Sazuna/UAT_keywords huggingface dataset:
Drifting Pulsation Structure at the Very Beginning of the 2017 September 10 Limb Flare. Drifting pulsation structures (DPSs) are important radio fine structures usually observed at the beginning of eruptive solar flares. It has been suggested that DPSs carry important information on the energy release processes in solar flares. We study DPS observed in an X8.2-class flare on 2017 September 10 in the context of spatial and spectral diagnostics provided by microwave, EUV, and X-ray observations. We describe DPS and its substructures that were observed for the first time. We use a new wavelet technique to reveal characteristic periods in DPS and their frequency bands. Comparing the periods of pulsations found in this DPS with those in previous DPSs, we found new very short periods in the 0.09-0.15 s range. We present Expanded Owens Valley Solar Array images and spectra of microwave sources observed during the DPS. This DPS at its very beginning has pulsations in two frequency bands (1000-1300 MHz and 1600-1800 MHz), which are interconnected by fast drifting bursts. We show that these double-band pulsations started just at the moment when the ejected filament splits apart in a tearing motion at the location where a signature of the flare current sheet later appeared. Using the standard flare model and previous observations of DPSs, we interpret these double-band pulsations as a radio signature of superthermal electrons trapped in the rising magnetic rope and flare arcade at the moment when the flare magnetic reconnection starts. The results are discussed in a scenario with the plasmoid in the rising magnetic rope.

Keywords: Solar radio emission, Solar flares
Black Hole Hyperaccretion in Collapsars. II. Gravitational Waves. As progenitors of gamma-ray bursts (GRBs), the core collapse of massive stars and the coalescence of compact object binaries are believed to be powerful sources of gravitational waves (GWs). In the collapsar scenario, a rotating stellar-mass black hole (BH) surrounded by a hyperaccretion disk might be active in the center of a massive collapsar, which is one of the plausible central engines of long GRBs. Such a BH hyperaccretion disk would be in a state of a neutrino-dominated accretion flow (NDAF) at the initial stage of the accretion process; meanwhile, the jets attempt to break out from the envelope and circumstellar medium to power GRBs. In addition to collapsars, BH hyperaccretion systems are important sources of neutrinos and GWs. In this paper, we investigate the GW emission generated by the anisotropic neutrino emission from NDAFs in collapsar scenarios. As the results indicate, the typical frequency of GWs is ∼1-100 Hz, and the masses and metallicities of the progenitor stars have slight effects on the GW strains. The GWs from NDAFs might be detected by operational or planned detectors at a distance of 10 kpc. Moreover, comparisons of the detectable GWs from collapsars, NDAFs, and GRB jets (internal shocks) are displayed. By combining the electromagnetic counterparts, neutrinos, and GWs, one may constrain the characteristics of collapsars and central BH accretion systems.

Keywords: Accretion, Gamma-ray bursts, Core-collapse supernovae, Neutrino astronomy, Relativistic jets, Stellar mass black holes, Gravitational waves
Expanding the Y Dwarf Census with Spitzer Follow-up of the Coldest CatWISE Solar Neighborhood Discoveries. We present Spitzer 3.6 and 4.5 μm follow-up of 170 candidate extremely cool brown dwarfs newly discovered via the combination of Wide-field Infrared Survey Explorer (WISE) and NEOWISE imaging at 3-5 μm. CatWISE, a joint analysis of archival WISE and NEOWISE data, has improved upon the motion measurements of AllWISE by leveraging a &gt;10× time baseline enhancement, from 0.5 yr (AllWISE) to 6.5 yr (CatWISE). As a result, CatWISE motion selection has yielded a large sample of previously unrecognized brown dwarf candidates, many of which have archival detections exclusively in the WISE 4.6 μm (W2) channel, suggesting that they could be both exceptionally cold and nearby. Where these objects go undetected in WISE W1 (3.4 μm), Spitzer can provide critically informative detections at 3.6 μm. Of our motion-confirmed discoveries, 17 have a best-fit Spitzer [3.6]-[4.5] color most consistent with spectral type Y. It is likely that CWISEP J144606.62-231717.8 (μ ≈ 1"3 yr-1) is the reddest, and therefore potentially coldest, member of our sample with a very uncertain [3.6]-[4.5] color of 3.71 ± 0.44 mag. We also highlight our highest proper-motion discovery, WISEA J153429.75-104303.3, with μ ≈ 2"7 yr-1. Given that the prior list of confirmed and presumed Y dwarfs consists of just 27 objects, the Spitzer follow-up presented in this work has substantially expanded the sample of identified Y dwarfs. Our new discoveries thus represent significant progress toward understanding the bottom of the substellar mass function, investigating the diversity of the Y dwarf population, and selecting optimal brown dwarf targets for James Webb Space Telescope spectroscopy.

Keywords: Brown dwarfs, Y dwarfs, Solar neighborhood, Proper motions, T dwarfs
Pulsational Pair-instability Supernovae. II. Neutrino Signals from Pulsations and Their Detection by Terrestrial Neutrino Detectors. A Pulsational Pair-instability supernova (PPISN) evolves from a massive star with a mass ∼80-140 M⊙ that develops electron-positron pair-instability after hydrostatic He-burning in the core has finished. In Leung et al. (Paper I), we examined the evolutionary tracks and the pulsational mass-loss history of this class of stars. In this paper, we analyze the thermodynamical history to explore the neutrino observables of PPISNe. We compute the neutrino light curves and spectra during pulsation. We then study the detailed neutrino emission profiles of these stars and estimate the expected neutrino detection count for different terrestrial neutrino detectors, including, e.g., KamLAND and Super-Kamiokande. Finally, we compare the neutrino pattern of PPISN with other types of supernovae based on a canonical 10 kt detector. The predicted neutrino signals can provide an early warning for telescopes to trace for the early time optical signals. The implications of neutrino physics on the expected detection are also discussed.

Keywords: Supernova neutrinos, Supernovae, Stellar pulsations
SOFIA/HAWC+ View of an Extremely Luminous Infrared Galaxy: WISE 1013+6112. We present far-infrared (FIR) properties of an extremely luminous infrared galaxy (ELIRG) at zspec = 3.703, WISE J101326.25+611220.1 (WISE 1013+6112). This ELIRG is selected as an IR-bright dust-obscured galaxy based on the photometry from the Sloan Digital Sky Survey and the Wide-field Infrared Survey Explorer (WISE). In order to derive its accurate IR luminosity, we perform follow-up observations at 89 and 154 μm using the High-resolution Airborne Wideband Camera-plus (HAWC+) on board the 2.7 m Stratospheric Observatory For Infrared Astronomy (SOFIA) telescope. We conduct spectral energy distribution (SED) fitting with CIGALE using 15 photometric data (0.4-1300 μm). We successfully pin down FIR SED of WISE 1013+6112 and its IR luminosity is estimated to be LIR = (1.62 ± 0.08) × 1014L⊙, making it one of the most luminous IR galaxies in the universe. We determine the dust temperature of WISE 1013+6112 is Tdust = 89 ± 3 K, which is significantly higher than that of other populations such as submillimeter galaxies and FIR-selected galaxies at similar IR luminosities. The resultant dust mass is Mdust = (2.2 ± 0.1) × 108 M⊙. This indicates that WISE 1013+6112 has a significant active galactic nucleus and star-forming activity behind a large amount of dust.

Keywords: Supermassive black holes, Active galaxies, Infrared galaxies, Quasars
Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?. Recently, transmission spectroscopy in the atmospheres of the TRAPPIST-1 planets revealed flat and featureless absorption spectra, which rule out cloud-free, hydrogen-dominated atmospheres. Earth-sized planets orbiting TRAPPIST-1 likely have either a clear or a cloudy/hazy, hydrogen-poor atmosphere. In this paper, we investigate whether a proposed formation scenario is consistent with expected atmospheric compositions of the TRAPPIST-1 planets. We examine the amount of hydrogen-rich gas that TRAPPIST-1-like planets accreted from the ambient disk until disk dispersal. Since TRAPPIST-1 planets are trapped into a resonant chain, we simulate disk gas accretion onto a migrating TRAPPIST-1-like planet. We find that the amount of accreted hydrogen-rich gas is as small as 10-2 wt% and 0.1 wt% for TRAPPIST-1 b and 1 c, 10-2 wt% for 1 d, 1 wt% for 1 e, a few wt% for 1 f and 1 g and 1 wt% for 1 h, respectively. We also calculate the long-term thermal evolution of TRAPPIST-1-like planets after disk dissipation and estimate the mass loss of their hydrogen-rich atmospheres driven by stellar X-ray and UV irradiation. We find that all the accreted hydrogen-rich atmospheres can be lost via hydrodynamic escape. Therefore, we conclude that TRAPPIST-1 planets should have no primordial hydrogen-rich gases but secondary atmospheres such as a Venus-like one and water vapor, if they currently retain atmospheres.

Keywords: Exoplanets, Exoplanet formation, Planet formation, Exoplanet atmospheres
The Influence of Stellar Contamination on the Interpretation of Near-infrared Transmission Spectra of Sub-Neptune Worlds around M-dwarfs. The impact of unocculted stellar surface heterogeneities in the form of cool spots and hot faculae on the spectrum of a transiting planet has been a daunting problem for the characterization of exoplanet atmospheres. The wavelength-dependent nature of stellar surface heterogeneities imprinting their signatures on planetary transmission spectra are of concern particularly for systems of sub-Neptunes orbiting M-dwarfs. Here we present a systematic exploration of the impact of this spot-contamination on simulated near-infrared transmission spectra of sub-Neptune planets. From our analysis, we find that improper correction for stellar surface heterogeneities on transmission spectra can lead to significant bias when inferring planetary atmospheric properties. However, this bias is negligible for lower fractions of heterogeneities (&lt;1%). Additionally, we find that acquiring a priori knowledge of stellar heterogeneities does not improve precision in constraining planetary parameters if the heterogeneities are appropriately marginalized within a retrieval; however, these are conditional on our confidence of stellar atmospheric models being accurate representations of the true photosphere. In sum, to acquire unbiased constraints when characterizing planetary atmospheres with the James Webb Space Telescope, we recommend performing joint retrievals of both the disk-integrated spectrum of the star and the stellar-contamination-corrected transmission spectrum.

Keywords: M dwarf stars, Exoplanet atmospheric composition , Starspots, Bayesian statistics, Hot Neptunes, Stellar activity, Radiative transfer, Spectroscopy, Exoplanet atmospheres
On Using Inspiraling Supermassive Binary Black Holes in the PTA Frequency Band as Standard Sirens to Constrain Dark Energy. Supermassive binary black holes (SMBBHs) in galactic centers may radiate gravitational waves (GW) in the nano-Hertz frequency band, which are expected to be detected by pulsar timing arrays (PTAs) in the near future. GW signals from individual SMBBHs at cosmic distances, if detected by PTAs, are potentially powerful standard sirens that can be used to independently measure distances and thus put constraints on cosmological parameters. In this paper, we investigate the constraint that may be obtained on the equation of state (w) of dark energy by using those SMBBHs, expected to be detected by the PTAs in the Square Kilometre Array (SKA) era. By considering both the currently available SMBBH candidates and mock SMBBHs in the universe resulting from a simple galaxy major merger model, we find that ∼200-3000 SMBBHs with chirp mass &gt;109 M⊙ are expected to be detected with a signal-to-noise ratio &gt;10 by SKA-PTA with conservative and optimistic settings and they can be used to put a constraint on w to an uncertainty of Δw ∼ 0.02-0.1. If further information on the mass and mass ratio of those SMBBHs can be provided by electromagnetic observations (e.g., chirp mass uncertainty ≲50%), the constraint may be further improved to a ≲0.01 level, as many more SMBBHs will be detected by SKA-PTA with relatively better distance measurements and can be used as the standard sirens.

Keywords: Supermassive black holes, Black hole physics, Pulsar timing method, Cosmological parameters, Fisher's Information, Gravitational wave astronomy, Active galactic nuclei, Gravitational waves, Dark energy
SCUBA-2 Ultra Deep Imaging EAO Survey (Studies). III. Multiwavelength Properties, Luminosity Functions, and Preliminary Source Catalog of 450 μm Selected Galaxies. We construct a SCUBA-2 450 μm map in the COSMOS field that covers an area of 300 arcmin2 and reaches a 1σ noise level of 0.65 mJy in the deepest region. We extract 256 sources detected at 450 μm with signal-to-noise ratios &gt;4.0 and analyze the physical properties of their multiwavelength counterparts. We find that most of the sources are at z ≲ 3, with a median of $z={1.79}_{-0.15}^{+0.03} \% $ . About ${35}_{-25}^{+32} \% $ of our sources are classified as starburst galaxies based on their total star formation rates (SFRs) and stellar masses (M*). By fitting the far-infrared spectral energy distributions, we find that our 450 μm selected sample has a wide range of dust temperatures (20 K ≲ Td ≲ 60 K), with a median of ${T}_{{\rm{d}}}={38.3}_{-0.9}^{+0.4}$ K. We do not find a redshift evolution in dust temperature for sources with ${L}_{\mathrm{IR}}\gt {10}^{12}\,{L}_{\odot }$ at z &lt; 3. However, we find a moderate correlation where the dust temperature increases with the deviation from the SFR-M* relation. The increase in dust temperature also correlates with optical morphology, which is consistent with merger-triggered starbursts in submillimeter galaxies. Our galaxies do not show the tight IRX-βUV correlation that has been observed in the local universe. We construct the infrared luminosity functions of our 450 μm sources and measure their comoving SFR densities (SFRDs). The contribution of the ${L}_{\mathrm{IR}}\gt {10}^{12}\,{L}_{\odot }$ population to the SFRD rises dramatically from z = 0 to 2 (∝(1 + z)3.9±1.1) and dominates the total SFRD at z ≳ 2.

Keywords: Luminosity function, Submillimeter astronomy, High-redshift galaxies, Galaxy evolution
Stellar Migration in Galaxy Disks Using the Chirikov Diffusion Rate. We are reexamining the problem of stellar migration in disk galaxies from a diffusion perspective. We use for the first time the formulation of the diffusion rates introduced by Chirikov, applied to both energy, E, and angular momentum, Lz, in self-consistent N-body experiments. We limit our study to the evolution of stellar disks well after the formation of the bar, in a regime of adiabatic evolution. We show that distribution functions of Chirikov diffusion rates have similar shapes, regardless of the simulations, but different slopes for energy and angular momentum. Distribution functions of derived diffusion timescales, TD, also have the same form for all simulations, but are different for TD(E) and TD(Lz). Diffusion timescales are strongly dependent on Lz. ${T}_{D}(E)\lesssim 1\,\mathrm{Gyr}$ in a Lz range roughly delimited by the set of stellar bar resonances (between the ultraharmonic resonance and the outer Lindblad resonance). Only particles with low Lz have ${T}_{D}({L}_{z})\lesssim 10\,\mathrm{Gyr}$ , I.e., the simulation length. In terms of mass fraction, 35%-42% turn out to diffuse energy in a characteristic timescale shorter than 10 Gyr, I.e., simulations length, while 60%-64% undergo the diffusion of the angular momentum on the same timescale. Both the diffusion of Lz and E are important to grasp the full characterization of the radial migration process, and we show that depending on the spatial region considered, one or the other diffusion dominates.

Keywords: Galaxy stellar disks, Galaxy dynamics, Galactic and extragalactic astronomy, Galaxy evolution, Barred spiral galaxies, N-body simulations, Dynamical evolution
Flame Acceleration in SN Ia Induced by the Burning of Local Unreacted Islands. The mechanism of type Ia supernova explosions is still unsolved due to the uncertainties in the processes of flame acceleration and the associated deflagration to detonation transition. In carbon-oxygen (C-O) white dwarfs, due to the well known Rayleigh-Taylor (R-T) instability and turbulent vortices in the R-T fingers, there exist unburned islands embedded in the downstream of the main flame front. The burning of such islands can be modeled by the spherical inward-propagating two-step C-O flame, which will accelerate while propagating inward due to the stretch effect and the Zel'Dovich mechanism. In turbulent flows under proper conditions, such acceleration can be further strengthened by turbulent mixing, possibly making the burning of these islands speed up to be supersonic. The supersonic burning of the embedded islands is then a source of heating that speeds up the main flame. Here we derive the relationship between the flame's spontaneous inward-propagating speed and the flame radius in consuming the unburned islands based on the Zel'Dovich mechanism in both laminar and turbulent flows. The calculation results show that, in suitable turbulent situation, I.e., for a C-O white dwarf with density 3.5 × 107 g cm-3, Reynolds number 1.0 × 1013, and integral scale 110 km, the island flame speed reaches the sound speed when the flame radius is 1.5 times the flame thickness, and then remains supersonic. Such supersonic combustion generates shock waves, which heat and speed up the main flame, and possibly lead to the initiation of global detonation.

Keywords: Shocks, Type Ia supernovae, Hydrodynamics, Astrophysical explosive burning
Investigation of Surface Effects of Simple Flux Tubes Using Numerical Simulations. We use the SPARC code for MHD simulations with monolithic flux tubes of varying subsurface topology. Our studies involve the interactions of waves caused by a single source with subsurface magnetic fields. Mode conversion causing acoustic power to trickle downwards along the flux tube has been described before and can be visualized in our simulations. We show that this downward propagation causes the flux tube to act as an isolated source, creating a characteristic surface wave field. Measuring this wave field at the surface reveals subsurface properties of the magnetic field topology. Using time-distance helioseismology, we demonstrate how to detect such a flux tube signal based on a group travel time delay of Δt = 282.6 s due to the wave packet spending time subsurface as a slow mode wave. Although the amplitude is small and generally superimposed by the full wave field, it can be detected if assumptions about Δt are made. We demonstrate this for a simulation with solar-like sources. This kind of study has the potential to reveal subsurface information of sunspots based on the analysis of a surface signal.

Keywords: Magnetohydrodynamics, Helioseismology, Sunspots, Solar physics, Solar magnetic fields, Magnetohydrodynamical simulations
Obscuring Fraction of Active Galactic Nuclei Implied by Supernova and Radiative Feedbacks. We study the obscuring structure of circumnuclear disks (CNDs) by considering supernova (SN) feedbacks from nuclear starburst and the effect of anisotropic radiative pressure from active galactic nuclei (AGNs). We suppose that the mass accretion onto a central supermassive black hole (SMBH) is triggered by SN-driven turbulence within CNDs, and we explore how the structures of CNDs depend on the BH mass (MBH) and AGN luminosity (LAGN). We find that the obscuring fraction (fobs) peaks at ∼10% of the Eddington luminosity (LEdd), and its maximal value is fobs ∼ 0.6 for less massive SMBHs (e.g., MBH &lt; 108 M⊙). This is because the scale height of CNDs is determined by the SN-driven accretion for a smaller LAGN, while the dusty molecular gas in CNDs is blown away by the radiation pressure from AGNs beyond the critical luminosity. On the other hand, for massive SMBHs (e.g., MBH &gt; 108 M⊙), fobs is always smaller than 0.2, and it is almost independent of LAGN because the scale height of CNDs is mainly controlled by the maximal star formation efficiency ( ${C}_{* ,\max }$ ) in CNDs. In comparison with the obscuring fractions suggested from the mid-infrared observations of nearby AGNs, the SN plus radiative feedback model with ${C}_{* ,\max }={10}^{-7}\,{\mathrm{yr}}^{-1}$ reproduces the observations for MBH = 108 M⊙ well. We also find that the intense starburst or the existence of dust-free absorbers inside CNDs are necessary for explaining X-ray observations.

Keywords: Active galaxies, Active galactic nuclei, Galaxy nuclei
Evolution from Spherical AGB Wind to Multipolar Outflow in Pre-planetary Nebula IRAS 17150-3224. We have mapped the pre-planetary nebula IRAS 17150-3224 in the 350 GHz continuum and CO J = 3-2 line at an angular resolution of ∼0"09 using the Atacama Large Millimeter/submillimeter Array. A continuum source is detected at the center of the nebula, elongated along the equatorial plane, likely tracing a dusty torus around the central source. Continuum emission is also detected on both sides of the central continuum source in the equatorial plane, probably resulting from interactions of collimated fast winds (CFWs) with envelope material in the equator. CO emission is detected along the optical lobe. Although the optical lobe appears as bipolar, the CO map shows that it is actually a quadrupolar outflow consisting of two overlapping bipolar outflows. Two additional younger bipolar outflows are also detected in CO, one at the lower latitude and the other along the equatorial plane. In the CO position-velocity maps, blueshifted absorption stripes are detected in the outflow emissions, due to absorption by a series of shells produced by a series of asymptotic giant branch (AGB) wind ejections. By modeling the morphology and kinematics of the AGB wind and outflows, we find that the AGB wind could have ended ∼1300 yr ago, the quadrupolar outflow was ejected ∼350 yr ago, and the two additional bipolar outflows were ejected ∼280 and 200 yr ago, respectively. The outflows could be produced either by bullets coming from an explosion, or by a precessing CFW with a time-dependent ejection velocity.

Keywords: Protoplanetary nebulae, Stellar jets, Post-asymptotic giant branch, Stellar mass loss, Asymptotic giant branch stars, Stellar winds