Sazuna/UAT_keywords huggingface dataset:
Finding Direct-collapse Black Holes at Birth. Direct-collapse black holes (DCBHs) are currently one of the leading contenders for the origins of the first quasars in the universe, over 300 of which have now been found at z &gt; 6. But the birth of a DCBH in an atomically cooling halo does not by itself guarantee it will become a quasar by z ∼ 7, the halo must also be located in cold accretion flows or later merge with a series of other gas-rich halos capable of fueling the BH's rapid growth. Here, we present near-infrared luminosities for DCBHs born in cold accretion flows in which they are destined to grow to 109 ${M}_{\odot }$ by z ∼ 7. Our observables, which are derived from cosmological simulations with radiation hydrodynamics with Enzo, reveal that DCBHs could be found by the James Webb Space Telescope at z ≲ 20 and strongly lensed DCBHs might be found in future wide-field surveys by Euclid and the Wide-Field Infrared Space Telescope at z ≲ 15.

Keywords: Intermediate-mass black holes, Supermassive black holes, Population III stars, Quasars, Primordial galaxies, High-redshift galaxies
On the Dependency between the Peak Velocity of High-speed Solar Wind Streams near Earth and the Area of Their Solar Source Coronal Holes. The relationship between the peak velocities of high-speed solar wind streams near Earth and the areas of their solar source regions, I.e., coronal holes, has been known since the 1970s, but it is still physically not well understood. We perform 3D magnetohydrodynamic (MHD) simulations using the European Heliospheric Forecasting Information Asset (EUHFORIA) code to show that this empirical relationship forms during the propagation phase of high-speed streams from the Sun to Earth. For this purpose, we neglect the acceleration phase of high-speed streams, and project the areas of coronal holes to a sphere at 0.1 au. We then vary only the areas and latitudes of the coronal holes. The velocity, temperature, and density in the cross section of the corresponding high-speed streams at 0.1 au are set to constant, homogeneous values. Finally, we propagate the associated high-speed streams through the inner heliosphere using the EUHFORIA code. The simulated high-speed stream peak velocities at Earth reveal a linear dependence on the area of their source coronal holes. The slopes of the relationship decrease with increasing latitudes of the coronal holes, and the peak velocities saturate at a value of about 730 km s-1, similar to the observations. These findings imply that the empirical relationship between the coronal hole areas and high-speed stream peak velocities does not describe the acceleration phase of high-speed streams, but is a result of the high-speed stream propagation from the Sun to Earth.

Keywords: Solar coronal holes, Solar physics, Magnetohydrodynamics, Fast solar wind
Timing the Early Assembly of the Milky Way with the H3 Survey. The archeological record of stars in the Milky Way opens a uniquely detailed window into the early formation and assembly of galaxies. Here we use 11,000 main-sequence turn-off stars with well-measured ages, $[\mathrm{Fe}/{\rm{H}}]$ , $[\alpha /\mathrm{Fe}]$ , and orbits from the H3 Survey and Gaia to time the major events in the early Galaxy. Located beyond the Galactic plane, $1\lesssim | Z| /\mathrm{kpc}\lesssim 4$ , this sample contains three chemically distinct groups: a low-metallicity population, and low-α and high-α groups at higher metallicity. The age and orbit distributions of these populations show that (1) the high-α group, which includes both disk stars and the in situ halo, has a star formation history independent of eccentricity that abruptly truncated 8.3 ± 0.1 Gyr ago (z ≃ 1); (2) the low-metallicity population, which we identify as the accreted stellar halo, is on eccentric orbits and its star formation truncated $10.2{.}_{-0.1}^{+0.2}$ Gyr ago (z ≃ 2); (3) the low-α population is primarily on low-eccentricity orbits and the bulk of its stars formed less than 8 Gyr ago. These results suggest a scenario in which the Milky Way accreted a satellite galaxy at z ≈ 2 that merged with the early disk by z ≈ 1. This merger truncated star formation in the early high-α disk and perturbed a fraction of that disk onto halo-like orbits. The merger enabled the formation of a chemically distinct, low-α disk at z ≲ 1. The lack of any stars on halo-like orbits at younger ages indicates that this event was the last significant disturbance to the Milky Way disk.

Keywords: Galaxy formation, Stellar ages, Galaxy chemical evolution, Milky Way dynamics, Milky Way stellar halo, Astrometry, Galaxy evolution, Spectroscopy, Milky Way Galaxy
Discovery of a [C I]-faint, CO-bright Galaxy: ALMA Observations of the Merging Galaxy NGC 6052. We report sensitive [C I] 3P1-3P0 and 12CO J = 4-3 observations of the nearby merging galaxy NGC 6052 using the Morita (Atacama Compact) Array of the Atacama Large Millimeter/submillimeter Array (ALMA). We detect 12CO J = 4-3 toward the northern part of NGC 6052, but [C I] 3P1-3P0 is not detected with a [C I] 3P1-3P0 to 12CO J = 4-3 line luminosity ratio of ≲0.07. According to models of photodissociation regions, the unusual weakness of [C I] 3P1-3P0 relative to 12CO J = 4-3 can be explained if the interstellar medium has a hydrogen density larger than ${10}^{5}\,{\mathrm{cm}}^{-3}$ , conditions that might arise naturally in the ongoing merging process in NGC 6052. Its [C I] 3P1-3P0 emission is also weaker than expected given the molecular gas mass inferred from previous measurements of 12CO J = 1-0 and 12CO J = 2-1. This suggests that [C I]3P1-3P0 may not be a reliable tracer of molecular gas mass in this galaxy. NGC 6052 is a unique laboratory to investigate how the merger process impacts the molecular gas distribution.

Keywords: Submillimeter astronomy, Galaxy interactions, Galaxy evolution, Interstellar medium
On Lithium-6 as a Diagnostic of the Lithium-enrichment Mechanism in Red Giants. High lithium-7 (7Li) abundances in giants are indicative of nonstandard physical processes affecting the star. Mechanisms that could produce this signature include contamination from an external source, such as planets, or internal production and subsequent mixing to the stellar surface. However, distinguishing between different families of solutions has proven challenging, and there is no current consensus model that explains all the data. The lithium-6 (6Li) abundance may be a potentially important discriminant, as the relative 6Li and 7Li abundances are expected to be different if the enrichment were to come from internal production or from engulfment. In this work, we model the 6Li and 7Li abundances of different giants after the engulfment of a substellar mass companion. Given that 6Li is more strongly affected by Galactic chemical evolution than 7Li, 6Li is not a good discriminant at low metallicities, where it is expected to be low in both star and planet. For modeled metallicities ([Fe/H] &gt; -0.5), we use a "best-case" initial 6Li/7Li ratio equal to the solar value. 6Li increases significantly after the engulfment of a companion. However, at metallicities close to solar and higher, the 6Li signal does not last long in the stellar surface. As such, detection of surface 6Li in metal-rich red giants would most likely indicate the action of a mechanism for 6Li enrichment other than planet engulfment. At the same time, 6Li should not be used to reject the hypothesis of engulfment in a 7Li-enriched giant or to support a particular 7Li-enhancement mechanism.

Keywords: Stellar evolutionary models, Solar-planetary interactions, Low mass stars, Red giant stars, Lithium stars
The Initiation of a Solar Streamer Blowout Coronal Mass Ejection Arising from the Streamer Flank. Streamer blowout (SBO) coronal mass ejections (CMEs) represent a particular class of CMEs that are characterized by a gradual swelling of the overlying streamer and a slow CME containing a flux-rope structure. SBO CMEs arising from the streamer flank fall into a special category of SBO CMEs involving three lower arches under the higher streamer arcade. However, the initiation mechanism for this special category of SBO CMEs remains elusive, due to the observational limitations. Here we report critical observations of a SBO CME associated with the eruption of a polar crown filament that originated from the streamer flank. The filament slowly rose toward the solar equator with the writhing motion, and underwent a sudden acceleration before its eruption. Interestingly, during the rising, the filament fields experienced gradual external reconnections, which is evidenced by the dip-shaped bottom of the enveloping flux-rope structure changing from a smooth concave, the slow inflows (∼1.8 km s-1) from both the filament fields and the coronal loops beneath, and the persistent brightenings around the interface between the filament fields and the coronal loops beneath. The newly formed lower loops at the filament source and the Y-shaped structure in the stretched tail fields indicate the internal reconnections for the filament eruption. The clear signatures of external and internal reconnections shed light on the initiation mechanisms of SBO CMEs.

Keywords: Solar coronal streamers, Solar coronal mass ejections, Solar magnetic reconnection, Solar filament eruptions
Twin Jets and Close Binary Formation. The formation of a close binary system is investigated using a three-dimensional resistive magnetohydrodynamic simulation. Starting from a prestellar cloud, the cloud evolution is calculated until ∼400 yr after protostar formation. Fragmentation occurs in the gravitationally collapsing cloud, and two fragments evolve into protostars. The protostars orbit each other and a protobinary system appears. A wide-angle low-velocity outflow emerges from the circumbinary streams that enclose two protostars, while each protostar episodically drives high-velocity jets. Thus, the two high-velocity jets are surrounded by the low-velocity circumbinary outflow. The speed of the jets exceeds ≳100 $\mathrm{km}\,{{\rm{s}}}^{-1}$ . Although the jets have a collimated structure, they are swung back on the small scale and are tangled at the large scale due to the binary orbital motion. A circumstellar disk also appears around each protostar. In the early main accretion phase, the binary orbit is complicated, while the binary separation is within &lt;30 au. For the first time, all the characteristics of protobinary systems recently observed with large telescopes are reproduced in a numerical simulation.

Keywords: Jets, Multiple star evolution, Stellar jets, Star formation, Magnetic fields
Differences in Periodic Magnetic Helicity Injection Behavior between Flaring and Non-flaring Active Regions: Case Study. The evolution of magnetic helicity has a close relationship with solar eruptions and is of interest as a predictive diagnostic. In this case study, we analyze the evolution of the normalized emergence, shearing, and total magnetic helicity components in the case of three flaring and three non-flaring active regions (ARs) using Spaceweather Helioseismic Magnetic Imager Active Region Patches vector magnetic field data. The evolution of the three magnetic helicity components is analyzed with wavelet transforms, revealing significant common periodicities of the normalized emergence, shearing, and total helicity fluxes before flares in the flaring ARs. The three non-flaring ARs do not show such common periodic behavior. This case study suggests that the presence of significant periodicities in the power spectrum of magnetic helicity components could serve as a valuable precursor for flares.

Keywords: Solar active region magnetic fields, Solar flares, Space weather, Sunspots, Solar active regions, Solar activity
Manifestation of Rossby Waves in the Global Magnetic Field of the Sun during Cycles 21-24. The evolution of the solar global magnetic field (GMF) was investigated and compared with oscillations of different periods during cycles 21-24. The data from the Wilcox Solar Observatory were used. The results indicate that GMF structures were associated with certain oscillations. Oscillations of 81.83-163.65 days were associated with structures lasting 10-20 CRs. They occurred as some pulses during solar maxima. Oscillations of 163.652-463.680 days were associated with GMF structures lasting ≈20-50 CRs. They match two peaks in the magnetic-field cycle. Oscillations of 1.270-5.231 yr were formed during the dominance of the sectorial GMF structure. Oscillations of 5.231-13.451 yr were the most intense. From cycle 22 to 24, their intensity decreased, and the range of periods narrowed and shifted to longer periods, determining the corresponding changes in the oscillations of 81.83 days-5.231 yr and associated GMF structures. They match well the evolution of the zonal GMF structure. They are assumed to be a descending part of a period of ≈≥60 yr. A decrease in the magnetic field from cycle 22 to 24 may be due to a decrease in the intensity of these oscillations. Some periodicities of the revealed oscillations are in good agreement with the estimates of the periods for fast magnetic Rossby waves. The GMF structure connection with Rossby waves is discussed.

Keywords: Solar cycle, Solar photosphere, Solar magnetic fields, Wavelet analysis, Solar oscillations
Magnetic-buoyancy-induced Mixing in AGB Stars: Presolar SiC Grains. Isotope ratios can be measured in presolar SiC grains from ancient asymptotic giant branch (AGB) stars at permil-level (0.1%) precision. Such precise grain data permit derivation of more stringent constraints and calibrations on mixing efficiency in AGB models than traditional spectroscopic observations. In this paper we compare SiC heavy-element isotope ratios to a new series of FRUITY models that include the effects of mixing triggered by magnetic fields. Based on 2D and 3D simulations available in the literature, we propose a new formulation, upon which the general features of mixing induced by magnetic fields can be derived. The efficiency of such a mixing, on the other hand, relies on physical quantities whose values are poorly constrained. We present here our calibration by comparing our model results with the heavy-element isotope data of presolar SiC grains from AGB stars. We demonstrate that the isotopic compositions of all measured elements (Ni, Sr, Zr, Mo, Ba) can be simultaneously fitted by adopting a single magnetic field configuration in our new FRUITY models.

Keywords: Magnetohydrodynamics, Stellar abundances, Stellar magnetic fields, Asymptotic giant branch stars, Stellar rotation, Circumstellar dust, Chemically peculiar stars
Detection of Periodicity in SiO Maser Intensity and Velocity Shift of the Symbiotic Star CH Cyg. We performed simultaneous monitoring observations of H2O 616-523 and SiO V = 1, 2, $J=1\to $ 0, SiO V = 1, $J=2\to $ 1, $3\to 2$ maser lines toward the symbiotic star CH Cyg from 2012 December to 2019 November using the Korean very long baseline interferometry Network single-dish telescope. SiO V = 1, 2, $J=1\to 0$ and V = 1, $J=2\to 1$ maser lines were detected for the first time. A periodicity of about 2.5 yr in the SiO maser intensity was found, showing its association with the pulsation of the M giant in CH Cyg. Only the SiO V = 2, $J=1\to 0$ maser, without detections of the V = 1, $J=1\to 0$ maser, was detected in 6 epochs out of 15 V = 2, J = 1-0 maser detected epochs. In addition, the SiO V = 1, $J=2\to 1$ maser intensity was always stronger than that of the V = 1, $J=1\to 0$ maser except for one epoch, providing a critical constraint on the different masing conditions by different transitions, according to changes of the CH Cyg symbiotic system. We also found the gradual redshifted peak velocities of the SiO masers had about a 2.5 yr periodicity corresponding to the period of peak intensities (redshifted up to about $+40\,\mathrm{km}\,{{\rm{s}}}^{-1}$ with respect to the stellar velocity of the M giant). Two possible explanations can be suggested for the 2.5 yr period of the SiO maser intensity and velocity behaviors, although their actual causes remain uncertain.

Keywords: Symbiotic binary stars, Silicon monoxide masers, Roche lobe overflow, Circumstellar masers
On the Diversity of M-star Astrospheres and the Role of Galactic Cosmic Rays Within. With upcoming missions such as the James Webb Space Telescope, the European Extremely Large Telescope, and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, we soon will be on the verge of detecting and characterizing Earth-like exoplanetary atmospheres for the first time. These planets are most likely to be found around smaller and cooler K- and M-type stars. However, recent observations showed that their radiation environment might be much harsher than that of the Sun. Thus, the exoplanets are most likely exposed to an enhanced stellar radiation environment, which could affect their habitability, for example, in the form of a hazardous flux of energetic particles. Knowing the stellar radiation field, and being able to model the radiation exposure on the surface of a planet, is crucial to assess its habitability. In this study, we present 3D magnetohydrodynamic-based model efforts investigating M-stars, focusing on V374 Peg, Proxima Centauri, and LHS 1140, chosen because of their diverse astrospheric quantities. We show that V374 Peg has a much larger astrosphere (ASP) than our Sun, while Proxima Centauri and LHS 1140 most likely have ASPs comparable to or even much smaller than the heliosphere, respectively. Based on a 1D transport model, for the first time, we provide numerical estimates of the modulation of Galactic cosmic rays (GCRs) within the three ASPs. We show that the impact of GCRs on the Earth-like exoplanets Proxima Centauri b and LHS 1140 b cannot be neglected in the context of exoplanetary habitability.

Keywords: Magnetohydrodynamics, Stellar wind bubbles, Galactic cosmic rays, Stellar winds, Interstellar medium
Signatures of Intermittency and Fine-scale Turbulence in the Very Local Interstellar Medium. This study presents the first Voyager 1 (V1) observation of magnetic turbulence intermittency and fine-scale structures associated with the propagation of a shock wave in the outer heliosheath. The intermittent event starts on DOY 178 in 2014 upstream of the shock wave that overtook V1 on DOY 237 at 140 au from the Sun. The distribution of magnetic field increments follows the q-Gaussian distribution with the index q ≈ 1.57 for the maximum variance component. Evidence is provided of fine-scale structures well below the Coulomb collisional scale. They undergo a turbulent cascade at scales less than 10-3 au. Observed magnetohydrodynamic fluctuations show signatures of irregular filamentary structures, sawtooth-like waveforms of mixed compressible/transverse nature, which evolve into shocklets and current sheets. Observational data challenges the interpretation of the interstellar plasma in the outer heliosheath as a featureless medium at scales below the collisional mean free path of about 1 au. These results are of importance for better understanding of turbulent processes in the outer heliosheath, including magnetic reconnection, shock-turbulence interaction, Galactic cosmic-ray transport, plasma wave generation, and radio emission.

Keywords: Interstellar magnetic fields, Heliopause, Heliosphere
The Nearest Discovered Black Hole Is Likely Not in a Triple Configuration. HR 6819 was recently claimed to be a hierarchical triple system of a Be star in a wide orbit around an inner binary system of a black hole (BH) and a B III type star. We argue that this system is unlikely to be a hierarchical triple for three reasons. (I) Given that this system is discovered in a magnitude-limited Bright Star Catalog, the expected number of such systems in the Milky Way (MW) amounts to about 104, while the estimate for the MW budget for such systems is between 102 and 103 systems under generous assumptions. Such a large gap cannot be reconciled as it would otherwise likely overflow the MW budget for BHs. (II) The dynamical stability of this system sets lower bounds on the orbital separation of the outer Be star, while it not being resolved by Gaia places an upper limit on its projected sky separation. We show that these two constraints would imply a narrow range for the outer orbit without resorting to geometrical fine-tuning. (III) The triple system should have survived the stellar evolution prior to the formation of the BH in the inner binary. We perform numerical simulations starting with conservative initial conditions of this system and show that a small parameter space for BH progenitor star's mass loss, BH natal kicks, and initial orbital separation can reproduce HR 6819. Therefore, we propose this system is a chance superposition of a Be star with a binary.

Keywords: Orbits, Stellar evolutionary models, Stellar dynamics, Astrophysical black holes
The High Molecular Gas Content, and the Efficient Conversion of Neutral into Molecular Gas, in Jellyfish Galaxies. In the disks of four jellyfish galaxies from the GASP sample at redshift ∼0.05 we detect molecular gas masses systematically higher than in field galaxies. These galaxies are being stripped of their gas by ram pressure from the intracluster medium and are, in general, forming stars at a high rate with respect to nonstripped galaxies of similar stellar masses. We find that, unless giant molecular clouds in the disk are unbound by ram pressure leading to exceptionally high CO-to-H2 conversion factors, these galaxies have a molecular gas content 4-5 times higher than normal galaxies of similar masses, and molecular gas depletion times ranging from ∼1 to 9 Gyr, corresponding to generally very low star formation efficiencies. The molecular gas mass within the disk is a factor between 4 and ∼100 times higher than the neutral gas mass, as opposed to the disks of normal spirals that contain similar amounts of molecular and neutral gas. Intriguingly, the molecular plus neutral total amount of gas is similar to that in normal spiral galaxies of similar stellar mass. These results strongly suggest that ram pressure in disks of galaxies during the jellyfish phase leads to a very efficient conversion of H I into H2.

Keywords: Galaxy clusters, Molecular gas, Disk galaxies
Optical Detection of the 1.1 day Variability at the White Dwarf GD 394 with TESS. Recent discoveries have demonstrated that planetary systems routinely survive the post-main-sequence evolution of their host stars, leaving the resulting white dwarf with a rich circumstellar environment. Among the most intriguing of such hosts is the hot white dwarf GD 394, exhibiting a unique 1.150 ± 0.003 day flux variation detected in Extreme Ultraviolet Explorer (EUVE) observations in the mid-1990s. The variation has eluded a satisfactory explanation, but hypotheses include channeled accretion producing a dark spot of metals, occultation by a gas cloud from an evaporating planet, or heating from a flux tube produced by an orbiting iron-cored planetesimal. We present observations obtained with the Transiting Exoplanet Survey Satellite (TESS) of GD 394. The space-based optical photometry demonstrates a 0.12 ± 0.01% flux variation with a period of 1.146 ± 0.001 days, consistent with the EUVE period and the first re-detection of the flux variation outside of the extreme ultraviolet. We describe the analysis of the TESS light curve and measurement of the optical variation, and discuss the implications of our results for the various physical explanations put forward for the variability of GD 394.

Keywords: Exoplanets, White dwarf stars, Variable stars