Sazuna/UAT_keywords huggingface dataset:
Solar Coronal Magnetic Field Extrapolation from Synchronic Data with AI-generated Farside. Solar magnetic fields play a key role in understanding the nature of the coronal phenomena. Global coronal magnetic fields are usually extrapolated from photospheric fields, for which farside data is taken when it was at the frontside, about two weeks earlier. For the first time we have constructed the extrapolations of global magnetic fields using frontside and artificial intelligence (AI)-generated farside magnetic fields at a near-real time basis. We generate the farside magnetograms from three channel farside observations of Solar Terrestrial Relations Observatory (STEREO) Ahead (A) and Behind (B) by our deep learning model trained with frontside Solar Dynamics Observatory extreme ultraviolet images and magnetograms. For frontside testing data sets, we demonstrate that the generated magnetic field distributions are consistent with the real ones; not only active regions (ARs), but also quiet regions of the Sun. We make global magnetic field synchronic maps in which conventional farside data are replaced by farside ones generated by our model. The synchronic maps show much better not only the appearance of ARs but also the disappearance of others on the solar surface than before. We use these synchronized magnetic data to extrapolate the global coronal fields using Potential Field Source Surface (PFSS) model. We show that our results are much more consistent with coronal observations than those of the conventional method in view of solar active regions and coronal holes. We present several positive prospects of our new methodology for the study of solar corona, heliosphere, and space weather.

Keywords: Astronomical models, The Sun, Convolutional neural networks, Space weather, Solar corona, Solar magnetic fields
Do Afterglow Synchrotron Radiations Follow the L<SUB>p,iso</SUB>-E<SUB>p,z</SUB>-Γ<SUB>0</SUB> Relation of Gamma-Ray Bursts? The Cases of GRBs 190114C, 130427A, and 180720B. Bimodal spectral energy distributions (SEDs) of gamma-ray burst (GRB) afterglow of GRBs 190114C, 130427A, and 180720B confirm that they are originated from the synchrotron emission (Syn) and synchrotron self-Compton scattering (SSC) process of electrons accelerated in the jets. The radiation mechanism and the physics of the observed spectrum-luminosity/energy relations of GRBs remain as open questions. By extracting the Syn component through fitting their early afterglow SEDs with the Syn+SSC model, we find that their luminosity (Lsyn), peak energy (Ep,syn,z), and the Lorentz factor of the afterglow fireball (Γt) follow the Lp,iso-Ep,z-Γ0 relation of prompt gamma rays, where Lp,iso is the isotropic luminosity, Ep,z is the peak energy of the $\nu {f}_{\nu }$ spectrum in the burst frame, and Γ0 is the initial Lorentz factor of the fireball. To examine whether late afterglows are consistent with this relation, we calculate the synchrotron component at late afterglows. It is found that they also follow the same Lp,iso-Ep,z-Γ0 relation, albeit they are not consistent with the Lp,iso-Ep,z relation. Our results may imply that the Lp,iso-Ep,z-Γ0 relation would be a universal feature of synchrotron radiations of electrons accelerated in GRB jets throughout the prompt and afterglow phases among GRBs. Its origin is not fully understood, and possible explanations are briefly discussed.

Keywords: Gamma-ray bursts, Non-thermal radiation sources
Orbital Foregrounds for Ultra-short Duration Transients. Reflections from objects in Earth orbit can produce subsecond, star-like optical flashes similar to astrophysical transients. Reflections have historically caused false alarms for transient surveys, but the population has not been systematically studied. We report event rates for these orbital flashes using the Evryscope Fast Transient Engine, a low-latency transient detection pipeline for the Evryscopes. We select single-epoch detections likely caused by Earth satellites and model the event rate as a function of both magnitude and sky position. We measure a rate of ${1800}_{-280}^{+600}$ sky-1 hr-1, peaking at mg = 13.0, for flashes morphologically degenerate with real astrophysical signals in surveys like the Evryscopes. Of these, ${340}_{-85}^{+150}$ sky-1 hr-1 are bright enough to be visible to the naked eye in typical suburban skies with a visual limiting magnitude of V ≈ 4. These measurements place the event rate of orbital flashes orders of magnitude higher than the combined rate of public alerts from all active all-sky fast-timescale transient searches, including neutrino, gravitational-wave, gamma-ray, and radio observatories. Short-timescale orbital flashes form a dominating foreground for untriggered searches for fast transients in low-resolution, wide-angle surveys. However, events like fast radio bursts with arcminute-scale localization have a low probability (∼10-5) of coincidence with an orbital flash, allowing optical surveys to place constraints on their potential optical counterparts in single images. Upcoming satellite internet constellations, like SpaceX Starlink, are unlikely to contribute significantly to the population of orbital flashes in normal operations.

Keywords: Sky surveys, Transient detection, Wide-field telescopes
Dependence of the IRX-β Dust Attenuation Relation on Metallicity and Environment. We use a sample of star-forming field and protocluster galaxies at z = 2.0-2.5 with Keck/MOSFIRE K-band spectra, a wealth of rest-frame ultraviolet (UV) photometry, and Spitzer/MIPS and Herschel/PACS observations, to dissect the relation between the ratio of infrared (IR) to UV luminosity (IRX) versus UV slope (β) as a function of gas-phase metallicity ( $12+\mathrm{log}({\rm{O}}/{\rm{H}})$ ∼ 8.2-8.7). We find no significant dependence of the IRX-β trend on environment. However, we find that at a given β, IRX is highly correlated with metallicity, and less correlated with mass, age, and specific star formation rate (sSFR). We conclude that, of the physical properties tested here, metallicity is the primary physical cause of the IRX-β scatter, and the IRX correlation with mass is presumably due to the mass dependence on metallicity. Our results indicate that the UV attenuation curve steepens with decreasing metallicity, and spans the full range of slope possibilities from a shallow Calzetti-type curve for galaxies with the highest metallicity in our sample ( $12+\mathrm{log}({\rm{O}}/{\rm{H}})$ ∼ 8.6) to a steep Small Magellanic Cloud (SMC)-like curve for those with $12+\mathrm{log}({\rm{O}}/{\rm{H}})$ ∼ 8.3. Using a Calzetti (SMC) curve for the low (high) metallicity galaxies can lead to up to a factor of 3 overestimation (underestimation) of the UV attenuation and obscured star formation rate. We speculate that this change is due to different properties of dust grains present in the interstellar medium of low- and high-metallicity galaxies. * Based on observations made with the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

Keywords: Interstellar dust, Galaxy chemical evolution, Galaxy properties, Chemical abundances, Interstellar dust extinction, Scaling relations, Galaxy abundances, Dust continuum emission, Galaxy evolution, Star formation
Solar-cycle-related Changes in the Helium Ionization Zones of the Sun. Helioseismic data for solar cycles 23 and 24 have shown unequivocally that solar dynamics changes with solar activity. Changes in solar structure have been more difficult to detect. Basu &amp; Mandel had claimed that the then-available data revealed changes in the He II ionization zone of the Sun. The amount of change, however, indicated the need for larger than expected changes in the magnetic fields. Now that helioseismic data spanning two solar cycles are available, we have redone the analysis using improved fitting techniques. We find that there is indeed a change in the region around the He II ionization zone that is correlated with activity. Because the data sets now cover two solar cycles, the time variation is easily discernible.

Keywords: Solar cycle, Solar interior, Helioseismology, Solar physics, Solar activity, Solar oscillations
Tightly Coupled Morpho-kinematic Evolution for Massive Star-forming and Quiescent Galaxies across 7 Gyr of Cosmic Time. We use the Fundamental Plane (FP) to measure the redshift evolution of the dynamical mass-to-light ratio (Mdyn/L) and the dynamical-to-stellar mass ratio (Mdyn/M*). Although conventionally used to study the properties of early-type galaxies, we here obtain stellar kinematic measurements from the Large Early Galaxy Astrophysics Census (LEGA-C) Survey for a sample of ∼1400 massive ( $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10.5$ ) galaxies at 0.6 &lt; z &lt; 1.0 that span a wide range in star formation activity. In line with previous studies, we find a strong evolution in Mdyn/Lg with redshift. In contrast, we find only a weak dependence of the mean value of Mdyn/M* on the specific star formation rate, and a redshift evolution that likely is explained by systematics. Therefore, we demonstrate that star-forming and quiescent galaxies lie on the same, stable mass FP across 0 &lt; z &lt; 1, and that the decrease in Mdyn/Lg toward high redshift can be attributed entirely to evolution of the stellar populations. Moreover, we show that the growth of galaxies in size and mass is constrained to occur within the mass FP. Our results imply either minimal structural evolution in massive galaxies since z ∼ 1, or a tight coupling in the evolution of their morphological and dynamical properties, and establish the mass FP as a tool for studying galaxy evolution with low impact from progenitor bias.

Keywords: Galaxy structure, Galaxy dynamics, Galaxy kinematics, Galaxy evolution
On the Presence of a Universal Acceleration Scale in Elliptical Galaxies. Dark matter phenomena in rotationally supported galaxies exhibit a characteristic acceleration scale of g† ≍ 1.2 × 10-10 m s-2. Whether this acceleration is a manifestation of a universal scale, or merely an emergent property with an intrinsic scatter, has been debated in the literature. Here we investigate whether a universal acceleration scale exists in dispersion-supported galaxies using two uniform sets of integral field spectroscopy (IFS) data from SDSS-IV MaNGA and ATLAS3D. We apply the spherical Jeans equation to 15 MaNGA and 4 ATLAS3D slow-rotator E0 (i.e., nearly spherical) galaxies. Velocity dispersion profiles for these galaxies are well determined with observational errors under control. Bayesian inference indicates that all 19 galaxies are consistent with a universal acceleration of ${g}_{\dagger }={1.5}_{-0.6}^{+0.9}\times {10}^{-10}$ m s-2. Moreover, all 387 data points from the radial bins of the velocity dispersion profiles are consistent with a universal relation between the radial acceleration traced by dynamics and that predicted by the observed distribution of baryons. This universality remains if we include 12 additional non-E0 slow-rotator elliptical galaxies from ATLAS ${}^{3{\rm{D}}}$ . Finally, the universal acceleration from MaNGA and ATLAS3D is consistent with that for rotationally supported galaxies, so our results support the view that dark matter phenomenology in galaxies involves a universal acceleration scale.

Keywords: Non-standard theories of gravity, Elliptical galaxies, Dark matter, Modified Newtonian dynamics
Magnetar Giant Flare Origin for GRB 200415A Inferred from a New Scaling Relation. Soft gamma-ray repeaters (SGRs) are a mainly Galactic population and originate from neutron stars with intense (B ≃ 1015 G) magnetic fields (magnetars). Occasionally, a giant flare occurs with enormous intensity, displaying a short, hard spike followed by a weaker, oscillatory phase that exhibits the rotational period of the neutron star. If the magnetar giant flares occur in nearby galaxies, they would appear as cosmic, short-hard gamma-ray bursts (GRBs) without detecting the weak oscillatory phase. Recently, a short-hard GRB named GRB 200415A was detected, with a position coincident with the Sculptor Galaxy (NGC 253), raising the question of whether it is a classic short GRB or a magnetar giant flare. Here we show that magnetar giant flares follow a scaling relation between the spectral peak energy and the isotropic energy in 1 keV-10 MeV, i.e., ${E}_{{\rm{p}}}\propto {E}_{\mathrm{iso}}^{1/4}$ , and locate in a distinct region of the Ep-Eiso plane from that of classic short GRBs. The relation can be well understood in the model that giant flares arise from the photosphere emissions of relativistically expanding fireballs. GRB 200415A, together with two other candidate giant flares (GRB 051103 and GRB 070201) follow this relation, which strongly favors the giant flare origin of these GRBs. The GeV emission detected by Fermi/LAT from GRB 200415A at 18-285 s can also be explained in the giant flare scenario. The total energy in the GeV emission implies a baryon load of ∼1023 g in the giant flare fireball of GRB 200415A.

Keywords: Magnetars, Gamma-ray bursts
Direct Radio Discovery of a Cold Brown Dwarf. Magnetospheric processes seen in gas giants such as aurorae and circularly polarized cyclotron maser radio emission have been detected from some brown dwarfs. However, previous radio observations targeted known brown dwarfs discovered via their infrared emission. Here we report the discovery of BDR J1750+3809, a circularly polarized radio source detected around 144 MHz with the Low-Frequency Array (LOFAR) telescope. Follow-up near-infrared photometry and spectroscopy show that BDR J1750+3809 is a cold methane dwarf of spectral type T6.5 ± 1 at a distance of ${65}_{-8}^{+9}\,\mathrm{pc}$ . The quasi-quiescent radio spectral luminosity of BDR J1750+3809 is ≍5 × 1015 erg s-1 Hz-1, which is over two orders of magnitude larger than that of the known population of comparable spectral type. This could be due to a preferential geometric alignment or an electrodynamic interaction with a close companion. In addition, as the emission is expected to occur close to the electron gyrofrequency, the magnetic field strength at the emitter site in BDR J1750+3809 is B ≳ 25 G, which is comparable to planetary-scale magnetic fields. Our discovery suggests that low-frequency radio surveys can be employed to discover substellar objects that are too cold to be detected in infrared surveys.

Keywords: Magnetospheric radio emissions, T dwarfs
A Framework for Multiphase Galactic Wind Launching Using TIGRESS. Galactic outflows have density, temperature, and velocity variations at least as large as those of the multiphase, turbulent interstellar medium (ISM) from which they originate. We have conducted a suite of parsec-resolution numerical simulations using the TIGRESS framework, in which outflows emerge as a consequence of interaction between supernovae (SNe) and the star-forming ISM. The outflowing gas is characterized by two distinct thermal phases, cool (T ≲ 104 K) and hot (T ≳ 106 K), with most mass carried by the cool phase and most energy and newly injected metals carried by the hot phase. Both components have a broad distribution of outflow velocity, and especially for cool gas this implies a varying fraction of escaping material depending on the halo potential. Informed by the TIGRESS results, we develop straightforward analytic formulae for the joint probability density functions (PDFs) of mass, momentum, energy, and metal loading as distributions in outflow velocity and sound speed. The model PDFs have only two parameters, star formation rate surface density ${{\rm{\Sigma }}}_{\mathrm{SFR}}$ and the metallicity of the ISM, and fully capture the behavior of the original TIGRESS simulation PDFs over ${{\rm{\Sigma }}}_{\mathrm{SFR}}\in ({10}^{-4},1)\,{M}_{\odot }\,{\mathrm{kpc}}^{-2}\,{\mathrm{yr}}^{-1}$ . Employing PDFs from resolved simulations will enable implementations of subgrid models for galaxy formation with wind velocity and temperature (as well as total loading factors) that are based on theoretical predictions rather than empirical tuning. This is a critical step to incorporate advances from TIGRESS and other high-resolution simulations in future cosmological hydrodynamics and semi-analytic galaxy formation models. We release a Python package to prototype our model and to ease its implementation.

Keywords: Galactic winds, Galaxy formation, Galaxy fountains, Stellar feedback, Galaxy winds
Methanimine as a Key Precursor of Imines in the Interstellar Medium: The Case of Propargylimine. A gas-phase formation route is proposed for the recently detected propargylimine molecule. In analogy to other imines, such as cyanomethanimine, the addition of a reactive radical (C2H in the present case) to methanimine (CH2NH) leads to reaction channels open also in the harsh conditions of the interstellar medium. Three possible isomers can be formed in the CH2NH + C2H reaction: Z- and E-propargylimine (Z-,E-PGIM) as well as N-ethynyl-methanimine (N-EMIM). For both PGIM species, the computed global rate coefficient is nearly constant in the 20-300 K temperature range, and of the order of 2-3 × 10-10 cm3 molecule-1 s-1, while that for N-EMIM is about two orders of magnitude smaller. Assuming equal destruction rates for the two isomers, these results imply an abundance ratio for PGIM of [Z]/[E] ∼ 1.5, which is only slightly underestimated with respect to the observational datum.

Keywords: Interstellar molecules, Interstellar abundances, Interstellar medium, Astrochemistry
A Precursor Balloon Mission for Venusian Astrobiology. The potential detection of phosphine in the atmosphere of Venus has reignited interest in the possibility of life aloft in this environment. If the cloud decks of Venus are indeed an abode of life, it should reside in the "habitable zone" between ∼50-60 km altitude, roughly coincident with the middle cloud deck, where the temperature and pressure (but not the atmospheric composition) are similar to conditions at the Earth's surface. We map out a precursor astrobiological mission to search for such putative lifeforms in situ with instrument balloons, which could be delivered to Venus via launch opportunities in 2022-2023. This mission would collect aerosol and dust samples by means of small balloons floating in the Venusian cloud deck and directly scrutinize whether they include any apparent biological materials and, if so, their shapes, sizes, and motility. Our balloon mission would also be equipped with a miniature mass spectrometer that should permit the detection of complex organic molecules. The mission is augmented by contextual cameras to search for macroscopic signatures of life in the Venusian atmospheric habitable zone. Finally, mass and power constraints permitting, radio interferometric determinations of the motion of the balloons in Venusian winds, together with in situ temperature and pressure measurements, will provide valuable insights into the poorly understood meteorology of the middle cloud region.

Keywords: Space vehicle instruments, Venus, Astrobiology, Biosignatures, Space vehicles
Radiogenic Heating and Its Influence on Rocky Planet Dynamos and Habitability. The thermal evolution of rocky planets on geological timescales (Gyr) depends on the heat input from the long-lived radiogenic elements potassium, thorium, and uranium. Concentrations of the latter two in rocky planet mantles are likely to vary by up to an order of magnitude between different planetary systems because Th and U, like other heavy r-process elements, are produced by rare stellar processes. Here we discuss the effects of these variations on the thermal evolution of an Earth-size planet, using a 1D parameterized convection model. Assuming Th and U abundances consistent with geochemical models of the Bulk Silicate Earth based on chondritic meteorites, we find that Earth had just enough radiogenic heating to maintain a persistent dynamo. According to this model, Earth-like planets of stars with higher abundances of heavy r-process elements, indicated by the relative abundance of europium in their spectra, are likely to have lacked a dynamo for a significant fraction of their lifetimes, with potentially negative consequences for hosting a biosphere. Because the qualitative outcomes of our 1D model are strongly dependent on the treatment of viscosity, further investigations using fully 3D convection models are desirable.

Keywords: Extrasolar rocky planets, R-process, Super Earths, Earth (planet), Exoplanet evolution, Astrobiology, Stellar nucleosynthesis, Magnetic fields
Fast Radio Burst Trains from Magnetar Oscillations. Quasi-periodic oscillations inferred during rare magnetar giant flare tails were initially interpreted as torsional oscillations of the neutron star (NS) crust, and have been more recently described as global core+crust perturbations. Similar frequencies are also present in high-signal-to-noise magnetar short bursts. In magnetars, disturbances of the field are strongly coupled to the NS crust regardless of the triggering mechanism of short bursts. For low-altitude magnetospheric magnetar models of fast radio bursts (FRBs) associated with magnetar short bursts, such as the low-twist model, crustal oscillations may be associated with additional radio bursts in the encompassing short burst event (as recently suggested for SGR 1935+2154). Given the large extragalactic volume probed by wide-field radio transient facilities, this offers the prospect of studying NS crusts leveraging samples far more numerous than galactic high-energy magnetar bursts by studying statistics of subburst structure or clustered trains of FRBs. We explore the prospects for distinguishing NS equation of state models with increasingly larger future sets of FRB observations. Lower l-number eigenmodes (corresponding to FRB time intervals of ∼5-50 ms) are likely less susceptible than high-l modes to confusion by systematic effects associated with the NS crust physics, magnetic field, and damping. They may be more promising in their utility, and also may corroborate models where FRBs arise from mature magnetars. Future observational characterization of such signals can also determine whether they can be employed as cosmological "standard oscillators" to constrain redshift, or can be used to constrain the mass of FRB-producing magnetars when reliable redshifts are available.

Keywords: Neutron stars, Cosmology, Neutron star cores, High energy astrophysics, Stellar oscillations, Soft gamma-ray repeaters, Radio bursts, Nuclear astrophysics, Non-thermal radiation sources, Magnetars, Asteroseismology, Radio transient sources
Discovery of Raman-scattered He II λ6545 in the Planetary Nebulae NGC 6886 and NGC 6881. Young planetary nebulae (PNe) retain a large amount of neutral material that was shed in the previous asymptotic giant branch stage. The thick H I region in young PNe can be effectively probed by illuminating far-UV radiation that may be inelastically scattered to appear in the optical region. Raman-scattered features are unique spectroscopic tracers of neutral regions that can be used to investigate the mass-loss process in young PNe. We conduct high-resolution spectroscopy of young PNe using the Bohyunsan Observatory Echelle Spectrograph (BOES) and report the discovery of a Raman-scattered He II feature at 6545 Å in NGC 6886 and NGC 6881. The Raman-scattered He II features have been found in only five PNe so far, and in particular, it is the first direct detection of an H I component in NGC 6881. The Raman He II λ6545 features in the two PNe are observed to be redshifted with respect to He II λ6560, indicating that the neutral regions are expanding. We perform line profile analyses using the grid-based Monte Carlo code "STaRS" by assuming a neutral hydrogen region in the shape of a partial spherical shell expanding radially. The profiles are well fitted with the model parameters of covering factor CF = 0.3, H I column density NHI = 5 × 1020 cm-2, and expansion speed ${v}_{\exp }=25\,\,\mathrm{km}\,{{\rm{s}}}^{-1}$ for NGC 6886 and CF = 0.6, NHI = 3 × 1020 cm-2, and ${v}_{\exp }=30\,\mathrm{km}\,{{\rm{s}}}^{-1}$ for NGC 6881, respectively.

Keywords: Planetary nebulae, H I regions, Stellar mass loss