Sazuna/UAT_keywords huggingface dataset:
Mixed-mode Ensemble Asteroseismology of Low-luminosity Kepler Red Giants. We present measurements of the dipole mode asymptotic period spacing (∆Π1), the coupling factor between the p- and g-modes (q), the g-mode phase offset (ϵ  g ), and the mixed-mode frequency rotational splitting (δ ν rot) for 1074 low-luminosity red giants from the Kepler mission. Using oscillation mode frequencies extracted from each star, we apply Bayesian optimization to estimate ∆Π1 from the power spectrum of the stretched-period spectrum and to perform the subsequent forward modeling of the mixed-mode frequencies. With our measurements, we show that the mode coupling factor q shows significant anticorrelation with both the stellar mass and metallicity, and can reveal highly metal-poor stars. We present the evolution of ϵ  g  up the lower giant branch up to before the luminosity bump, and find no significant trends in ϵ  g  or δ ν rot with the stellar mass and metallicity in our sample. Additionally, we identify six new red giants showing anomalous distortions in their g-mode pattern. Our data products, code, and results are provided in a public repository.

Keywords: Stellar oscillations, Asteroseismology, Astronomy data analysis, Stellar properties
Can Cuspy Dark-matter-dominated Halos Hold Cored Stellar Mass Distributions?. According to the current concordance cosmological model, dark matter (DM) particles are collisionless and produce self-gravitating structures with a central cusp, which, generally, is not observed. The observed density tends to a central plateau or core, explained within the cosmological model through the gravitational feedback of baryons on DM. This mechanism becomes inefficient when decreasing the galaxy's stellar mass so that in the low-mass regime (M ⋆ ≪ 106 M ⊙) the energy provided by the baryons is insufficient to modify cusps into cores. Thus, if cores exist in these galaxies they have to reflect departures from the collisionless nature of DM. Measuring the DM mass distribution in these faint galaxies is extremely challenging; however, their stellar mass distribution can be characterized through deep photometry. Here we provide a way of using only the stellar mass distribution to constrain the underlying DM distribution. The so-called Eddington inversion method allows us to discard pairs of stellar distributions and DM potentials requiring (unphysical) negative distribution functions in the phase space. In particular, cored stellar density profiles are incompatible with the Navarro-Frenk-White (NFW) potential expected from collisionless DM if the velocity distribution is isotropic and the system spherically symmetric. Through a case-by-case analysis, we are able to relax these assumptions to consider anisotropic velocity distributions and systems that do not have exact cores. In general, stellar distributions with radially biased orbits are difficult to reconcile with NFW-like potentials, and cores in the baryon distribution tend to require cores in the DM distribution.

Keywords: Galaxy dark matter halos, Theoretical techniques, Cold dark matter, Dwarf galaxies, Navarro-Frenk-White profile, Galaxy mass distribution, Low surface brightness galaxies
Limits on Fast Radio Burst-like Counterparts to Gamma-Ray Bursts Using CHIME/FRB. Fast radio bursts (FRBs) are a class of highly energetic, mostly extragalactic radio transients lasting for ~milliseconds. While over 600 FRBs have been published so far, their origins are presently unclear, with some theories for extragalactic FRBs predicting accompanying high-energy emission. In this work, we use the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst (CHIME/FRB) Project to explore whether any FRB-like radio emission coincides in space and time with 81 gamma-ray bursts (GRBs) detected between 2018 July 17 and 2019 July 8 by Swift/BAT and Fermi/GBM. We do not find any statistically significant coincident pairs within 3σ of each other's spatial localization regions and within a time difference of up to one week. In addition to searching for spatial matches between known FRBs and known GRBs, we use CHIME/FRB to constrain FRB-like (~1-10 ms) radio emission before, at the time of, or after the reported high-energy emission at the position of 39 GRBs. For short gamma-ray bursts (SGRBs), we constrain the radio flux in the 400-800 MHz band to be under a few kJy for ~5.5-12.5 hr post-high-energy burst. We use these limits to constrain models that predict FRB-like prompt radio emission after SGRBs. For long gamma-ray bursts, we constrain the radio flux to be under a few kJy from ~6 hr pre-high-energy burst to ~12 hr post-high-energy burst.

Keywords: Gamma-ray bursts, Gamma-ray bursters, Radio bursts, Radio astronomy, Radio transient sources
SN 2018gj: A Short Plateau Type II Supernova with Persistent Blueshifted Ha Emission. We present an extensive, panchromatic photometric (UV, optical, and near-IR) and low-resolution optical spectroscopic coverage of a Type IIP supernova SN 2018gj that occurred on the outskirts of the host galaxy NGC 6217. From the V-band light curve, we estimate the plateau length to be ~ 70 ± 2 days, placing it among the very few well-sampled short plateau supernovae (SNe). With V-band peak absolute magnitude M  V  ≤ -17.0 ± 0.1 mag, it falls in the middle of the luminosity distribution of the Type II SNe. The color evolution is typical to other Type II SNe except for an early elbow-like feature in the evolution of V - R color owing to its early transition from the plateau to the nebular phase. Using the expanding photospheric method, we present an independent estimate of the distance to SN 2018gj. We report the spectral evolution to be typical of a Type II SNe. However, we see a persistent blueshift in emission lines until the late nebular phase, not ordinarily observed in Type II SNe. The amount of radioactive nickel (56Ni) yield in the explosion was estimated to be 0.026 ± 0.007 M ☉. We infer from semianalytical modeling, nebular spectrum, and 1D hydrodynamical modeling that the probable progenitor was a red supergiant with a zero-age-main-sequence mass ≤13 M ☉. In the simulated hydrodynamical model light curves, reproducing the early optical bolometric light curve required an additional radiation source, which could be the interaction with the proximal circumstellar matter.

Keywords: Observational astronomy, Type II supernovae, Red supergiant stars, Hydrodynamical simulations
Estimators of Bolometric Luminosity and Black Hole Mass with Mid-infrared Continuum Luminosities for Dust-obscured Quasars: Prevalence of Dust-obscured SDSS Quasars. We present bolometric luminosity (L bol) and black hole (BH) mass (M BH) estimators based on mid-infrared (MIR) continuum luminosity (hereafter, L MIR) that are measured from infrared (IR) photometric data. The L MIR-based estimators are relatively immune from dust extinction effects, hence they can be used for dust-obscured quasars. To derive the L bol and M BH estimators, we use unobscured quasars selected from the Sloan Digital Sky Survey (SDSS) quasar catalog, which have wide ranges of L bol (1044.62-1046.16 erg s-1) and M BH (107.14-109.69 M ⊙). We find empirical relations between (i) continuum luminosity at 5100 Å (hereafter, L5100) and L MIR; (ii) L bol and L MIR. Using these relations, we derive the L MIR-based L bol and M BH estimators. We find that our estimators allow the determination of L bol and M BH at an accuracy of ~0.2 dex against the fiducial estimates based on the optical properties of the unobscured quasars. We apply the L MIR-based estimators to SDSS quasars at z ≲ 0.5 including obscured ones. The ratios of L bol from the L MIR-based estimators to those from the optical luminosity-based estimators become larger with the amount of the dust extinction, and a non-negligible fraction (~15%) of the SDSS quasars exhibits ratios greater than 1.5. This result suggests that dust extinction can significantly affect physical parameter derivations even for SDSS quasars, and that dust extinction needs to be carefully taken into account when deriving quasar properties.

Keywords: Supermassive black holes, Quasars, Infrared astronomy, Active galactic nuclei, Galaxy evolution
JWST/NIRSpec Balmer-line Measurements of Star Formation and Dust Attenuation at z   3-6. We present an analysis of the star formation rates (SFRs) and dust attenuation properties of star-forming galaxies at 2.7 ≤ z &lt; 6.5 drawn from the Cosmic Evolution Early Release Science Survey. Our analysis is based on JWST/NIRSpec Micro-Shutter Assembly R ~ 1000 spectroscopic observations covering approximately 1-5 μm. Our primary rest-frame optical spectroscopic measurements are Hα/Hβ Balmer decrements, which we use as an indicator of nebular dust attenuation. In turn, we use Balmer decrements to obtain dust-corrected Hα-based SFRs (i.e., SFR(Hα)). We construct the relationship between SFR(Hα) and stellar mass (M *) in three bins of redshift (2.7 ≤ z &lt; 4.0, 4.0 ≤ z &lt; 5.0, and 5.0 ≤ z &lt; 6.5), which represents the first time the star-forming main sequence has been traced at these redshifts using direct spectroscopic measurements of Balmer emission as a proxy for SFR. In tracing the relationship between SFR(Hα) and M * back to such early times (z &gt; 3), it is essential to use a conversion factor between Hα and SFR that accounts for the subsolar metallicity prevalent among distant galaxies. We also use measured Balmer decrements to investigate the relationship between dust attenuation and stellar mass out to z ~ 6. The lack of significant redshift evolution in attenuation at fixed stellar mass, previously confirmed using Balmer decrements out to z ~ 2.3, appears to hold out to z ~ 6.5. Given the rapidly evolving gas, dust, and metal content of star-forming galaxies at fixed mass, this lack of significant evolution in attenuation provides an ongoing challenge to explain.

Keywords: Galaxy formation, High-redshift galaxies, Galaxy evolution
Rapid Formation of Gas-giant Planets via Collisional Coagulation from Dust Grains to Planetary Cores. II. Dependence on Pebble Bulk Density and Disk Temperature. Thanks to "dust-to-planet" simulations (DTPSs), which treat the collisional evolution directly from dust to giant-planet cores in a protoplanetary disk, we showed that giant-planet cores are formed in ≲10 au in several 105 yr, because porous pebbles grow into planetesimals via collisions prior to drift in 10 au. However, such porous pebbles are unlikely to reproduce the polarized millimeter wavelength light observed from protoplanetary disks. We thus investigate gas-giant core formation with nonporous pebbles via DTPSs. Even nonporous bodies can grow into planetesimals and massive cores that are possible to be gas giants are also formed in several 105 yr. The rapid core formation is mainly via the accretion of planetesimals produced by collisional coagulation of pebbles drifting from the outer disk. The formation mechanism is similar to the case with porous pebbles, while core formation occurs in a wider region (5-10 au) than that with porous pebbles. Although pebble growth and core formation depend on the disk temperature, core formation is likely to occur with disk temperatures in typical optical thick disks around protostars.

Keywords: Protoplanetary disks, Planet formation
XMM-Newton Observations of Two Archival X-Ray Weak Type 1 Quasars: Obscuration Induced X-Ray Weakness and Variability. We report XMM-Newton observations of two examples of an unclassified type of X-ray weak quasars from the Pu et al. survey of X-ray weak quasars in the Chandra archive, SDSS J083116.62+321329.6 at z = 1.797 and SDSS J142339.87+042041.1 at z = 1.702. They do not belong to the known populations of X-ray weak quasars that show broad absorption lines, weak ultraviolet (UV) broad emission lines, or red optical/UV continua. Instead, they display typical quasar UV spectra and spectral energy distributions. In the XMM-Newton observations, both quasars show nominal levels of X-ray emission with typical quasar X-ray spectral shapes (power-law photon indices of ${1.99}_{-0.23}^{+0.27}$ and ${1.86}_{-0.14}^{+0.15}$ ), displaying strong X-ray variability compared to the archival Chandra data (variability factors of ${4.0}_{-1.4}^{+1.6}$ and ${9.0}_{-3.8}^{+7.4}$ in terms of the 2 keV flux density). Simultaneous optical (rest-frame UV) spectra indicate no strong variability compared to the archival spectra. Long-term optical/UV and infrared light curves do not show any substantial variability either. We consider that the X-ray weakness observed in the Chandra data is due to X-ray obscuration from a small-scale dust-free absorber, likely related to accretion-disk winds. Such X-ray weak/absorbed states are probably rare in typical quasars, and thus both targets recovered to X-ray nominal-strength states in the XMM-Newton observations.

Keywords: Active galaxies, X-ray active galactic nuclei, Galaxies, Quasars
The GMRT High Resolution Southern Sky Survey for Pulsars and Transients. VI. Discovery of Nulling, Localization, and Timing of PSR J1244-4708. Many pulsars in the known population exhibit nulling, which is characterized by a sudden cessation and subsequent restoration of radio emission. In this work, we present the localization, timing, and emission properties of a pulsar discovered by the GMRT High Resolution Southern Sky survey: J1244-4708. Moreover, we find that this pulsar shows nulling, with a nulling fraction close to 60%. A quasiperiodicity is also seen in the nulling from this pulsar with two timescales. We demonstrate the broadband nature of nulling in this pulsar using simultaneous observations in band-3 (300-500 MHz) and band-4 (550-750 MHz) with the upgraded GMRT. We also present a comparison of the efficiency of various search approaches such as single pulse search, fast folding algorithm (FFA)-based search, and fast Fourier transform-based search to search for nulling pulsars. We demonstrated that the FFA search is advantageous for detecting extreme nulling pulsars, which is also confirmed with multiple epochs of observations for the nulling pulsars using the GMRT.

Keywords: Observational astronomy, Astronomical techniques, Radio pulsars
Gravitational Wave Eigenfrequencies from Neutrino-driven Core-collapse Supernovae. Core-collapse supernovae (CCSNe) are predicted to produce gravitational waves (GWs) that may be detectable by Advanced LIGO/Virgo. These GW signals carry information from the heart of these cataclysmic events, where matter reaches nuclear densities. Recent studies have shown that it may be possible to infer the properties of the proto-neutron star (PNS) via GWs generated by hydrodynamic perturbations of the PNS. However, we lack a comprehensive understanding of how these relationships may change with the properties of CCSNe. In this work, we build a self-consistent suite of over 1000 exploding CCSNe from a grid of progenitor masses and metallicities combined with six different nuclear equations of state (EOS). Performing a linear perturbation analysis on each model, we compute the resonant GW frequencies of the PNS, and we motivate a time-agnostic method for identifying characteristic frequencies of the dominant GW emission. From this, we identify two characteristic frequencies, of the early- and late-time signal, that measure the surface gravity of the cold remnant neutron star, and simultaneously constrain the hot nuclear EOS. However, we find that the details of the CCSN model, such as the treatment of gravity or the neutrino transport, and whether it explodes, noticeably change the magnitude and evolution of the PNS eigenfrequencies.

Keywords: Neutron stars, Core-collapse supernovae, Gravitational wave sources, General relativity, Gravitational waves, LIGO
The El Gordo Galaxy Cluster Challenges ΛCDM for Any Plausible Collision Velocity. El Gordo (ACT-CL J0102-4915) is an extraordinarily large and bright galaxy cluster collision. In a previous study, we found that El Gordo is in 6.2σ tension with the Λ cold dark matter (ΛCDM) standard model when assuming the nominal mass and infall velocity values from the hydrodynamical simulations of Zhang et al. (M 200 = 3.2 × 1015 M ⊙ and V infall = 2500 km s-1, respectively). The recent weak-lensing study of Kim et al. showed that the mass of El Gordo is actually ${2.13}_{-0.23}^{+0.25}\times {10}^{15}{M}_{\odot }$ . Here we explore the level of tension between El Gordo and ΛCDM for the new mass estimate, assuming several V infall values. We find that in order to reduce the tension below the 5σ level, the El Gordo subclusters should have V infall &lt; 2300 km s-1 (V infall &lt; 1800 km s-1 when considering the combined tension with the Bullet Cluster). To the best of our knowledge, the El Gordo hydrodynamical simulations conducted so far require V infall ≥ 2500 km s-1 to simultaneously reproduce its morphology and its high X-ray luminosity and temperature. We therefore conclude that El Gordo still poses a significant challenge to ΛCDM cosmology. Whether the properties of El Gordo can be reconciled with a lower V infall should be tested with new hydrodynamical simulations that explore different configurations of the interaction.

Keywords: Galaxy clusters, Dark matter, Gravitation, Large-scale structure of the universe
Structure, Kinematics, and Observability of the Large Magellanic Cloud's Dynamical Friction Wake in Cold versus Fuzzy Dark Matter. The Large Magellanic Cloud (LMC) will induce a dynamical friction (DF) wake on infall to the Milky Way (MW). The MW's stellar halo will respond to the gravity of the LMC and the dark matter (DM) wake, forming a stellar counterpart to the DM wake. This provides a novel opportunity to constrain the properties of the DM particle. We present a suite of high-resolution, windtunnel-style simulations of the LMC's DF wake that compare the structure, kinematics, and stellar tracer response of the DM wake in cold DM (CDM), with and without self-gravity, versus fuzzy DM (FDM) with m  a  = 10-23 eV. We conclude that the self-gravity of the DM wake cannot be ignored. Its inclusion raises the wake's density by ~10%, and holds the wake together over larger distances (~50 kpc) than if self-gravity is ignored. The DM wake's mass is comparable to the LMC's infall mass, meaning the DM wake is a significant perturber to the dynamics of MW halo tracers. An FDM wake is more granular in structure and is ~20% dynamically colder than a CDM wake, but with comparable density. The granularity of an FDM wake increases the stars' kinematic response at the percent level compared to CDM, providing a possible avenue of distinguishing a CDM versus FDM wake. This underscores the need for kinematic measurements of stars in the stellar halo at distances of 70-100 kpc.

Keywords: Milky Way dark matter halo, Cold dark matter, Milky Way dynamics, Large Magellanic Cloud, Milky Way stellar halo, Dynamical friction
Modeling the Central Supermassive Black Hole Mass of Quasars via the LSTM Approach. One of the fundamental questions about quasars is related to their central supermassive black holes. The reason for the existence of these black holes with such a huge mass is still unclear, and various models have been proposed to explain them. However, there is still no comprehensive explanation that is accepted by the community. The only thing we are sure of is that these black holes were not created by the collapse of giant stars or the accretion of matter around them. Moreover, another important question is related to the mass distribution of these black holes over time. Observations have shown that if we go back through redshift, we see black holes with more mass, and after passing the peak of star formation redshift, this procedure decreases. Nevertheless, the exact redshift of this peak is still controversial. In this paper, with the help of deep learning and the LSTM algorithm, we try to find a suitable model for the mass of the central black holes of quasars over time by considering both the QUOTAS and QuasarNET data sets. Our model was built with these data reported from redshift 3 to 7 and for two redshift intervals, 0-3 and 7-10, and it predicted the mass of the quasars' central supermassive black holes. We have also tested our model for the specified intervals with observed data from central black holes and discussed the results.

Keywords: Quasars
DiskMINT: A Tool to Estimate Disk Masses with CO Isotopologues. CO is one of the most abundant molecules in protoplanetary disks, and optically thin emission from its isotopologues has been detected in many of them. However, several past works have argued that reproducing the relatively low emission of CO isotopologues requires a very low disk mass or significant CO depletion. Here, we present a Python code, DiskMINT, which includes gas density and temperature structures that are both consistent with the thermal pressure gradient, isotope-selective chemistry, and conversion of CO into CO2 ice on grain surfaces. The code generates a self-consistent disk structure, where the gas disk distribution is obtained from a spectral energy distribution (SED)-derived dust disk structure with multiple grain sizes. We use DiskMINT to study the disk of RU Lup, a high-accreting star whose disk was previously inferred to have a gas mass of only ~1.5 × 10-3 M ⊙ and gas-to-dust mass ratio of ~4. Our best-fit model to the long-wavelength continuum emission can explain the total C18O luminosity as well as the C18O velocity and radial intensity profiles, and it obtains a gas mass of ~1.2 × 10-2 M ⊙, an order of magnitude higher than previous results. A disk model with parametric Gaussian vertical distribution that better matches the IR SED can also explain the observables above with a similarly high gas mass ~2.1 × 10-2 M ⊙. We confirm the conclusions of Ruaud et al. that optically thin C18O rotational lines provide reasonable estimates of the disk mass and can therefore be used as gas disk tracers.

Keywords: Chemical abundances, Astrochemistry, Protoplanetary disks, CO line emission, Planet formation
Successive Energy Conversion at a Stepwise Dipolarization Front. Dipolarization fronts (DFs), ion-scale magnetic structures characterized by sharp enhancement of northward magnetic field developed within plasma jets, have been suggested to play a crucial role in the energy transfer chain in the terrestrial magnetotail. Here we present the first observation of successive energy conversion driven by multiple current layers at a stepwise DF, using high-cadence measurements from NASA's Magnetospheric Multiscale mission. The multiple current layers are adjacent and cause gradual variations of particles and electromagnetic fields, leading to an intense, successive increase of energy conversion rates at the DF in the satellite frame, with electromagnetic field energy being transformed into particle energy. The energy conversion is contributed by both ion and electron currents. The motional electric field drives the energy conversion, while the wave electric field fed by lower hybrid drift instability modulates the energy partition. These results provide new insights into understanding energy transfer in the terrestrial magnetotail.

Keywords: Space plasmas