz for ℓ = 1 and 6.8 ± 0.2 μHz for ℓ = 2, indicating a rotation period of 1.4 ± 0.1 days in the region of period formation. In the Fourier transform of the light curve, we find a significant peak at 8.904 ± 0.003 μHz suggesting a surface rotation period of 1.299 ± 0.002 days. We also present evidence that the observed periods change on timescales shorter than those predicted by current evolutionary models. Our asteroseismic analysis finds an average period spacing for ℓ = 1 of 21.28 ± 0.02 s. The ℓ = 2 modes have a mean spacing of 12.97 ± 0.4 s. We performed a detailed asteroseismic fit by comparing the observed periods with those of evolutionary models. The best-fit model has T eff = 129, 600 ± 11 100 K, M * = 0.565 ± 0.024M ⊙, and $\mathrm{log}g={7.41}_{-0.54}^{+0.38}$ , within the uncertainties of the spectroscopic determinations. We argue for future improvements in the current models, e.g., on the overshooting in the He-burning stage, as the best-fit model does not predict excitation for all of the pulsations detected in PG 1159-035.

Keywords: White dwarf stars, Asteroseismology, Pulsating variable stars
The Molecular Composition of Shadowed Proto-solar Disk Midplanes Beyond the Water Snowline. The disk midplane temperature is potentially affected by the dust traps/rings. The dust depletion beyond the water snowline will cast a shadow. In this study, we adopt a detailed gas-grain chemical reaction network, and investigate the radial gas and ice abundance distributions of dominant carbon-, oxygen-, and nitrogen-bearing molecules in disks with shadow structures beyond the water snowline around a proto-solar-like star. In shadowed disks, the dust grains at r ~ 3-8 au are predicted to have more than ~5-10 times the amount of ices of organic molecules such as H2CO, CH3OH, and NH2CHO, saturated hydrocarbon ices such as CH4 and C2H6, in addition to H2O, CO, CO2, NH3, N2, and HCN ices, compared with those in non-shadowed disks. In the shadowed regions, we find that hydrogenation (especially of CO ice) is the dominant formation mechanism of complex organic molecules. The gas-phase N/O ratios show much larger spatial variations than the gas-phase C/O ratios; thus, the N/O ratio is predicted to be a useful tracer of the shadowed region. N2H+ line emission is a potential tracer of the shadowed region. We conclude that a shadowed region allows for the recondensation of key volatiles onto dust grains, provides a region of chemical enrichment of ices that is much closer to the star than within a non-shadowed disk, and may explain to some degree the trapping of O2 ice in dust grains that formed comet 67P/Churyumov-Gerasimenko. We discuss that, if formed in a shadowed disk, Jupiter does not need to have migrated vast distances.

Keywords: Interstellar molecules, Exoplanet atmospheres, Interstellar abundances, Planetary atmospheres, Astrochemistry, Planetary system formation, Protoplanetary disks, Planet formation
Testing Lyα Emission-line Reconstruction Routines at Multiple Velocities in One System. The 1215.67 Å H I Lyα emission line dominates the ultraviolet flux of low-mass stars, including the majority of known exoplanet hosts. Unfortunately, strong attenuation by the interstellar medium (ISM) obscures the line core in most stars, requiring the intrinsic Lyα flux to be reconstructed based on fits to the line wings. We present a test of the widely used Lyα emission-line reconstruction code LYAPY using phase-resolved, medium-resolution STIS G140M observations of the close white dwarf-M dwarf binary EG UMa. The Doppler shifts induced by the binary orbital motion move the Lyα emission line in and out of the region of strong ISM attenuation. Reconstructions of each spectrum should produce the same Lyα profile regardless of phase, under the well-justified assumption that there is no intrinsic line variability between observations. Instead, we find that the reconstructions underestimate the Lyα flux by almost a factor of 2 for the lowest velocity, most attenuated spectrum, due to a degeneracy between the intrinsic Lyα and ISM profiles. Our results imply that many stellar Lyα fluxes derived from G140M spectra reported in the literature may be underestimated, with potential consequences for, for example, estimates of extreme-ultraviolet stellar spectra and ultraviolet inputs into simulations of exoplanet atmospheres.

Keywords: M dwarf stars, White dwarf stars, Ultraviolet astronomy, Planet hosting stars, Common envelope binary stars
GRB 190829A-A Showcase of Binary Late Evolution. GRB 190829A is the fourth-closest gamma-ray burst to date (z = 0.0785). Owing to its wide range of radio, optical, X-ray, and very-high-energy observations by HESS, it has become an essential new source that has been examined by various models with complementary approaches. Here, we show in GRB 190829A that the double prompt pulses and the three multiwavelength afterglows are consistent with the type II binary-driven hypernova model. The progenitor is a binary composed of a carbon-oxygen (CO) star and a neutron star (NS) companion. The gravitational collapse of the iron core of the CO star produces a supernova (SN) explosion and leaves behind a new NS (νNS) at its center. The accretion of the SN ejecta onto the NS companion and onto the νNS via matter fallback spins up the NSs and produces the double-peak prompt emission. The synchrotron emission from the expanding SN ejecta, with energy injection from the rapidly spinning νNS and its subsequent spindown, leads to the afterglow in the radio, optical, and X-ray bands. We model the sequence of physical and related radiation processes in BdHNe, and focus on individuating the binary properties that play the relevant roles.

Keywords: Neutron stars, Black hole physics, Type Ic supernovae, Gamma-ray bursts, Supernovae
ALMA Detection of Parsec-scale Blobs at the Head of a Kiloparsec-scale Jet in the Nearby Seyfert Galaxy NGC 1068. We present Atacama Large Millimeter/submillimeter Array observations at ≍100 GHz with 0.″05 (3 pc) resolution of the kiloparsec-scale jet seen in the nearby Seyfert galaxy NGC 1068, and we report the presence of parsec-scale blobs at the head of the jet. The combination of the detected radio flux (≍0.8 mJy), spectral index (≍0.5), and blob size (≍10 pc) suggests a strong magnetic field of B ≍ 240 μG. Such a strong magnetic field most likely implies magnetic field amplification by streaming cosmic rays. The estimated cosmic-ray power of the jet may exceed the limit set by the star formation activity in this galaxy. This result suggests that even modest-power jets can increase the galactic cosmic-ray content while propagating through the galactic bulge.

Keywords: Cosmic ray astronomy, Active galactic nuclei, Galaxy jets, High energy astrophysics
The Unmixed Debris of Gaia-Sausage/Enceladus in the Form of a Pair of Halo Stellar Overdensities. In the first billion years after its formation, the Galaxy underwent several mergers with dwarf satellites of various masses. The debris of Gaia-Sausage/Enceladus (GSE), the galaxy responsible for the last significant merger of the Milky Way, dominates the inner halo and has been suggested to be the progenitor of both the Hercules-Aquila Cloud (HAC) and Virgo Overdensity (VOD). We combine SEGUE, APOGEE, Gaia, and StarHorse distances to characterize the chemodynamical properties and verify the link between HAC, VOD, and GSE. We find that the orbital eccentricity distributions of the stellar overdensities and GSE are comparable. We also find that they have similar, strongly peaked, metallicity distribution functions, reinforcing the hypothesis of common origin. Furthermore, we show that HAC and VOD are indistinguishable from the prototypical GSE population within all chemical-abundance spaces analyzed. All these evidences combined provide a clear demonstration that the GSE merger is the main progenitor of the stellar populations found within these halo overdensities.

Keywords: Milky Way formation, Galactic archaeology, Milky Way dynamics, Milky Way stellar halo, Milky Way evolution
Antaeus: A Retrograde Group of Tidal Debris in the Milky Way's Disk Plane. We present the discovery of a wide retrograde moving group in the disk plane of the Milky Way using action-angle coordinates derived from the Gaia DR3 catalog. The structure is identified from a sample of its members that are currently almost at the pericenter of their orbit and are passing through the solar neighborhood. The motions of the stars in this group are highly correlated, indicating that the system is probably not phase mixed. With a width of at least 1.5 kpc and with a probable intrinsic spread in metallicity, this structure is most likely the wide remnant of a tidal stream of a disrupted ancient dwarf galaxy (age ~12 Gyr, &lt;[Fe/H]&gt; ~ -1.74). The structure presents many similarities (e.g., in energy, angular momentum, metallicity, and eccentricity) with the Sequoia merging event. However, it possesses extremely low vertical action J  z  , which makes it unique even among Sequoia dynamical groups. As the low J  z  may be attributable to dynamical friction, we speculate that these stars may be the remnants of the dense core of the Sequoia progenitor.

Keywords: Local Group, Stellar streams, Tidal disruption, Milky Way dynamics, Milky Way disk, Milky Way stellar halo, Galaxies
The Origin of the Doppler Flip in HD 100546: A Large-scale Spiral Arm Generated by an Inner Binary Companion. Companions at subarcsecond separation from young stars are difficult to image. However, their presence can be inferred from the perturbations they create in the dust and gas of protoplanetary disks. Here we present a new interpretation of SPHERE polarized observations that reveal the previously detected inner spiral in the disk of HD 100546. The spiral coincides with a newly detected 12CO inner spiral and the previously reported CO emission Doppler flip, which has been interpreted as the signature of an embedded protoplanet. Comparisons with hydrodynamical models indicate that this Doppler flip is instead the kinematic counterpart of the spiral, which is likely generated by an inner companion inside the disk cavity.

Keywords: Protoplanetary disks
Bridging the Bondi and Event Horizon Scales: 3D GRMHD Simulations Reveal X-shaped Radio Galaxy Morphology. X-shaped radio galaxies (XRGs) produce misaligned X-shaped jet pairs and make up ≲10% of radio galaxies. XRGs are thought to emerge in galaxies featuring a binary supermassive black hole (SMBH), SMBH merger, or large-scale ambient medium asymmetry. We demonstrate that XRG morphology can naturally form without such special, preexisting conditions. Our 3D general-relativistic magnetohydrodynamic (GRMHD) simulation for the first time follows magnetized rotating gas from outside the SMBH sphere of influence of radius R B to the SMBH of gravitational radius R g at the largest scale separation, R B/R g = 103, to date. Initially, our axisymmetric system of constant-density hot gas contains a weak vertical magnetic field and rotates in the equatorial plane of a rapidly spinning SMBH. We seed the gas with small-scale 2% level pressure perturbations. Infalling gas forms an accretion disk, and the SMBH launches relativistically magnetized collimated jets reaching well outside R B. Under the pressure of the infalling gas, the jets intermittently turn on and off, erratically wobble, and inflate pairs of cavities in different directions, resembling an X-shaped jet morphology. Synthetic X-ray images reveal multiple pairs of jet-powered shocks and cavities. Large-scale magnetic flux accumulates on the SMBH, becomes dynamically important, and leads to a magnetically arrested disk state. The SMBH accretes at 2% of the Bondi rate ( $\dot{M}\simeq 2.4\times {10}^{-3}{M}_{\odot }\,{\mathrm{yr}}^{-1}$ for M87*) and launches twin jets at η = 150% efficiency. These jets are powerful enough (P jets ≃ 2 × 1044 erg s-1) to escape along the SMBH spin axis and end the short-lived intermittent jet state, whose transient nature can account for the rarity of XRGs.

Keywords: Black hole physics, Jets, High energy astrophysics, Active galactic nuclei, General relativity, Magnetohydrodynamical simulations
The First Detection of a Protostellar CO Outflow in the Small Magellanic Cloud with ALMA. Protostellar outflows are one of the most outstanding features of star formation. Observational studies over the last several decades have successfully demonstrated that outflows are ubiquitously associated with low- and high-mass protostars in solar-metallicity Galactic conditions. However, the environmental dependence of protostellar outflow properties is still poorly understood, particularly in the low-metallicity regime. Here we report the first detection of a molecular outflow in the Small Magellanic Cloud with 0.2 Z ⊙, using Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.1 pc toward the massive protostar Y246. The bipolar outflow is nicely illustrated by high-velocity wings of CO(3-2) emission at ≳15 km s-1. The evaluated properties of the outflow (momentum, mechanical force, etc.) are consistent with those of the Galactic counterparts. Our results suggest that the molecular outflows, i.e., the guidepost of the disk accretion at the small scale, might be universally associated with protostars across the metallicity range of ~0.2-1 Z ⊙.

Keywords: Local Group, Small Magellanic Cloud, Molecular clouds, Star formation, Interstellar medium, Protostars
Evidence for Corotation Origin of Super-metal-rich Stars in LAMOST-Gaia: Multiple Ridges with a Similar Slope in the ϕ versus L <SUB>z</SUB> Plane. Super-metal-rich (SMR) stars in the solar neighborhood are thought to be born in the inner disk and come to their present location by radial migration, which is most intense at the corotation resonance (CR) of the Galactic bar. In this work, we show evidence for the CR origin of SMR stars in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and Gaia by detecting six ridges and undulations in the ϕ versus L z space coded by median V R, following a similar slope of -8 km s-1 kpc deg-1. The slope is predicted by Monario et al.'s model for CR of a large and slow Galactic bar. For the first time, we show the variation in the angular momentum with azimuths from -10° to 20° for two outer and broad undulations with negative V R around - 18 km s-1 following this slope. The wave-like pattern with large amplitude outside CR and a wide peak of the second undulation indicate that minor merger of the Sagittarius dwarf galaxy with the disk might play a role besides the significant impact of the CR of the Galactic bar.

Keywords: Galaxy disks, Galaxy evolution, Stellar kinematics