Sazuna/UAT_keywords huggingface dataset:
A Comprehensive X-Ray Report on AT2019wey. Here, we present MAXI, Swift, NICER, NuSTAR, and Chandra observations of the X-ray transient AT2019wey (SRGA J043520.9+552226, SRGE J043523.3+552234). From spectral and timing analyses we classify it as a Galactic low-mass X-ray binary (LMXB) with a black hole (BH) or neutron star (NS) accretor. AT2019wey stayed in the low/hard state (LHS) from 2019 December to 2020 August 21, and the hard-intermediate state (HIMS) from 2020 August 21 to 2020 November. For the first six months of the LHS, AT2019wey had a flux of ~1 mCrab, and displayed a power-law X-ray spectrum with photon index Γ = 1.8. From 2020 June to August, it brightened to ~20 mCrab. Spectral features characteristic of relativistic reflection became prominent. On 2020 August 21, the source left the "hard line" on the rms-intensity diagram, and transitioned from LHS to HIMS. The thermal disk component became comparable to the power-law component. A low-frequency quasi-periodic oscillation (QPO) was observed. The QPO central frequency increased as the spectrum softened. No evidence of pulsation was detected. We are not able to decisively determine the nature of the accretor (BH or NS). However, the BH option is favored by the position of this source on the Γ-LX, Lradio-LX, and Lopt-LX diagrams. We find the BH candidate XTE J1752-223 to be an analog of AT2019wey. Both systems display outbursts with long plateau phases in the hard states. We conclude by noting the potential of SRG in finding new members of this emerging class of low luminosity and long-duration LMXB outbursts.

Keywords: Accretion, X-ray binary stars, Black holes, Transient sources, X-ray transient sources, X-ray sources, Low-mass x-ray binary stars
Detection of Lyman Continuum from 3.0 &lt; z &lt; 3.5 Galaxies in the HETDEX Survey. Questions as to what drove the bulk reionization of the universe, how that reionization proceeded, and how the hard ionizing radiation reached the intergalactic medium remain open and debated. Observations probing that epoch are severely hampered by the increasing amounts of neutral gas with increasing redshift, so a small, but growing, number of experiments are targeting star-forming galaxies (z ~ 3) as proxies. However, these studies, while providing fantastic detail, are time intensive, contain relatively few targets, and can suffer from selection biases. As a complementary alternative, we investigate whether stacking the already vast (and growing) numbers of low-resolution (Δλ/λ = 800) Lyα-emitting (LAE) galaxy spectra from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) can be used to measure ionizing photons (rest-frame 880-910 Å) escaping their galaxy hosts. As a blind survey, HETDEX avoids the biases from continuum-selected galaxies, and its planned 540 deg2 coverage promotes the statistical power of large numbers. In this paper, we confirm the feasibility of Lyman continuum detection by carefully selecting a sample of 214 high-redshift (z ~ 3) LAEs from a subset of HETDEX observations, stacking their spectra and measuring a ≳3σ detection of 0.10 μJy rest-frame Lyman continuum emission, uncorrected for attenuation in the intergalactic medium, over the full sample stack (3.0 &lt; z &lt; 3.5 and -22.0 ≲ MUV ≲ -19.0).

Keywords: Lyman-alpha galaxies, Reionization
Comparative Analysis of the 2020 November 29 Solar Energetic Particle Event Observed by Parker Solar Probe. We analyze two specific features of the intense solar energetic particle (SEP) event observed by Parker Solar Probe (PSP) between 2020 November 29 and 2020 December 2. The interplanetary counterpart of the coronal mass ejection (CME) on 2020 November 29 that generated the SEP event (hereafter ICME-2) arrived at PSP (located at 0.8 au from the Sun) on 2020 December 1. ICME-2 was preceded by the passage of an interplanetary shock at 18:35 UT on 2020 November 30 (hereafter S2), that in turn was preceded by another ICME (i.e., ICME-1) observed in situ on 2020 November 30. The two interesting features of this SEP event at PSP are the following: First, the presence of the intervening ICME-1 affected the evolution of the ≲8 MeV proton intensity-time profiles resulting in the observation of inverted energy spectra throughout the passage of ICME-1. Second, the sheath region preceding ICME-2 was characterized by weak magnetic fields compared to those measured immediately after the passage of the shock S2 and during the passage of ICME-2. Comparison with prior SEP events measured at 1 au but with similar characteristics indicates that (1) low-energy particles accelerated by S2 were excluded from propagating throughout ICME-1, and (2) the low magnetic fields measured in the sheath of ICME-2 resulted from the properties of the upstream solar wind encountered by ICME-2 that was propagated into the sheath, whereas the energy density of the high-energy particles in the sheath did not play a dominant role in the formation of these low magnetic fields.

Keywords: Solar energetic particles, Interplanetary shocks, Interplanetary magnetic fields, Solar coronal mass ejections
Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs. Super-puffs-low-mass exoplanets with extremely low bulk density-are attractive targets for exploring their atmospheres and formation processes. Recent studies suggested that the large radii of super-puffs may be caused by atmospheric dust entrained in the escaping atmospheres. In this study, we investigate how the dust grows in escaping atmospheres and influences the transit radii using a microphysical model of grain growth. Collision growth is efficient in many cases, hindering the upward transport of dust via enhanced gravitational settling. We find that the dust abundance in the outflow hardly exceeds the Mach number at the dust production region. Thus, dust formed in the upper atmospheres, say at P ≲ 10-5 bar, is needed to launch a dusty outflow with a high dust abundance. With sufficiently high dust production altitudes and rates, the dusty outflow can enhance the observable radius by a factor of ~2 or even more. We suggest that photochemical haze is a promising candidate of high-altitude dust that can be entrained in the outflow. We also compute the synthetic transmission spectra of super-puff atmospheres and demonstrate that the dusty outflow produces a broad spectral slope and obscures molecular features, in agreement with featureless spectra recently reported for several super-puffs. Lastly, using an interior structure model, we suggest that the atmospheric dust could drastically enhance the observable radius only for planets in a narrow mass range of ~2-5 M⊕, in which the boil-off tends to cause total atmospheric loss. This may explain why super-puffs are uncommon despite the suggested universality of photochemical hazes.

Keywords: Atmospheric clouds, Exoplanet rings, Exoplanet atmospheres, Transmission spectroscopy
High-frequency Wave Power Observed in the Solar Chromosphere with IBIS and ALMA. We present observational constraints on the chromospheric heating contribution from acoustic waves with frequencies between 5 and 50 mHz. We use observations from the Dunn Solar Telescope in New Mexico, complemented with observations from the Atacama Large Millimeter Array collected on 2017 April 23. The properties of the power spectra of the various quantities are derived from the spectral lines of Ca II 854.2 nm, H I 656.3 nm, and the millimeter continuum at 1.25 and 3 mm. At the observed frequencies, the diagnostics almost all show a power-law behavior, whose particulars (slope, peak, and white-noise floors) are correlated with the type of solar feature (internetwork, network, and plage). In order to disentangle the vertical versus transverse Alfvénic plasma motions, we examine two different fields of view: one near disk center, and the other close to the limb. To infer the acoustic flux in the middle chromosphere, we compare our observations with synthetic observables from the time-dependent radiative hydrodynamic RADYN code. Our findings show that acoustic waves carry up to about 1 kW m-2 of energy flux in the middle chromosphere, which is not enough to maintain the quiet chromosphere. This is in contrast to previous publications.

Keywords: Solar atmosphere, Radiative transfer, Spectroscopy
Which Molecular Cloud Structures Are Bound?. We analyze surveys of molecular cloud structures defined by tracers ranging from CO J = 1 → 0 through 13CO J = 1 → 0 to dust emission together with NH3 data. The mean value of the virial parameter and the fraction of mass in bound structures depends on the method used to identify structures. Generally, the virial parameter decreases and the fraction of mass in bound structures increases with the effective density of the tracer, the surface density and mass of the structures, and the distance from the center of a galaxy. For the most complete surveys of structures in the Galaxy defined by CO J = 1 → 0, the fraction of mass that is in bound structures is 0.19. For catalogs of other galaxies based on CO J = 2 → 1, the fraction is 0.35. These results offer substantial alleviation of the fundamental problem of slow star formation. If only clouds found to be bound are counted and they are assumed to collapse in a freefall time at their mean cloud density, the sum over all clouds in a complete survey of the Galaxy yields a predicted star formation rate of 46 M⊙ yr-1, a factor of 6.5 less than if all clouds are bound.

Keywords: Star forming regions, Molecular clouds
AT 2019qyl in NGC 300: Internal Collisions in the Early Outflow from a Very Fast Nova in a Symbiotic Binary. Nova eruptions, thermonuclear explosions on the surfaces of white dwarfs (WDs), are now recognized to be among the most common shock-powered astrophysical transients. We present the early discovery and rapid ultraviolet (UV), optical, and infrared (IR) temporal development of AT 2019qyl, a recent nova in the nearby Sculptor Group galaxy NGC 300. The light curve shows a rapid rise lasting ≲1 day, reaching a peak absolute magnitude of MV = -9.2 mag and a very fast decline, fading by 2 mag over 3.5 days. A steep dropoff in the light curves after 71 days and the rapid decline timescale suggest a low-mass ejection from a massive WD with MWD ≳ 1.2 M☉. We present an unprecedented view of the early spectroscopic evolution of such an event. Three spectra prior to the peak reveal a complex, multicomponent outflow giving rise to internal collisions and shocks in the ejecta of an He/N-class nova. We identify a coincident IR-variable counterpart in the extensive preeruption coverage of the transient location and infer the presence of a symbiotic progenitor system with an O-rich asymptotic-giant-branch donor star, as well as evidence for an earlier UV-bright outburst in 2014. We suggest that AT 2019qyl is analogous to the subset of Galactic recurrent novae with red-giant companions such as RS Oph and other embedded nova systems like V407 Cyg. Our observations provide new evidence that internal shocks between multiple, distinct outflow components likely contribute to the generation of the shock-powered emission from such systems. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. † Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: White dwarf stars, Novae, Asymptotic giant branch stars, Recurrent novae, Spectroscopy, Symbiotic binary stars
Breaching the Limit: Formation of GW190521-like and IMBH Mergers in Young Massive Clusters. The LIGO-Virgo-Kagra Collaboration (LVC) discovered recently GW190521, a gravitational wave (GW) source associated with the merger between two black holes (BHs) with mass 66 and &gt;85 M⊙. GW190521 represents the first BH binary merger with a primary mass falling in the upper-mass gap and the first leaving behind an ~150 M⊙ remnant. So far, the LVC has reported the discovery of four further mergers having a total mass &gt;100 M⊙, i.e., in the intermediate-mass black hole (IMBH) mass range. Here, we discuss results from a series of 80 N-body simulations of young massive clusters that implement relativistic corrections to follow compact object mergers. We discover the development of a GW190521-like system as the result of a third-generation merger, and four IMBH-BH mergers with total mass (300-350)M⊙. We show that these IMBH-BH mergers are low-frequency GW sources detectable with LISA and Deci-hertz Interferometer Gravitational wave Observatory (DECIGO) out to redshift z = 0.01-0.1 and z &gt; 100, and we discuss how their detection could help unraveling IMBH natal spins. For the GW190521 test case, we show that the third-generation merger remnant has a spin and effective spin parameter that matches the 90% credible interval measured for GW190521 better than a simpler double merger and comparable to a single merger. Due to GW recoil kicks, we show that retaining the products of these mergers require birth sites with escape velocities ≳50-100 km s-1, values typically attained in galactic nuclei and massive clusters with steep density profiles.

Keywords: Globular star clusters, Intermediate-mass black holes, Gravitational wave detectors, Black holes, Young star clusters, Stellar mass black holes, Gravitational wave sources, Galaxy nuclei, Gravitational wave astronomy, Astrophysical black holes
Integrated Photometry of Multiple Stellar Populations in Globular Clusters. Evidence that multiple populations (MPs) are common properties of globular clusters (GCs) has accumulated over the past decades from clusters in the Milky Way and in its satellites. This finding has revived research into GCs, and suggested that their formation at high redshift must have been a much more complex phenomenon than imagined before. However, most information on MPs is limited to nearby GCs. The main limitation is that most studies of MPs rely on resolved stars, posing a major challenge to the investigation of the MP phenomenon in distant galaxies. Here we search for integrated colors of old GCs that are sensitive to the MP phenomenon. To do this, we exploit integrated magnitudes of simulated GCs with MPs, and multiband Hubble Space Telescope photometry of 56 Galactic GCs, where MPs are widely studied, and characterized as part of the UV Legacy Survey of Galactic GCs. We find that both integrated CF275W,F336W,F438W and mF275W - mF814W colors strongly correlate with the iron abundance of the host GC. To second order, the pseudo two-color diagram built with these integrated colors is sensitive to the MP phenomenon. In particular, once the dependence on cluster metallicity is removed, the color residuals depend on the maximum internal helium variation within GCs and on the fraction of second-generation stars. This diagram, which we define here for Galactic GCs, has the potential to detect and characterize MPs from integrated photometry of old GCs, thus providing the possibility to extend their investigation outside the Local Group.

Keywords: Globular star clusters
The Impact of Shocks on the Vertical Structure of Eccentric Disks. Accretion disks whose matter follows eccentric orbits can arise in multiple astrophysical situations. Unlike circular orbit disks, the vertical gravity in eccentric disks varies around the orbit. In this paper, we investigate some of the dynamical effects of this varying gravity on the vertical structure using 1D hydrodynamics simulations of individual gas columns assumed to be mutually noninteracting. We find that time-dependent gravitational pumping generically creates shocks near pericenter; the energy dissipated in the shocks is taken from the orbital energy. Because the kinetic energy per unit mass in vertical motion near pericenter can be large compared to the net orbital energy, the shocked gas can be heated to nearly the virial temperature, and some of it becomes unbound. These shocks affect larger fractions of the disk mass for larger eccentricity and/or disk aspect ratio. If the orbit can be maintained despite orbital energy loss, diverse initial structures evolve in only a few orbits so that they follow a limit cycle characterized by a low-entropy midplane and a much higher entropy outer layer. In favorable cases (such as the tidal disruption of stars by supermassive black holes), these effects could be a potentially important energy dissipation and mass-loss mechanism.

Keywords: Accretion, Hydrodynamical simulations, Black hole physics, Gravitation
Formation and Characteristics of Filament Threads in Double-dipped Magnetic Flux Tubes. As one of the main formation mechanisms of solar filament formation, the chromospheric evaporation-coronal condensation model has been confirmed by numerical simulations to explain the formation of filament threads very well in flux tubes with single dips. However, coronal magnetic extrapolations indicated that some magnetic field lines might possess more than one dip. It is expected that the formation process would be significantly different in this case compared to a single-dipped magnetic flux tube. In this paper, based on the evaporation-condensation model, we study filament thread formation in double-dipped magnetic flux tubes by numerical simulations. We find that only with particular combinations of magnetic configuration and heating, e.g., concentrated localized heating and a long magnetic flux tube with deep dips, can two threads form and persist in a double-dipped magnetic flux tube. Comparing our parametric survey with observations, we conclude that such magnetically connected threads due to multiple dips are more likely to exist in quiescent filaments than in active-region filaments. Moreover, we find that these threads are usually shorter than independently trapped threads, which might be one of the reasons why quiescent filaments have short threads. These characteristics of magnetically connected threads could also explain barbs and vertical threads in quiescent filaments.

Keywords: Hydrodynamical simulations, Solar filaments, Solar corona
Quantifying Variability of Young Stellar Objects in the Mid-infrared Over 6 Years with the Near-Earth Object Wide-field Infrared Survey Explorer. Variability in young stellar objects (YSOs) can be caused by various time-dependent phenomena associated with star formation, including accretion rates, geometric changes in the circumstellar disks, stochastic hydromagnetic interactions between stellar surfaces and inner-disk edges, reconnections within the stellar magnetosphere, and hot/cold spots on stellar surfaces. We uncover and characterize ~1700 variables from a sample of ~5400 YSOs in nearby low-mass star-forming regions using mid-IR light curves obtained from the 6.5 yr Near-Earth Object Wide-field Infrared Survey Explorer All Sky Survey. The mid-IR variability traces a wide range of dynamical, physical, and geometrical phenomenon. We classify six types of YSO mid-IR variability based on their light curves: secular variability (linear, curved, and periodic) and stochastic variability (burst, drop, and irregular). YSOs in earlier evolutionary stages have higher fractions of variables and higher amplitudes for the variability, with the recurrence timescale of FUor-type outbursts (defined here as ΔW1 or ΔW2 &gt; 1 mag followed by inspection of candidates) of ~1000 yr in the early embedded protostellar phase. Known eruptive young stars and subluminous objects show fractions of variables similar to the fraction (~55%) found in typical protostars, suggesting that these two distinct types are not distinct in variability over the 6.5 yr timescale. Along with brightness variability, we also find a diverse range of secular color variations, which can be attributed to a competitive interplay between the variable accretion luminosity of the central source and the variable extinction by material associated with the accretion process.

Keywords: Young stellar objects
Turbulent Magnetic Dynamos with Halo Lags, Winds, and Jets. This paper presents scale-invariant/self-similar galactic magnetic dynamo models based on the classic equations and compares them qualitatively to recently observed magnetic fields in edge-on spiral galaxies. We classify the axially symmetric dynamo magnetic field by its separate sources, advected flux, and subscale turbulence. We ignore the diffusion term under plausible physical conditions. There is a time dependence determined by globally conserved quantities. We show that magnetic scale heights increase with radius and wind velocity. We suggest that active galactic nucleus (AGN) outflow is an important element of the large-scale galactic dynamo, based on the dynamo action of increasing subscale vorticity. This leads us to predict a correlation between the morphology of coherent galactic magnetic field (i.e., extended polarized flux) and the presence of an AGN.

Keywords: Cosmic magnetic fields theory, Disk galaxies, Extragalactic magnetic fields
The Active Fraction of Massive Black Holes in Dwarf Galaxies. The population of massive black holes (MBHs) in dwarf galaxies is elusive, but fundamentally important to understand the coevolution of black holes with their hosts and the formation of the first collapsed objects in the universe. While some progress was made in determining the X-ray detected fraction of MBHs in dwarfs, with typical values ranging from 0%-6%, their overall active fraction, ${ \mathcal A }$ , is still largely unconstrained. Here, we develop a theoretical model to predict the multiwavelength active fraction of MBHs in dwarf galaxies starting from first principles and based on the physical properties of the host, namely, its stellar mass and angular momentum content. We find multiwavelength active fractions for MBHs, accreting at typically low rates, ranging from 5%-22%, and increasing with the stellar mass of the host as ${ \mathcal A }$ $\sim \,{\left({\mathrm{log}}_{10}{M}_{\star }\right)}^{4.5}$ . If dwarfs are characterized by low-metallicity environments, the active fraction may reach ~30% for the most massive hosts. For galaxies with stellar mass in the range of 107 &lt; M⋆[ M⊙] &lt; 1010, our predictions are in agreement with occupation fractions derived from simulations and semi-analytical models. Additionally, we provide a fitting formula to predict the probability of finding an active MBH in a dwarf galaxy from observationally derived data. This model will be instrumental to guide future observational efforts to find MBHs in dwarfs. The James Webb Space Telescope, in particular, will play a crucial role in detecting MBHs in dwarfs, possibly uncovering active fractions ~3 times larger than current X-ray surveys.

Keywords: Intermediate-mass black holes, Supermassive black holes, Black holes, Dwarf galaxies, Low-luminosity active galactic nuclei, Active galactic nuclei, Galaxy evolution