Sazuna/UAT_keywords huggingface dataset:
X-Ray Emission from Star-cluster Winds in Starburst Galaxies. Inspired by the excess soft X-ray emission recently detected in Green Pea galaxies, we model the soft X-ray emission (0.5-2.0 keV) of hot gas from star-cluster winds. By combining individual star clusters, we estimate the soft X-ray emission expected from the typically unresolved diffuse hot gas in starburst galaxies, devoid of competing emission from, e.g., active galactic nuclei (AGNs) or other unresolved point sources. We use stellar models of subsolar metallicities (0.02 Z ⊙ and 0.4 Z ⊙) and take into account supernova explosions for massive stars. For lower metallicities, we find that stellar winds do not contribute significantly (≲3% of the mechanical energy) to the observed soft X-ray emission of normal star-forming galaxies. For higher metallicities and possibly also for larger proportions of massive star clusters in the simulated starburst galaxies, we reproduce well the observed correlation between star formation rate and X-ray luminosity previously reported in the literature. However, we find that no combination of model assumptions is capable of reproducing the substantial soft X-ray emission observed from Green Pea galaxies, indicating that other emission mechanisms (i.e., unusually large quantities of high-/low-mass X-ray binaries, ultraluminous X-ray sources, a modified initial mass function, intermediate-mass black holes, or AGNs) are more likely to be responsible for the X-ray excess.

Keywords: X-ray astronomy, Starburst galaxies, Hydrodynamical simulations, Compact dwarf galaxies, Stellar winds, Astronomical simulations
Methanol Mapping in Cold Cores: Testing Model Predictions. Chemical models predict that in cold cores gas-phase methanol is expected to be abundant at the outer edge of the CO depletion zone, where CO is actively adsorbed. CO adsorption correlates with volume density in cold cores, and, in nearby molecular clouds, catastrophic CO freeze-out happens at volume densities above 104 cm-3. The methanol production rate is maximized there and its freeze-out rate does not overcome its production rate, while the molecules are shielded from UV destruction by gas and dust. Thus, in cold cores, methanol abundance should generally correlate with visual extinction, which depends on both volume and column density. In this work, we test the most basic model prediction that maximum methanol abundance is associated with a local A  V  ~ 4 mag in dense cores and constrain the model parameters with the observational data. With the IRAM 30 m antenna, we mapped the CH3OH (2-1) and (3-2) transitions toward seven dense cores in the L1495 filament in Taurus to measure the methanol abundance. We use the Herschel/SPIRE maps to estimate visual extinction, and the C18O(2-1) maps from Tafalla &amp; Hacar to estimate CO depletion. We explored the observed and modeled correlations between the methanol abundances, CO depletion, and visual extinction, varying the key model parameters. The modeling results show that hydrogen surface diffusion via tunneling is crucial to reproduce the observed methanol abundances, and the necessary reactive desorption efficiency matches the one deduced from laboratory experiments. * This work is based on observations carried out under projects 013-18, 125-18, and 031-19 with the IRAM 30 m telescope. Institut de Radioastronomie Millimétrique (IRAM) is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Keywords: Interstellar molecules, Star forming regions, Astrochemistry, Submillimeter astronomy
Multiwavelength Variability Power Spectrum Analysis of the Blazars 3C 279 and PKS 1510-089 on Multiple Timescales. We present the results of variability power spectral density (PSD) analysis using multiwavelength radio to GeV γ-ray light curves covering timescales of decades/years to days/minutes for the blazars 3C 279 and PKS 1510-089. The PSDs are modeled as single power laws, and the best-fit spectral shape is derived using the "power spectral response" method. With more than 10 yr of data obtained with weekly/daily sampling intervals, most of the PSDs cover ~2-4 decades in temporal frequency; moreover, in the optical band, the PSDs cover ~6 decades for 3C 279 due to the availability of intranight light curves. Our main results are the following: (1) on timescales ranging from decades to days, the synchrotron and the inverse-Compton spectral components, in general, exhibit red-noise (slope ~2) and flicker-noise (slope ~1) type variability, respectively; (2) the slopes of γ-ray variability PSDs obtained using a 3 hr integration bin and 3 weeks total duration exhibit a range between ~1.4 and ~2.0 (mean slope = 1.60 ± 0.70), consistent within errors with the slope on longer timescales; (3) comparisons of fractional variability indicate more power on timescales ≤100 days at γ-ray frequencies compared to longer wavelengths, in general (except between the γ-ray and optical wavelengths for PKS 1510-089); (4) the normalization of intranight optical PSDs for 3C 279 appears to be a simple extrapolation from longer timescales, indicating a continuous (single) process driving the variability at optical wavelengths; and (5) the emission at optical/infrared wavelengths may involve a combination of disk and jet processes for PKS 1510-089.

Keywords: Blazars, Active galactic nuclei, Galaxy jets
Discovery, Timing, and Multiwavelength Observations of the Black Widow Millisecond Pulsar PSR J1555-2908. We report the discovery of PSR J1555-2908, a 1.79 ms radio and gamma-ray pulsar in a 5.6 hr binary system with a minimum companion mass of 0.052 M ⊙. This fast and energetic ( $\dot{E}=3\times {10}^{35}$ erg s-1) millisecond pulsar was first detected as a gamma-ray point source in Fermi Large Area Telescope (LAT) sky survey observations. Guided by a steep-spectrum radio point source in the Fermi error region, we performed a search at 820 MHz with the Green Bank Telescope that first discovered the pulsations. The initial radio pulse timing observations provided enough information to seed a search for gamma-ray pulsations in the LAT data, from which we derive a timing solution valid for the full Fermi mission. In addition to the discovery and timing of radio and gamma-ray pulsations, we searched for X-ray pulsations using NICER but no significant pulsations were detected. We also obtained time-series r-band photometry that indicates strong heating of the companion star by the pulsar wind. Material blown off the heated companion eclipses the 820 MHz radio pulse during inferior conjunction of the companion for ≈10% of the orbit, which is twice the angle subtended by its Roche lobe in an edge-on system.

Keywords: Millisecond pulsars, Gamma-ray sources, Compact binary stars, Pulsars, Binary pulsars, Radio pulsars
The Origin of Exponential Star-forming Disks. The disk components of galaxies generally show an exponential profile extending over several scale lengths, both in mass and star formation rate, but the physical origin is not well understood. We explore a physical model in which the galactic gas disk is viewed as a "modified accretion disk" in which coplanar gas inflow, driven by viscous stresses in the disk, provides the fuel for star formation, which progressively removes gas as it flows inward. We show that magnetic stresses from magneto-rotational instability are the most plausible source of the required viscosity, and construct a simple physical model to explore this. A key feature is to link the magnetic field strength to the local star formation surface density, ${B}_{\mathrm{tot}}\propto {{\rm{\Sigma }}}_{\mathrm{SFR}}^{\alpha }$ . This provides a feedback loop between star formation and the flow of gas. We find that the model naturally produces stable steady-state exponential disks, as long as α ~ 0.15, the value indicated from spatially resolved observations of nearby galaxies. The disk scale length h R is set by the rate at which the disk is fed, by the normalization of the B tot-ΣSFR relation and by the circular velocity of the halo. The angular momentum distribution of the gas and stars within the disk is a consequence of the transfer of angular momentum that is inherent to the operation of an accretion disk, rather than the initial angular momentum of the inflowing material. We suggest that magnetic stresses likely play a major role in establishing the stable exponential form of galactic disks.

Keywords: Galaxy magnetic fields, Galaxy formation, Galaxy structure, Galaxies
ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): A Hot Corino Survey toward Protostellar Cores in the Orion Cloud. The presence of complex organic molecules (COMs) in the interstellar medium is of great interest since it may link to the origin and prevalence of life in the universe. Aiming to investigate the occurrence of COMs and their possible origins, we conducted a chemical census toward a sample of protostellar cores as part of the Atacama Large Millimeter/submillimeter Array Survey of Orion Planck Galactic Cold Clumps project. We report the detection of 11 hot corino sources, which exhibit compact emissions from warm and abundant COMs, among 56 Class 0/I protostellar cores. All of the hot corino sources discovered are likely Class 0, and their sizes of the warm region (&gt;100 K) are comparable to 100 au. The luminosity of the hot corino sources exhibits positive correlations with the total number of methanol and the extent of its emissions. Such correlations are consistent with the thermal desorption picture for the presence of hot corinos and suggest that the lower-luminosity (Class 0) sources likely have a smaller region with COM emissions. With the same sample selection method and detection criteria being applied, the detection rates of the warm methanol in the Orion cloud (15/37) and the Perseus cloud (28/50) are statistically similar when the cloud distances and the limited sample size are considered. Observing the same set of COM transitions will bring a more informative comparison between the cloud properties.

Keywords: Interstellar molecules, Star forming regions, Astrochemistry, Low mass stars, Protostars
Recovery of TESS Stellar Rotation Periods Using Deep Learning. We used a convolutional neural network to infer stellar rotation periods from a set of synthetic light curves simulated with realistic spot-evolution patterns. We convolved these simulated light curves with real TESS light curves containing minimal intrinsic astrophysical variability to allow the network to learn TESS systematics and estimate rotation periods despite them. In addition to periods, we predict uncertainties via heteroskedastic regression to estimate the credibility of the period predictions. In the most credible half of the test data, we recover 10% accurate periods for 46% of the targets, and 20% accurate periods for 69% of the targets. Using our trained network, we successfully recover periods of real stars with literature rotation measurements, even past the 13.7 day limit generally encountered by TESS rotation searches using conventional period-finding techniques. Our method also demonstrates resistance to half-period aliases. We present the neural network and simulated training data, and introduce the software butterpy used to synthesize the light curves using realistic starspot evolution.

Keywords: Starspots, Computational astronomy, Stellar properties, Light curves, Convolutional neural networks, Stellar physics, Stellar rotation, Astronomical simulations
Comparison between Core-collapse Supernova Nucleosynthesis and Meteoric Stardust Grains: Investigating Magnesium, Aluminium, and Chromium. Isotope variations of nucleosynthetic origin among solar system solid samples are well documented, yet the origin of these variations is still uncertain. The observed variability of 54Cr among materials formed in different regions of the protoplanetary disk has been attributed to variable amounts of presolar, chromium-rich oxide (chromite) grains, which exist within the meteoritic stardust inventory and most likely originated from some type of supernova explosion. To investigate if core-collapse supernovae (CCSNe) could be the site of origin of these grains, we analyze yields of CCSN models of stars with initial masses 15, 20, and 25 M ⊙, and solar metallicity. We present an extensive abundance data set of the Cr, Mg, and Al isotopes as a function of enclosed mass. We find cases in which the explosive C ashes produce a composition in good agreement with the observed 54Cr/52Cr and 53Cr/52Cr ratios as well as the 50Cr/52Cr ratios. Taking into account that the signal at atomic mass 50 could also originate from 50Ti, the ashes of explosive He burning also match the observed ratios. Addition of material from the He ashes (enriched in Al and Cr relative to Mg to simulate the make-up of chromite grains) to the solar system's composition may reproduce the observed correlation between Mg and Cr anomalies, while material from the C ashes does not present significant Mg anomalies together with Cr isotopic variations. In all cases, nonradiogenic, stable Mg isotope variations dominate over the variations expected from 26Al.

Keywords: Explosive nucleosynthesis, Nucleosynthesis, Core-collapse supernovae, Stellar astronomy, Meteors, Interstellar medium, Meteorites, Stellar nucleosynthesis
GeV γ-Ray Emission of Compact Steep-spectrum Source 4C +39.23B. Thirteen yr observation data of 4FGL J0824.9+3915 with the Large Area Telescope on board the Fermi Gamma Ray Space Telescope (Fermi/LAT) are analyzed for revisiting whether 4C +39.23B, a compact steep-spectrum (CSS) source close to a flat-spectrum radio quasar (FSRQ) 4C +39.23A in the γ-ray emitting region of 4FGL J0824.9+3915, is a γ-ray emitter. We find that the time-integrated γ-ray emission of 4FGL J0824.9+3915 is overwhelmingly dominated by 4C +39.23A. It shows significant variability at a 6.7σ confidence level and the average γ-ray flux in the 0.1-300 GeV energy band is (1.60 ± 0.15) × 10-8 ph cm-2 s-1 with a power-law photon spectral index of 2.48 ± 0.05. During MJD 57500-58500, 4FGL J0824.9+3915 is in a low state with a steady γ-ray flux. Through the analysis of the Fermi/LAT observation data in this time interval, it is found that the test statistic values of the γ-ray emission from 4C +39.23A and 4C +39.23B are ~5 and ~31, respectively, indicating that the γ-ray emission in this time interval is dominated by CSS 4C +39.23B. The derived average flux in this time interval for 4C +39.23B is (9.40 ± 4.10) × 10-9 ph cm -2 s-1 with Γ γ  = 2.45 ± 0.17. Attributing the spectral energy distribution (SED) of 4C +39.23B to the radiations from its core and extended region, we show that the SED can be represented with a two-zone leptonic model. Its γ-ray emission is contributed to by the core region. The derived magnetic field strength and Doppler boosting factor of the core are 0.13 G and 6.5. Comparing 4C +39.23B with other γ-emitting CSSs and compact symmetric objects (CSOs) in the Γ γ  - L  γ  plane, it resembles CSSs.

Keywords: Non-thermal radiation sources, Relativistic jets, Active galactic nuclei
Revealing the Field Sub-subgiant Population Using a Catalog of Active Giant Stars and Gaia EDR3. Sub-subgiant stars (SSGs) fall below the subgiant branch and/or red of the giant branch in open and globular clusters, an area of the color-magnitude diagram (CMD) not populated by standard stellar evolution tracks. One hypothesis is that SSGs result from rapid rotation in subgiants or giants due to tidal synchronization in a close binary. The strong magnetic fields generated inhibit convection, which in turn produces large starspots, radius inflation, and lower-than-expected average surface temperatures and luminosities. Here we cross-reference a catalog of active giant binaries (RS CVns) in the field with Gaia EDR3. Using the Gaia photometry and parallaxes, we precisely position the RS CVns in a CMD. We identify stars that fall below a 14 Gyr, metal-rich isochrone as candidate field SSGs. Out of a sample of 1723 RS CVn, we find 448 SSG candidates, a dramatic expansion from the 65 SSGs previously known. Most SSGs have rotation periods of 2-20 days, with the highest SSG fraction found among RS CVn with the shortest periods. The ubiquity of SSGs among this population indicates that SSGs are a normal phase in evolution for RS CVn-type systems, not rare by-products of dynamical encounters found only in dense star clusters as some have suggested. We present our catalog of 1723 active giants, including Gaia photometry and astrometry, and rotation periods from the Transiting Exoplanet Survey Satellite and International Variable Star Index (VSX). This catalog can serve as an important sample to study the impacts of magnetic fields in evolved stars.

Keywords: Starspots, Stellar magnetic fields, Stellar activity, Stellar physics, Red giant stars, Red straggler stars
On the Energy Source of Ultrastripped Supernovae. Ultrastripped supernovae (USSNe) with a relatively low ejecta mass of ~0.1 M ⊙ (e.g., iPTF 14gqr and SN 2019dge) are considered to originate from ultrastripped carbon-oxygen cores in close binary systems and are likely to be progenitors of binary neutron stars. Here we conduct the explosion simulations of ultrastripped progenitors with various masses (1.45 M ⊙ ≤ M CO ≤ 2.0 M ⊙) based on results of neutrino-radiation hydrodynamics simulations, and consistently calculate the nucleosynthesis and the supernova light curves. We find that a USSN from a more massive progenitor has a larger ejecta mass but a smaller 56Ni mass mainly due to the fallback that leads to the light curve being dimmer and slower. By comparing the synthetic light curves with the observed ones, we show that SN 2019dge can be solely powered by 56Ni synthesized during the explosion of a progenitor with M CO ≲ 1.6 M ⊙ while iPTF 14gqr cannot be explained by the 56Ni-powered model; ~0.05 M ⊙ of 56Ni inferred from the light-curve fitting is argued to be difficult to synthesize for ultrastripped progenitors. We consider fallback accretion onto and rotation-powered relativistic wind from the newborn neutron star (NS) as alternative energy sources and show that iPTF 14gqr could be powered by a newborn NS with a magnetic field of B  p  ~ 1015 G and an initial rotation period of P  i  ~ 0.1 s.

Keywords: Explosive nucleosynthesis, Binary stars, Nucleosynthesis, Supernova dynamics, Close binary stars, Supernovae
Luminosity Function and Event Rate Density of XMM-Newton-selected Supernova Shock Breakout Candidates. A dozen X-ray supernova shock breakout (SN SBO) candidates were reported recently based on XMM-Newton archival data, which increased the X-ray-selected SN SBO sample by an order of magnitude. Assuming that they are genuine SN SBOs, we study the luminosity function (LF) by improving on the method used in our previous work. The light curves and the spectra of the candidates were used to derive the maximum volume within which these objects could be detected with XMM-Newton by simulation. The results show that the SN SBO LF can be described by either a broken power law (BPL) with indices (at the 68% confidence level) of 0.48 ± 0.28 and 2.11 ± 1.27 before and after the break luminosity at $\mathrm{log}({L}_{b}/\mathrm{erg}\,{{\rm{s}}}^{-1})$ = 45.32 ± 0.55 or a single power law (SPL) with an index of 0.80 ± 0.16. The local event rate densities of SN SBOs above 5 × 1042 erg s-1 are consistent for two models, i.e., ${4.6}_{-1.3}^{+1.7}\times {10}^{4}$ Gpc-3 yr-1 and ${4.9}_{-1.4}^{+1.9}\times {10}^{4}$ Gpc-3 yr-1 for BPL and SPL models, respectively. The number of fast X-ray transients of SN SBO origin can be significantly increased by wide-field X-ray telescopes such as the Einstein Probe.

Keywords: Luminosity function, X-ray transient sources, Time domain astronomy, Core-collapse supernovae
Unveiling the Origin of the Fermi Bubbles with MeV Photon Telescopes. The Fermi Bubbles (FBs) are a pair of large-scale ellipsoidal structures extending above and below the Galactic plane almost symmetrically aligned with the Galactic center. After more than 10 yr since their discovery, their nature and origin remain unclear. Unveiling the primary emission mechanisms, whether hadronic or leptonic, is considered to be the main tool to shed light on the topic. We explore the potential key role of MeV observations of the FB, and we provide a recipe to determine the sensitivity of Compton and Compton-pair telescopes to the extended emission of the FB. We illustrate the capabilities of the Imaging Compton Telescope COMPTEL, the newly selected NASA MeV mission Compton Spectrometer and Imager, as well as the expectations for a potential future Compton-pair telescope such as the All-sky Medium Energy Gamma-ray Observatory eXplorer.

Keywords: Gamma-rays, Stellar wind bubbles, Gamma-ray telescopes
Dust Mass Associated with the Supernova Remnant IC 443 When Emission Meets Extinction. The dust mass of the well-known supernova remnant IC 443 is estimated from both the infrared emission and the visual extinction. With photometry to the images taken by Spitzer, WISE, IRAS, AKARI, and Planck, the spectral energy distribution (SED) of the dust is obtained after subtracting synchrotron radiation and considering the spectral line emission. The dust mass is derived by fitting the SED with a two-component model, which results in a warm component with a temperature of ~53 K and mass of 0.1 M ⊙ and a cold component with a temperature of ~17 K and mass of 46 M ⊙. On the other hand, the dust mass is derived to be ~66 M ⊙ from the visual extinction of IC 443, which is identified from the 3D Bayestar extinction map and its coincidence with the infrared emission morphology. The dust mass derived from the infrared emission is in rough agreement with that derived from extinction. However, the two can be adjusted to be more consistent by using a different dust opacity or by considering optically thick radiation. In addition, the distribution of dust temperature and mass is analyzed by fitting the SED pixel-by-pixel.

Keywords: Supernova remnants, Interstellar dust, Dust continuum emission, Interstellar extinction
WISE View of Changing-look Active Galactic Nuclei: Evidence for a Transitional Stage of AGNs. The discovery of changing-look active galactic nuclei (CLAGNs) with a significant change in optical broad emission lines (optical CLAGNs) and/or strong variation of line-of-sight column densities (X-ray CLAGNs) challenges the orientation-based AGN unification model. We explore mid-infrared (mid-IR) properties for a sample of 57 optical CLAGNs and 11 X-ray CLAGNs based on the Wide-field Infrared Survey Explorer archive data. We find that Eddington-scaled mid-IR luminosities of both optical and X-ray CLAGNs stay just between those of low-luminosity AGNs and luminous QSOs. The average Eddington-scaled mid-IR luminosities for optical and X-ray CLAGNs are ~0.4% and ~0.5%, respectively, which roughly correspond to the bolometric luminosity of transition between a radiatively inefficient accretion flow and a Shakura-Sunyaev disk. We estimate the time lags of the variation in the mid-IR behind that in the optical band for 13 CLAGNs with strong mid-IR variability, where the tight correlation between the time lag and the bolometric luminosity (τ-L) for CLAGNs roughly follows that found in the luminous QSOs.

Keywords: Quasars, Reverberation mapping, LINER galaxies, Seyfert galaxies, Active galactic nuclei