Sazuna/UAT_keywords huggingface dataset:
Impact of a Magnetic Field on Neutrino-Matter Interactions in Core-collapse Supernovae. We explore the impact of a magnetic field on neutrino-matter interactions in core-collapse supernovae. We first derive the modified source terms for neutrino-nucleon scattering and neutrino absorption and emission processes in the moment formalism. Then, we perform full relativistic, three-dimensional, magnetorotational core-collapse supernova simulations of a $20\,{M}_{\odot }$ star with spectral neutrino transport. Our simulations self-consistently treat the parity-violation effects of weak interaction in the presence of an external magnetic field. The result shows significant global asymmetry, mostly confined in the proto-neutron star, clearly reflecting the magnetic field structure. The asymmetric property arises from two factors: the angle between the neutrino flux and magnetic field, and the term that is parallel to the magnetic field and is also proportional to the deviation of the distribution function of neutrinos from thermal equilibrium. The typical correction value amounts to ∼1% relative to the total neutrino-matter interaction rate for the magnetic field strength of $\sim {10}^{15\mbox{--}16}$ G. Although these asymmetric properties do not immediately affect the explosion dynamics, our results imply that they would be significant once the neutrinos diffuse out of the proto-neutron- star core carrying those asymmetries away. We also show that, during our simulation time of ∼370 ms after bounce, our results indicate that the correction value due to the modified inelastic scattering process dominates over that of the modified neutrino absorption and emission process.

Keywords: Supernova neutrinos, Radiative magnetohydrodynamics, Core-collapse supernovae, Supernova dynamics, Magnetohydrodynamical simulations
Estimation of the Galaxy Quenching Rate in the Illustris Simulation. Quenching is a key topic in exploring the formation and evolution of galaxies. In this work, we study the quenching rate, i.e., the variation in the fraction of quenched galaxies per unit time, of the Illustris-1 simulation. By building the quenched fraction function f(m, ρ, t) of each snapshot in the simulation, we derive an accurate form of quenching rate as ${{\mathfrak{R}}}_{q}={df}(m,\rho ,t)/{dt}$ . According to the analytic expression of the quenching rate ${{\mathfrak{R}}}_{q}$ , we split it into four components: mass quenching, environmental quenching, intrinsic mass quenching, and intrinsic environmental quenching. The precise value and evolutions can be given via the formula of ${{\mathfrak{R}}}_{q}$ . With this method, we analyze the Illustris-1 simulation. We find that quenched galaxies concentrate around M* ≃ 1011 h-1 M⊙ and δ + 1 ≃ 103.5 at earlier times and that the quenching galaxy population slowly shifts to lower stellar mass and lower overdensity regions with time. We also find that mass quenching dominates the quenching process in this simulation, in agreement with some previous analytical models. Intrinsic quenching is the second most important component. Environmental quenching is very weak, because it is possible that the pre- or post-processing of environments disguises environmental quenching as intrinsic quenching. We find that our method roughly predicts the actual quenching rate. It could well predict the actual number of galaxies quenched by intrinsic quenching. However, it overestimates the amount of mass quenching galaxies and underestimates the amount of environmental quenching. We suggest that the reason is the nonlinearity of the environmental overdensity change and mass growth of the galaxy.

Keywords: Hydrodynamical simulations, Galaxy formation, Galaxy quenching
Cycle-StarNet: Bridging the Gap between Theory and Data by Leveraging Large Data Sets. Advancements in stellar spectroscopy data acquisition have made it necessary to accomplish similar improvements in efficient data analysis techniques. Current automated methods for analyzing spectra are either (a) data driven, which requires prior knowledge of stellar parameters and elemental abundances, or (b) based on theoretical synthetic models that are susceptible to the gap between theory and practice. In this study, we present a hybrid generative domain-adaptation method that turns simulated stellar spectra into realistic spectra by applying unsupervised learning to large spectroscopic surveys. We apply our technique to the APOGEE H-band spectra at R = 22,500 and the Kurucz synthetic models. As a proof of concept, two case studies are presented. The first is the calibration of synthetic data to become consistent with observations. To accomplish this, synthetic models are morphed into spectra that resemble observations, thereby reducing the gap between theory and observations. Fitting the observed spectra shows an improved average ${\chi }_{R}^{2}$ reduced from 1.97 to 1.22, along with a mean residual reduced from 0.16 to -0.01 in normalized flux. The second case study is the identification of the elemental source of missing spectral lines in the synthetic modeling. A mock data set is used to show that absorption lines can be recovered when they are absent in one of the domains. This method can be applied to other fields that use large data sets and are currently limited by modeling accuracy. The code used in this study is made publicly available on GitHub (https://github.com/teaghan/Cycle_SN).

Keywords: Spectral line identification, Computational methods, Spectroscopy, Neural networks
Hadronic X-Ray Flares from Blazars. The detection of a high-energy neutrino from the flaring blazar TXS 0506+056 and the subsequent discovery of a neutrino excess from the same direction have strengthened the hypothesis that blazars are cosmic neutrino sources. The lack, however, of γ-ray flaring activity during the latter period challenges the standard scenario of correlated γ-ray and high-energy neutrino emission in blazars. We propose instead that TeV-PeV neutrinos are produced in coincidence with X-ray flares that are powered by proton synchrotron radiation. In this case, neutrinos are produced by photomeson interactions of protons with their own synchrotron radiation, while MeV to GeV γ-rays are the result of synchrotron-dominated electromagnetic cascades developed in the source. Using a time-dependent approach, we find that this "pure hadronic flaring" hypothesis has several interesting consequences. The X-ray flux is a good proxy for the all-flavor neutrino flux, while certain neutrino-rich X-ray flares may be dark in GeV-TeV γ-rays. Lastly, hadronic X-ray flares are accompanied by an equally bright MeV component that is detectable by proposed missions like e-ASTROGAM and AMEGO. We applied this scenario to the extreme blazar 3HSP J095507.9+355101 which has been associated with IceCube-200107A while undergoing an X-ray flare. We showed that the number of muon and anti-muon neutrinos above 100 TeV during hadronic flares can be up to ∼3-10 times higher than the expected number in standard leptohadronic models. Still, frequent hadronic flaring activity is necessary for explaining the detected neutrino event IceCube-200107A.

Keywords: Neutrino astronomy, Active galaxies, Non-thermal radiation sources, Gamma-rays
Imaging Spectroscopy of CME-associated Solar Radio Bursts using OVRO-LWA. We present the first results of a solar radio event observed with the Owens Valley Radio Observatory Long Wavelength Array at metric wavelengths. We examine a complex event consisting of multiple radio sources/bursts associated with a fast coronal mass ejection (CME) and an M2.1 GOES soft X-ray flare from 2015 September 20. Images of 9 s cadence are used to analyze the event over a 120 minute period, and solar emission is observed out to a distance of ≈3.5 R⊙, with an instantaneous bandwidth covering 22 MHz within the frequency range of 40-70 MHz. We present our results from the investigation of the radio event, focusing particularly on one burst source that exhibits outward motion, which we classify as a moving type IV burst. We image the event at multiple frequencies and use the source centroids to obtain the velocity for the outward motion. Spatial and temporal comparison with observations of the CME in white light from the C2 coronagraph of the Large Angle and Spectrometric COronagraph, indicates an association of the outward motion with the core of the CME. By performing graduated-cylindrical-shell reconstruction of the CME, we constrain the density in the volume. The electron plasma frequency obtained from the density estimates do not allow us to completely dismiss plasma emission as the underlying mechanism. However, based on source height and smoothness of the emission in frequency and time, we argue that gyrosynchrotron is the more plausible mechanism. We use gyrosynchrotron spectral-fitting techniques to estimate the evolving physical conditions during the outward motion of this burst source.

Keywords: Radio continuum emission, Solar radio flares, Solar radio emission, Solar coronal mass ejections
Multiple Stellar Populations at Less-evolved Stages: Detection of Chemical Variations among Main-sequence Dwarfs in NGC 1978. Multiple stellar populations (MPs) with different chemical compositions are not exclusive features of old globular clusters (older than 10 Gyr). Indeed, recent studies reveal that younger clusters (∼2-6 Gyr-old) in the Magellanic Clouds also exhibit star-to-star chemical variations among evolved stars. However, whether MPs are present among less-evolved dwarfs of these intermediate-age clusters is still unclear. In this work, we search for chemical variations among GK-type dwarfs in the ∼2 Gyr old cluster NGC 1978, which is the youngest cluster with MPs. We exploit deep ultraviolet and visual observations from the Hubble Space Telescope to constrain the nitrogen (N) and oxygen (O) variations among main-sequence (MS) stars. To do this, we compare appropriate photometric diagrams that are sensitive to N and O with synthetic diagrams of simple stellar populations and MPs. We conclude that the G- and K-type MS stars in NGC 1978 host MPs. Our statistical analysis shows that the fraction of N-rich stars ranges from ∼40% to ∼80%, depending on the detailed distributions of N and O.

Keywords: M dwarf stars, G dwarf stars, Stellar populations, Large Magellanic Cloud, Hertzsprung Russell diagram, Star clusters
VZ Sex: X-Ray Confirmation of Its Intermediate Polar Nature. Intermediate polars are members of the cataclysmic variable binary stars. They are characterized by a moderately magnetized white dwarf accreting matter from a cool main-sequence companion star. In many cases, this accretion gives rise to a detectable X-ray emission. VZ Sex is an interesting X-ray source whose nature needs a robust confirmation. Here, we used archived XMM-Newton observations to assign the source to the intermediate polar class. We applied the Lomb-Scargle periodogram method to detect any relevant periodic feature in the 0.1-10 keV light curve and performed a spectral fitting of the X-ray spectrum in order to get information on the on-going accretion mechanism. By inspecting the periodogram, we detected a clear periodic feature at ≃20.3 minutes that we interpret as the spin period of the white dwarf. We additionally found the typical side bands expected as the consequence of the beat between the spin and the orbital period of ≃3.581 hr. The source is characterized by an unabsorbed flux of ≃2.98 × 10-12 erg cm-2 s-1 corresponding to an intrinsic luminosity of ≃7 × 1031 erg s-1 for a distance of ≃433 pc. The existence of such features allows us to classify VZ Sex as a clear member of the intermediate polar class. Furthermore, with the estimated WD spin, the ratio Pspin/Porb is ≃0.09, i.e., consistent with that expected for a typical IP system above the period gap. In addition, the estimated intrinsic luminosity opens the possibility that a bridge linking the normally bright IPs to the faint population of sources does exist.

Keywords: White dwarf stars, Cataclysmic variable stars, X-ray binary stars, Novae
Chandra Detection of Three X-Ray Bright Quasars at z &gt; 5. We report Chandra detection of three UV-bright radio-quiet quasars at z ≳ 5. We have collected a sufficient number of photons to extract an X-ray spectrum of each quasar to measure their basic X-ray properties, such as the X-ray flux, power-law photon index (Γ), and optical-to-X-ray spectral slope (αOX). J074749+115352 at z = 5.26 is the X-ray brightest radio-quiet quasar at z &gt; 5. It may have a short timescale variation (on a timescale of ∼3800 s in the observer's frame, or ∼600 s in the rest frame), which is, however, largely embedded in the statistical noise. We extract phase folded spectra of this quasar. There are two distinguishable states: a "high soft" state with an average X-ray flux ∼2.7 times the "low hard" state, and a significantly steeper X-ray spectral slope ( ${\rm{\Gamma }}={2.40}_{-0.32}^{+0.33}$ versus ${1.78}_{-0.24}^{+0.25}$ ). We also compare the three quasars detected in this paper to other quasar samples. We find that J074749+115352, with an SMBH mass of MSMBH ≈ 1.8 × 109 M⊙ and an Eddington ratio of λEdd ≈ 2.3, is extraordinarily X-ray bright. It has an average αOX = -1.46 ± 0.02 and a 2-10 keV bolometric correction factor of Lbol/L2-10 keV = 42.4 ± 5.8, both significantly depart from some well defined scaling relations. We compare Γ of the three quasars to other samples at different redshifts, and do not find any significant redshift evolution based on the limited sample of z &gt; 5 quasars with reliable measurements of the X-ray spectral properties.

Keywords: Early universe, Supermassive black holes, X-ray quasars, High-redshift galaxies
Deep Learning for Line Intensity Mapping Observations: Information Extraction from Noisy Maps. Line intensity mapping (LIM) is a promising observational method to probe large-scale fluctuations of line emission from distant galaxies. Data from wide-field LIM observations allow us to study the large-scale structure of the universe as well as galaxy populations and their evolution. A serious problem with LIM is contamination by foreground/background sources and various noise contributions. We develop conditional generative adversarial networks (cGANs) that extract designated signals and information from noisy maps. We train the cGANs using 30,000 mock observation maps with assuming a Gaussian noise matched to the expected noise level of NASA's SPHEREx mission. The trained cGANs successfully reconstruct Hα emission from galaxies at a target redshift from observed, noisy intensity maps. Intensity peaks with heights greater than 3.5σnoise are located with 60% precision. The one-point probability distribution and the power spectrum are accurately recovered even in the noise-dominated regime. However, the overall reconstruction performance depends on the pixel size and on the survey volume assumed for the training data. It is necessary to generate training mock data with a sufficiently large volume in order to reconstruct the intensity power spectrum at large angular scales. The suitably trained cGANs perform robustly against variations of the galaxy line emission model. Our deep-learning approach can be readily applied to observational data with line confusion and with noise.

Keywords: Observational cosmology, Astronomical methods, Large-scale structure of the universe
Insight-HXMT Observations of a Possible Fast Transition from the Jet- to Wind-dominated State during a Huge Flare of GRS 1915+105. We present the analysis of the brightest flare that was recorded in the Insight-HMXT data set in a broad energy range (2-200 keV) from the microquasar GRS 1915+105 during an unusual low-luminosity state. This flare was detected by Insight-HXMT among a series of flares during 2019 June 2 UTC 16:37:06-20:11:36 with a 2-200 keV luminosity of 3.4-7.27 × 1038 erg s-1. Basing on the broadband spectral analysis, we find that the flare spectrum shows different behaviors during bright and faint epochs. The spectrum of the flare can be fitted with a model dominated by a power-law component. Additional components show up in the bright epoch with a hard tail and in the faint epoch with an absorption line of ∼6.78 keV. The reflection component of the latter is consistent with an inner disk radius ∼five times larger than that of the former. These results on the giant flare during the "unusual" low-luminosity state of GRS 1915+105 may suggest that the source experiences a possible fast transition from a jet-dominated state to a wind-dominated state. We speculate that the evolving accretion disk and the large-scale magnetic field may play important roles in this peculiar huge flare.

Keywords: Accretion, X-ray binary stars, Black holes, Relativistic jets, Magnetic fields
Rapid Deceleration of Blast Waves Witnessed in Tycho's Supernova Remnant. In spite of their importance as standard candles in cosmology and as major major sites of nucleosynthesis in the universe, the kinds of progenitor systems that lead to Type Ia supernovae (SNe Ia) remains a subject of considerable debate in the literature. This is true even for the case of Tycho's supernova (SN) that exploded in 1572, although it has been deeply studied both observationally and theoretically. Analyzing X-ray data of Tycho's supernova remnant (SNR) obtained with Chandra in 2003, 2007, 2009, and 2015, we discover that the expansion before 2007 was substantially faster than radio measurements reported in the past decades and then rapidly decelerated during the last ∼15 yr. The result is well explained if the shock waves recently hit a wall of dense gas surrounding the SNR. In fact, such a gas structure is expected in the so-called single-degenerate scenario, in which the progenitor is a binary system consisting of a white dwarf and a stellar companion, whereas it is not generally predicted by a competing scenario, the double-degenerate scenario, which has a binary of two white dwarfs as the progenitor. Our result thus favors the former scenario. This work also demonstrates a novel technique to probe gas environments surrounding SNRs and thus disentangle the two progenitor scenarios for SNe Ia.

Keywords: Molecular clouds, Supernova remnants, Type Ia supernovae, X-ray sources, Interstellar medium, Circumstellar gas
Physics of Nonuniversal Larson's Relation. From a new perspective, we reexamine self-gravity and turbulence jointly, in hopes of understanding the physical basis for one of the most important empirical relations governing clouds in the interstellar medium (ISM), the Larson's relation relating velocity dispersion (σR) to cloud size (R). We report on two key new findings. First, the correct form of the Larson's relation is ${\sigma }_{R}={\alpha }_{v}^{1/5}{\sigma }_{\mathrm{pc}}{(R/1\mathrm{pc})}^{3/5}$ , where αv is the virial parameter of clouds and σpc is the strength of the turbulence, if the turbulence has the Kolmogorov spectrum. Second, the amplitude of Larson's relation, σpc, is not universal, differing by a factor of about 2 between clouds on the Galactic disk and those at the Galactic center, as evidenced by observational data.

Keywords: Gravitational equilibrium, Interstellar dynamics, Dense interstellar clouds, Gravitational interaction, Interstellar magnetic fields, Interstellar clouds, Gravitational collapse, Interstellar medium, Star formation, Dark interstellar clouds, Diffuse interstellar clouds
On the True Fractions of Repeating and Nonrepeating Fast Radio Burst Sources. Observationally, fast radio bursts (FRBs) can be divided into repeating and apparently nonrepeating (one-off) ones. It is unclear whether all FRBs repeat and whether there are genuine nonrepeating FRBs. We attempt to address these questions using Monte Carlo simulations. We define a parameter Tc at which the accumulated number of nonrepeating sources becomes comparable to the total number of repeating sources, which is a good proxy to denote the intrinsic repeater fraction among FRBs. Assuming that both types of sources exist and their burst energies follow power-law distributions, we investigate how the observed repeater fraction evolves with time for different parameters. If the lifetime of repeaters is sufficiently long that the evolutionary effect can be neglected within the observational time span, unless Tc → ∞ (i.e., there is no genuine nonrepeating FRB source), the observed repeater fraction should increase with time first, reach a peak, and then decline. The peak time Tp and peak fraction Fr,obs,p depend on Tc and other repeating rate parameters. With the current data, we pose a lower limit Tc &gt; 0.1 day for reasonable parameter values. We predict that future continuous monitoring of FRBs with CHIME or similar wide-field radio telescopes would obtain an Fr,obs less than 0.04. The detection of a smaller peak value Fr,obs,p &lt; 0.04 in the near future would disfavor the ansatz that "all FRB sources repeat."

Keywords: Radio transient sources
MUSE Reveals Extended Circumnuclear Outflows in the Seyfert 1 NGC 7469. NGC 7469 is a well-known luminous infrared galaxy, with a circumnuclear star formation ring (∼830 pc radius) surrounding a Seyfert 1 active galactic nucleus (AGN). Nuclear unresolved winds were previously detected in X-rays and ultraviolet, as well as an extended biconical outflow in infrared coronal lines. We search for extended outflows by measuring the kinematics of the Hβ and [O III] λ5007 optical emission lines, in data of the Very Large Telescope/Multi-unit Spectroscopic Explorer integral field spectrograph. We find evidence of two outflow kinematic regimes: one slower regime extending across most of the star formation (SF) ring—possibly driven by the massive SF—and a faster regime (with a maximum velocity of -715 km s-1), only observed in [O III], in the western region between the AGN and the massive star-forming regions of the ring, likely AGN-driven. This work shows a case where combined AGN/SF feedback can be effectively spatially resolved, opening up a promising path toward a deeper understanding of feedback processes in the central kiloparsec of AGN.

Keywords: Galactic winds, Active galactic nuclei
Electromagnetic Signatures of Relativistic Explosions in the Disks of Active Galactic Nuclei. The disks of active galactic nuclei (AGNs), traditionally studied as feeders of the supermassive black holes (SMBHs) at their centers, are also hosts to massive stars and hence their neutron star (NS) and black hole (BH) remnants. Migration traps and gas torques in these disks favor binary formation and enhance the rate of compact object mergers. In these environments both long gamma-ray bursts (GRBs) from the death of massive stars and short GRBs from NS-NS to NS-BH mergers are expected. However, their properties in the environment of AGN disks have never been studied. Here we show that GRBs in AGN disks can display unique features, owing to the unusual relative position of the shocks that characterize the burst evolution and the Thomson photosphere of the AGN disk. In dense environments, for example, a relativistic reverse shock develops early, likely powering the prompt emission instead of internal shocks. The transient's time evolution is also compressed, yielding afterglow emission that is brighter and may peak earlier than for GRBs in the interstellar medium. Additionally, in regions of the disk that are sufficiently dense and extended, the light curves are dominated by diffusion, since the fireball remains inside the disk photosphere throughout the entire evolution. These diffusion-dominated transients emerge on timescales of days in disks around SMBHs of ∼ 106M⊙ to years for SMBHs of ∼ 108M⊙. Finally, a large fraction of events, especially in AGNs with SMBHs ≲ 107M⊙, display time-variable absorption in the X-ray band.

Keywords: Gamma-ray bursts, Active galactic nuclei, Relativistic jets