Sazuna/UAT_keywords huggingface dataset:
Effects of Vertical Advection on Multimessenger Signatures of Black Hole Neutrino-dominated Accretion Flows in Compact Binary Coalescences. In the coalescence events of binary neutron star (NS) or a black hole (BH) and an NS, a BH hyperaccretion disk might be eventually formed. At very high mass accretion rates, MeV neutrinos will be emitted from this disk, which is called a neutrino-dominated accretion flow (NDAF). Neutrino annihilation in the space out of the disk is energetic enough to launch ultrarelativistic jets to power gamma-ray bursts. Moreover, vertical advection might exist in NDAFs, which can generate the magnetic buoyancy bubbles to release gamma-ray photons. In this paper, we visit the effects of the vertical advection in NDAFs on the disk structure and gamma-ray and neutrino luminosities for different accretion rates. Then we study the anisotropic emission of kilonovae and the following gravitational waves (GWs) driven by the gamma-ray photons and neutrinos from NDAFs. Comparing NDAFs without vertical advection, the neutrino luminosity and GW strains slightly decrease for the case with vertical advection, and the kilonovae will be brightened by the injected gamma-ray photons. The future joint multimessenger observations might distinguish whether the vertical advection exists in NDAFs or not after compact binary coalescences.

Keywords: Accretion, Gamma-ray bursts, Black holes, Neutrino astronomy, Transient sources, Gravitational waves
Hubble Space Telescope Observations of Tadpole Galaxies Kiso3867, SBS0, SBS1, and UM461. Tadpole galaxies are metal-poor dwarfs with typically one dominant star-forming region, giving them a head-tail structure when inclined. A metallicity drop in the head suggests that gas accretion with even lower metallicity stimulated the star formation. Here we present multiband Hubble Space Telescope WFC3 and Advanced Camera for Surveys images of four nearby (&lt;25 Mpc) tadpoles, SBS0, SBS1, Kiso3867, and UM461, selected for their clear metallicity drops shown in previous spectroscopic studies. The properties of the star complexes and compact clusters are measured. Each galaxy contains from three to 10 young stellar complexes with 103-105 M ⊙ of stars ~3-10 Myr old. Between the complexes, the disk has a typical age of ~3 Gyr. Numerous star clusters cover the galaxies, both inside and outside the complexes. The combined cluster mass function, made by normalizing the masses and counts before stacking, is a power law with a slope of -1.12 ± 0.14 on a log-log plot and the combined distribution function of cluster lifetime decays with age as t -0.65±0.24. A comparison between the summed theoretical Lyman continuum (LyC) emission from all the clusters, given their masses and ages, is comparable to or exceeds the LyC needed to excite the observed Hα in some galaxies, suggesting LyC absorption by dust or undetected gas in the halo, or perhaps galaxy escape.

Keywords: Blue compact dwarf galaxies, Young star clusters, Star forming regions
Effects of Supra-arcade Downflows Interacting with the Postflare Arcade. Supra-arcade downflows (SADs) are dark voids descending through plasma above the postflare arcade. Although they are generally viewed as byproducts of flare reconnections in the corona, the nature of SADs is under debate. Here we investigated six distinct episodes of SADs observed in the post-maximum phase of an M-class flare of 2013 April 11. Differential emission measure analysis revealed that SAD cases occurring close to the flare maximum contain an enhanced hot plasma component at 5-7 MK whereas those occurring later exhibit a depression in hot plasma at 7-12 MK compared to the ambient supra-arcade plasma. On-disk location of the flare enabled us to examine in detail the interaction of SADs with the postflare arcade, whose effects include (1) transverse oscillations of period ~160 s in the supra-arcade rays in the wake of voids, (2) footpoint brightening in 1700 Å whose peak is delayed by 22-46 s with respect to the SAD's arrival at the top of the arcade, and (3) EUV intensity perturbations expanding and propagating with a speed of ~400 km s-1. On the other hand, due to line-of-sight confusion in the optically thin corona, the ribbon enhancement following the interaction produces an illusion of plasma rebound at the top of the arcade, where the interaction fails to yield significant plasma heating. These effects indicate that the interaction mainly generates MHD waves propagating toward the surface, which may further produce quasi-periodic brightening at flare ribbons, therefore contributing to gradual phase emission from quasi-periodic EUV emission observed during the gradual phase of flares.

Keywords: Solar atmosphere, Solar flares, Solar magnetic reconnection, Solar coronal loops, The Sun
Optimal Spectral Lines for Measuring Chromospheric Magnetic Fields. This paper identifies spectral lines from X-ray to IR wavelengths which are optimally suited to measuring vector magnetic fields as high as possible in the solar atmosphere. Instrumental and Earth's atmospheric properties, as well as solar abundances, atmospheric properties, and elementary atomic physics are considered without bias toward particular wavelengths or diagnostic techniques. While narrowly focused investigations of individual lines have been reported in detail, no assessment of the comparative merits of all lines has ever been published. Although in the UV, on balance the Mg+ h and k lines near 2800 Å are optimally suited to polarimetry of plasma near the base of the solar corona. This result was unanticipated, given that longer-wavelength lines offer greater sensitivity to the Zeeman effect. While these lines sample optical depths photosphere to the coronal base, we argue that cores of multiple spectral lines provide a far more discriminating probe of magnetic structure as a function of optical depth than the core and inner wings of a strong line. Thus, together with many chromospheric lines of Fe+ between 2585 Å and the h line at 2803 Å, this UV region promises new discoveries concerning how the magnetic fields emerge, heat, and accelerate plasma as they battle to dominate the force and energy balance within the poorly understood chromosphere.

Keywords: Solar-terrestrial interactions, Quiet sun, Spectropolarimetry, Active sun
Implications of High-density, High-temperature Ridges Observed in Some Two-ribbon Flares. Several two-ribbon solar flares observed on the disk, notably including the Bastille flare of 2000 July 14, show an extended ridge of plasma running along the loop tops of the post-reconnection arcade. In that and two more recent examples, the ridge is visible in emission by Fe XXIV at roughly 17 MK, with a high, steadily increasing emission measure suggesting an expanding column of very dense plasma. We find that ridges are consistent with overhead views of long, vertical plasma sheets, such as seen above certain limb flares. Those vertical features show enhanced temperature and density over their entire lengths, making explanations in terms of termination shocks and evaporation collision seem less plausible. We use observations of several ridge events to argue in favor of compression and heating by slow magnetosonic shocks in the reconnection outflow. In this scenario, the ridge is built up as retracting flux piles hot, compressed plasma atop the post-flare arcade. Thanks to the overhead perspective offered by the ridge observations, we are able to measure the reconnection rate and show it to be consistent with the rate of increase in column emission measure across the ridge. This consistency supports the hypothesis that slow shocks and retraction compress the plasma seen in ridges, vertical plasma sheets, and possibly the high-temperature fans through which post-reconnection downflows are observed. Such a unified picture of these diverse features enhances our understanding of the role played by magnetic reconnection in solar flares.

Keywords: Solar flares
Demographics of the M-star Multiple Population in the Orion Nebula Cluster. We present updated results constraining multiplicity demographics for the stellar population of the Orion Nebula Cluster (ONC, a high-mass, high-density star-forming region), across primary masses 0.08-0.7 M ⊙. Our study utilizes archival Hubble Space Telescope data obtained with the Advanced Camera for Surveys using multiple filters (GO-10246). Previous multiplicity surveys in low-mass, low-density associations like Taurus identify an excess of companions to low-mass stars roughly twice that of the Galactic field and find the mass ratio distribution consistent with the field. Previously, we found the companion frequency to low-mass stars in the ONC is consistent with the Galactic field over mass ratios = 0.6-1.0 and projected separations = 30-160 au, without placing constraints on the mass ratio distribution. In this study, we investigate the companion population of the ONC with a double point-spread function (PSF) fitting algorithm sensitive to separations larger than 10 au (0.″025) using empirical PSF models. We identified 44 companions (14 new), and with a Bayesian analysis we estimate the companion frequency to low-mass stars in the ONC = 0.13 ${}_{-0.03}^{+0.05}$ and the index of the power-law fit to the mass ratio distribution = 2.08 ${}_{-0.85}^{+1.03}$ over all mass ratios and projected separations of 10-200 au. We find the companion frequency in the ONC is consistent with the Galactic field population, likely from states of high transient stellar density, and a probability of 0.002 that it is consistent with that of Taurus. We also find the ONC mass ratio distribution is consistent with the field and Taurus, potentially indicative of its primordial nature, a direct outcome of the star formation process.

Keywords: Binary stars, Hubble Space Telescope, Star forming regions, Star formation, Low mass stars, Visual binary stars
The Star Formation Rate of the Milky Way as Seen by Herschel. We present a new derivation of the Milky Way's current star formation rate (SFR) based on the data of the Herschel InfraRed Galactic Plane Survey (Hi-GAL). We estimate the distribution of the SFR across the Galactic plane from the star-forming clumps identified in the Hi-GAL survey and calculate the total SFR from the sum of their contributions. The estimate of the global SFR amounts to 2.0 ± 0.7 M ⊙ yr-1, of which 1.7 ± 0.6 M ⊙ yr-1 coming from clumps with reliable heliocentric distance assignment. This value is in general agreement with estimates found in the literature of last decades. The profile of SFR density averaged in Galactocentric rings is found to be qualitatively similar to others previously computed, with a peak corresponding to the Central Molecular Zone and another one around Galactocentric radius R gal ~ 5 kpc, followed by an exponential decrease as $\mathrm{log}({{\rm{\Sigma }}}_{\mathrm{SFR}}/[{M}_{\odot }\,{\mathrm{yr}}^{-1}\,{\mathrm{kpc}}^{-2}])=a\,{R}_{\mathrm{gal}}/[\mathrm{kpc}]+b$ , with a = -0.28 ± 0.01. In this regard, the fraction of SFR produced within and outside the solar circle is 84% and 16%, respectively; the fraction corresponding to the far outer Galaxy (R gal &gt; 13.5 kpc) is only 1%. We also find that, for R gal &gt; 3 kpc, our data follow a power law as a function of density, similarly to the Kennicutt-Schmidt relation. Finally, we compare the distribution of the SFR density across the face-on Galactic plane and those of median parameters, such as temperature, luminosity/mass ratio, and bolometric temperature, describing the evolutionary stage of Hi-GAL clumps. We found no clear correlation between the SFR and the clump evolutionary stage.

Keywords: Galaxy structure, Star formation, Milky Way Galaxy, Far infrared astronomy
DUVET: Spatially Resolved Observations of Star Formation Regulation via Galactic Outflows in a Starbursting Disk Galaxy. We compare 500 pc scale, resolved observations of ionized and molecular gas for the z ~ 0.02 starbursting disk galaxy IRAS08339+6517, using measurements from KCWI and NOEMA. We explore the relationship of the star-formation-driven ionized gas outflows with colocated galaxy properties. We find a roughly linear relationship between the outflow mass flux ( ${\dot{{\rm{\Sigma }}}}_{\mathrm{out}}$ ) and star formation rate surface density (ΣSFR), ${\dot{{\rm{\Sigma }}}}_{\mathrm{out}}\propto {{\rm{\Sigma }}}_{\mathrm{SFR}}^{1.06\pm 0.10}$ , and a strong correlation between ${\dot{{\rm{\Sigma }}}}_{\mathrm{out}}$ and the gas depletion time, such that ${\dot{{\rm{\Sigma }}}}_{\mathrm{out}}\propto {t}_{\mathrm{dep}}^{-1.1\pm 0.06}$ . Moreover, we find these outflows are so-called breakout outflows, according to the relationship between the gas fraction and disk kinematics. Assuming that ionized outflow mass scales with total outflow mass, our observations suggest that the regions of highest ΣSFR in IRAS08 are removing more gas via the outflow than through the conversion of gas into stars. Our results are consistent with a picture in which the outflow limits the ability of a region of a disk to maintain short depletion times. Our results underline the need for resolved observations of outflows in more galaxies.

Keywords: Starburst galaxies, Galaxy winds, Galaxy evolution, Galaxies
Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models. Observations show an almost ubiquitous presence of extra mixing in low-mass upper giant branch stars. The most commonly invoked explanation for this is thermohaline mixing. One-dimensional stellar evolution models include various prescriptions for thermohaline mixing, but the use of observational data directly to discriminate between thermohaline prescriptions has thus far been limited. Here, we propose a new framework to facilitate direct comparison: using carbon-to-nitrogen measurements from the Sloan Digital Sky Survey-IV APOGEE survey as a probe of mixing and a fluid parameter known as the reduced density ratio from one-dimensional stellar evolution programs, we compare the observed amount of extra mixing on the upper giant branch to predicted trends from three-dimensional fluid dynamics simulations. Using this method, we are able to empirically constrain how mixing efficiency should vary with the reduced density ratio. We find the observed amount of extra mixing is strongly correlated with the reduced density ratio and that trends between reduced density ratio and fundamental stellar parameters are robust across choices for modeling prescription. We show that stars with available mixing data tend to have relatively low density ratios, which should inform the regimes selected for future simulation efforts. Finally, we show that there is increased mixing at low reduced density ratios, which is consistent with current hydrodynamical models of thermohaline mixing. The introduction of this framework sets a new standard for theoretical modeling efforts, as validation for not only the amount of extra mixing, but trends between the degree of extra mixing and fundamental stellar parameters is now possible.

Keywords: Stellar interiors, Red giant branch, Abundance ratios, Dredge-up, Hydrodynamics, Stellar abundances, Red giant bump, Astrophysical fluid dynamics, Stellar evolution
Photometric and Spectroscopic Study of the EXor-like Eruptive Young Star Gaia19fct. Gaia19fct is one of the Gaia-alerted eruptive young stars that has undergone several brightening events. We conducted monitoring observations using multifilter optical and near-infrared photometry, as well as near-infrared spectroscopy, to understand the physical properties of Gaia19fct and investigate whether it fits into the historically defined two classes. We present the analyses of light curves, color variations, spectral lines, and CO modeling. The light curves show at least five brightening events since 2015, and the multifilter color evolutions are mostly gray. The gray evolution indicates that bursts are triggered by mechanisms other than extinction. Our near-infrared spectra exhibit both absorption and emission lines and show time variability throughout our observations. We found lower rotational velocity and lower temperature from the near-infrared atomic absorption lines than from the optical lines, suggesting that Gaia19fct has a Keplerian rotating disk. The CO overtone features show a superposition of absorption and emission components, which is unlike other young stellar objects. We modeled the CO lines, and the result suggests that the emission and absorption components are formed in different regions. We found that although Gaia19fct exhibits characteristics of both types of eruptive young stars, FU Orionis-type objects and EX Lupi-type objects, it shows more similarity with EXors in general.

Keywords: High resolution spectroscopy, Multi-color photometry, FU Orionis stars, Light curves, Young stellar objects, Circumstellar disks
Search for Quasiperiodic Oscillations in Precursors of Short and Long Gamma-Ray Bursts. The precursors of short and long gamma-ray bursts (SGRBs and LGRBs) can serve as probes of their progenitors, as well as shedding light on the physical processes of mergers or core-collapse supernovae. Some models predict the possible existence of quasiperiodic oscillations (QPOs) in the precursors of SGRBs. Although many previous studies have performed QPO searches in the main emission of SGRBs and LGRBs, so far there were no systematic QPO searches in their precursors. In this work, we perform a detailed QPO search in the precursors of SGRBs and LGRBs detected by Fermi/Gamma-ray Burst Monitor (GBM) from 2008 to 2019 using the power density spectrum (PDS) in the frequency domain and Gaussian processes in the time domain. We do not find any convinced QPO signal with significance above 3σ, possibly due to the low fluxes of precursors. Finally, the PDS continuum properties of both the precursors and main emissions are also studied for the first time, and no significant difference is found in the distributions of the PDS slope for precursors and main emissions in both SGRBs and LGRBs.

Keywords: Gamma-ray bursts
EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension. The primordial He abundance Y P is a powerful probe of cosmology. Currently, Y P is best determined by observations of metal-poor galaxies, while there are only a few known local extremely metal-poor (&lt;0.1Z ⊙) galaxies (EMPGs) having reliable He/H measurements with He I λ10830 near-infrared (NIR) emission. Here we present deep Subaru NIR spectroscopy for 10 EMPGs. Combining the existing optical data, He/H values of 5 out of the 10 EMPGs are reliably derived by the Markov chain Monte Carlo algorithm. Adding the existing 3 EMPGs and 51 moderately metal-poor (0.1-0.4Z ⊙) galaxies with reliable He/H estimates, we obtain ${Y}_{{\rm{P}}}={0.2370}_{-0.0034}^{+0.0033}$ by linear regression in the (He/H) - (O/H) plane, where we increase the number of EMPGs from three to eight anchoring He/H of the most metal-poor gas in galaxies. Although our Y P measurement and previous measurements are consistent, our result is slightly (~1σ) smaller due to our EMPGs. Including the existing primordial deuterium D P measurement, we constrain the effective number of neutrino species N eff and the baryon-to-photon ratio η showing ≳1-2σ tensions with the Standard Model and Planck Collaboration et al. (2020). Motivated by the tensions, we allow the degeneracy parameter of the electron neutrino ξ  e , as well as N eff and η, to vary. We obtain ${\xi }_{e}={0.05}_{-0.02}^{+0.03}$ , ${N}_{\mathrm{eff}}={3.11}_{-0.31}^{+0.34}$ , and $\eta \times {10}^{10}={6.08}_{-0.06}^{+0.06}$ from the Y P and D P measurements with a prior of η taken from Planck Collaboration et al. Our constraints suggest a lepton asymmetry and allow for a high value of N eff within the 1σ level, which could mitigate the Hubble tension.

Keywords: Galaxy abundances, Big Bang nucleosynthesis, Galaxy chemical evolution, Cosmological parameters
A Large (≈ 1 pc) Contracting Envelope Around the Prestellar Core L1544. Prestellar cores, the birthplace of Sun-like stars, form from the fragmentation of the filamentary structure that composes molecular clouds, from which they must inherit at least partially the kinematics. Furthermore, when they are on the verge of gravitational collapse, they show signs of subsonic infall motions. How extended these motions are, which depends on how the collapse occurs, remains largely unknown. We want to investigate the kinematics of the envelope that surrounds the prototypical prestellar core L1544, studying the cloud-core connection. To our aims, we observed the HCO+ (1-0) transition in a large map. HCO+ is expected to be abundant in the envelope, making it an ideal probe of the large-scale kinematics in the source. We modeled the spectrum at the dust peak by means of a nonlocal thermodynamical equilibrium radiative transfer. In order to reproduce the spectrum at the dust peak, a large (~1 pc) envelope is needed, with low density (tens of cm-3 at most) and contraction motions, with an inward velocity of ≈ 0.05 km s-1. We fitted the data cube using the Hill5 model, which implements a simple model for the optical depth and excitation temperature profiles along the line of sight, in order to obtain a map of the infall velocity. This shows that the infall motions are extended, with typical values in the range 0.1-0.2 km s-1. Our results suggest that the contraction motions extend in the diffuse envelope surrounding the core, which is consistent with recent magnetic field measurements in the source, which showed that the envelope is magnetically supercritical. *This work is based on observations carried out with the IRAM 30m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Keywords: Astrochemistry, Star formation, Gravitational collapse, Low mass stars, Interstellar medium
Harvesting BAT-GUANO with NITRATES (Non-Imaging Transient Reconstruction and Temporal Search): Detecting and Localizing the Faintest Gamma-Ray Bursts with a Likelihood Framework. The detection of the gravitational wave (GW) counterpart GRB 170817A, underluminous compared to the cosmological gamma-ray burst (GRB) population by a factor of 10,000, motivates significant effort in detecting and localizing a dim, nearby, and slightly off-axis population of short GRBs. Swift's Burst Alert Telescope (BAT) is one of the most sensitive GRB detectors in operation, and the only one that regularly localizes GRBs to arcminute precision, critical to rapid follow-up studies. However, the utility of BAT in targeted subthreshold searches had been historically curtailed by the unavailability of the necessary raw data for analysis. The new availability of time-tagged event data from the GUANO system motivates a renewed focus on developing sensitive targeted search analysis techniques to maximally exploit these data. While computationally cheap, we show that the typical coded-mask deconvolution imaging is limited in its sensitivity due to several factors. We formalize a maximum likelihood framework for the analysis of BAT data wherein signals are forward modeled through the full instrument response, and-coupled with the development of new response models-demonstrate its superior sensitivity to typical imaging via archival comparisons, injection campaigns, and a large number of low-latency GRB discoveries and confirmed arcminute localizations to date. We also demonstrate independent localization of some out-of-field-of-view GRBs for the first time. NITRATES's increased sensitivity boosts the discovery rate of GRB 170817A-like events in BAT by a factor of at least 3-4×, along with enabling joint analyses and searches with other GRB, GW, neutrino, and FRB instruments. We provide public access to the response functions and search pipeline code.

Keywords: Space telescopes, Gamma-ray bursts, Gravitational wave sources