Sazuna/UAT_keywords huggingface dataset:
A Rapid and Large-amplitude X-Ray Dimming Event in a z ≈ 2.6 Radio-quiet Quasar. We report a dramatic, fast X-ray dimming event in a z = 2.627 radio-quiet type 1 quasar, which has an estimated supermassive black hole (SMBH) mass of 6.3 × 109 M ⊙. In the high X-ray state, it showed a typical level of X-ray emission relative to its UV/optical emission. Then its 0.5-2 keV (rest-frame 1.8-7.3 keV) flux dropped by a factor of ≈7.6 within two rest-frame days. The dimming is associated with spectral hardening, as the 2-7 keV (rest-frame 7.3-25.4 keV) flux dropped by only 17%, and the effective power-law photon index of the X-ray spectrum changed from ≈2.3 to ≈0.9. The quasar has an infrared (IR)-to-UV spectral energy distribution and a rest-frame UV spectrum similar to those of typical quasars, and it does not show any significant long-term variability in the IR and UV/optical bands. Such an extremely fast and large-amplitude X-ray variability event has not been reported before in luminous quasars with such massive SMBHs. The X-ray dimming is best explained by a fast-moving absorber crossing the line of sight and fully covering the X-ray emitting corona. Adopting a conservatively small size of 5 GM BH/c 2 for the X-ray corona, the transverse velocity of the absorber is estimated to be ≈0.9c. The quasar is likely accreting with a high or even super-Eddington accretion rate, and the high-velocity X-ray absorber is probably related to a powerful accretion-disk wind. Such an energetic wind may eventually evolve into a massive galactic-scale outflow, providing efficient feedback to the host galaxy.

Keywords: X-ray quasars, Active galactic nuclei, X-ray active galactic nuclei, Quasars
A Statistical Detection of Wide Binary Systems in the Ultrafaint Dwarf Galaxy Reticulum II. Binary stars can inflate the observed velocity dispersion of stars in dark matter-dominated systems such as ultrafaint dwarf galaxies (UFDs). However, the population of binaries in UFDs is poorly constrained by observations, with preferred binary fractions for individual galaxies ranging from a few percent to near unity. Searching for wide binaries through nearest neighbor (NN) statistics (or the two-point correlation function) has been suggested in the literature, and we apply this method for the first time to detect wide binaries in a UFD. By analyzing the positions of stars in Reticulum II (Ret II) from Hubble Space Telescope images, we search for angularly resolved wide binaries in Ret II. We find that the distribution of their NN distances shows an enhancement at projected separations of ≲1″ relative to a model containing no binaries. We show that such an enhancement can be explained by a wide binary fraction of ${f}_{b}\approx {0.007}_{-0.003}^{+0.008}$ at separations of more than 3000 au. Under the assumption that the binary separation distribution is similar to that in the Milky Way, the total binary fraction in Ret II may be on the order of 50%. We also use the observed magnitude distribution of stars in Ret II to constrain the initial mass function over the mass range 0.34-0.78 M ⊙, finding that a shallow power-law slope of 1.01 ≤ α ≤ 1.15 matches the data.

Keywords: Cold dark matter, Dwarf galaxies, Binary stars
Decayless Oscillations in Solar Coronal Bright Points. Decayless kink oscillations of solar coronal loops (or decayless oscillations for short) have attracted great attention since their discovery. Coronal bright points (CBPs) are mini-active regions and consist of loops with a small size. However, decayless oscillations in CBPs have not been widely reported. In this study, we identified this kind of oscillations in some CBPs using 171 Å images taken by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. After using the motion magnification algorithm to increase oscillation amplitudes, we made time-distance maps to identify the oscillatory signals. We also estimated the loop lengths and velocity amplitudes. We analyzed 23 CBPs and found 31 oscillation events in 16 of them. The oscillation periods range from 1 to 8 minutes (on average about 5 minutes), and the displacement amplitudes have an average value of 0.07 Mm. The average loop length and velocity amplitude are 23 Mm and 1.57 km s-1, respectively. Relationships between different oscillation parameters are also examined. Additionally, we performed a simple model to illustrate how these subpixel oscillation amplitudes (less than 0.4 Mm) could be detected. Results of the model confirm the reliability of our data processing methods. Our study shows for the first time that decayless oscillations are common in small-scale loops of CBPs. These oscillations allow for seismological diagnostics of the Alfvén speed and magnetic field strength in the corona.

Keywords: Solar oscillations, Solar coronal seismology, Quiet solar corona
Massive Compact Dust Disk with a Gap around CW Tau Revealed by ALMA Multiband Observations. Compact protoplanetary disks with a radius of ≲50 au are common around young low-mass stars. We report high-resolution ALMA dust continuum observations toward a compact disk around CW Tau at Bands 4 (λ = 2.2 mm), 6 (1.3 mm), 7 (0.89 mm), and 8 (0.75 mm). The spectral energy distribution shows the spectral slope of 2.0 ± 0.24 between 0.75 and 1.3 mm, while it is 3.7 ± 0.29 between 2.17 and 3.56 mm. The steep slope between 2.17 and 3.56 mm is consistent with that of optically thin emission from small grains (≲350 μm). We perform parametric fitting of the ALMA data to characterize the dust disk. Interestingly, if the dust-to-gas mass ratio is 0.01, the Toomre Q parameter reaches ~1-3, suggesting that the CW Tau disk might be marginally gravitationally unstable. The total dust mass is estimated as ~250 M ⊕ for the maximum dust size of 140 μm that is inferred from the previous Band 7 polarimetric observation and at least 80 M ⊕ even for larger grain sizes. This result shows that the CW Tau disk is quite massive in spite of its smallness. Furthermore, we clearly identify a gap structure located at ~20 au, which might be induced by a giant planet. In spite of these interesting characteristics, the CW Tau disk has normal disk luminosity, size, and spectral index at ALMA Band 6, which could be a clue to the mass budget problem in Class II disks.

Keywords: Dust continuum emission, Protoplanetary disks, Planet formation
Seven Years of SN 2014C: A Multiwavelength Synthesis of an Extraordinary Supernova. SN 2014C was originally classified as a Type Ib supernova, but at phase ϕ = 127 days, post-explosion strong Hα emission was observed. SN 2014C has since been observed in radio, infrared, optical and X-ray bands. Here we present new optical spectroscopic and photometric data spanning ϕ = 947-2494 days post-explosion. We address the evolution of the broadened Hα emission line, as well as broad [O III] emission and other lines. We also conduct a parallel analysis of all publicly available multiwavelength data. From our spectra, we find a nearly constant Hα FWHM velocity width of ~2000 km s-1 that is significantly lower than that of other broadened atomic transitions (~3000-7000 km s-1) present in our spectra ([O I] λ6300; [O III] λ λ4959, 5007; He I λ7065; [Ca II] λ λ7291, 7324). The late radio data demand a fast forward shock (~10,000 km s-1 at ϕ = 1700 days) in rarified matter that contrasts with the modest velocity of the Hα. We propose that the infrared flux originates from a toroidal-like structure of hydrogen surrounding the progenitor system, while later emission at other wavelengths (radio, X-ray) likely originates predominantly from the reverse shock in the ejecta and the forward shock in the quasi-spherical progenitor He-wind. We propose that the Hα emission arises in the boundary layer between the ejecta and torus. We also consider the possible roles of a pulsar and a binary companion.

Keywords: Type Ib supernovae, Type II supernovae, Circumstellar matter, X-ray transient sources, Circumstellar shells, Circumstellar disks, Supernovae, Radio transient sources
Mutual Inclination of Ultra-short-period Planets with Time-varying Stellar J <SUB>2</SUB> Moments. Systems with ultra-short-period (USP) planets tend to possess larger mutual inclinations compared to those with planets located farther from their host stars. This could be explained due to precession caused by stellar oblateness at early times when the host star was rapidly spinning. However, stellar oblateness reduces over time due to the decrease in the stellar rotation rate, and this may further shape the planetary mutual inclinations. In this work, we investigate in detail how the final mutual inclination varies under the effect of a decreasing J 2. We find that different initial parameters (e.g., the magnitude of J 2 and planetary inclinations) will contribute to different final mutual inclinations, providing a constraint on the formation mechanisms of USP planets. In general, if the inner planets start in the same plane as the stellar equator (or coplanar while misaligned with the stellar spin axis), the mutual inclination decreases (or increases then decreases) over time due to the decay of the J 2 moment. This is because the inner orbit typically possesses less orbital angular momentum than the outer ones. However, if the outer planet is initially aligned with the stellar spin while the inner one is misaligned, the mutual inclination nearly stays the same. Overall, our results suggest that either USP planets formed early and acquired significant inclinations (e.g., ≳30° with its companion or ≳10° with its host star spin axis for Kepler-653 c) or they formed late (≳Gyr) when their host stars rotated slower.

Keywords: Exoplanet dynamics, Exoplanet evolution, Exoplanet formation, Planetary system formation
Postexplosion Positive Jet-feedback Activity in Inner Ejecta of Core Collapse Supernovae. We conduct three-dimensional hydrodynamical simulations of weak jets that we launch into a core collapse supernova (CCSN) ejecta half an hour after the explosion and find that the interaction of the fast jets with the CCSN ejecta creates high-pressure zones that induce a backflow that results in mass accretion onto the newly born neutron star. In cases of weak jets, with a total power of ≈1045-1046 erg, the backflow mass accretion might power them up to more energetic jets by an order of magnitude. In total, the jets of the two postexplosion jet-launching episodes have enough energy to influence the morphology of the very inner ejecta, with a mass of ≈0.1 M ⊙. Our results imply that in some, probably a minority of, CCSN remnants the very inner regions might display a bipolar structure that results from postexplosion weak jets. The regions outside this part might display the morphology of jittering jets.

Keywords: Core-collapse supernovae
An Electric-field-driven Global Coronal Magnetohydrodynamics Simulation Model Using Helioseismic and Magnetic Imager Vector-magnetic-field Synoptic Map Data. We present the simulation methodology and results of our new data-driven global coronal magnetohydrodynamics (MHD) simulation model. In this model, the solar-surface electric field is first calculated such that the curl will satisfy both the induction equation and the given temporal variations of the solar-surface magnetic field. We use the synoptic maps of the Helioseismic and Magnetic Imager three-component vector-magnetic-field data to specify the solar-surface magnetic-field vector for a period from Carrington Rotations (CRs) 2106 to 2110. A set of whole-Sun three-component electric-field maps are obtained for each CR transition interval of about 27.3 days. Using the inverted electric field as the driving variable, our new global coronal MHD model, with the angular resolution of π/64, can trace the evolution of the three-dimensional coronal magnetic field that matches the specified time-dependent solar-surface magnetic-field maps and simultaneously satisfies the divergence-free condition. A set of additional boundary treatments are introduced to control the contribution of the horizontal components of the magnetic field at the weak-field regions. The strength of the solar-surface magnetic field is limited to 20 Gauss for the sake of computational stability in this study. With these numerical treatments, the nonpotential coronal features, such as twisted loop structures, and their eruptive outward motions are obtained. This present model, capable of introducing three-component solar-surface magnetic-field observation data to coronal MHD simulations, is our first step toward a better model framework for the solar corona and hence solar wind.

Keywords: Solar magnetic fields, Solar corona, Magnetohydrodynamical simulations
Diagnostics of Non-Maxwellian Electron Distributions in Solar Active Regions from Fe XII Lines Observed by the Hinode Extreme Ultraviolet Imaging Spectrometer and Interface Region Imaging Spectrograph. We present joint Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) and Interface Region Imaging Spectrograph (IRIS) observations of Fe XII lines in active regions, both on-disk and off-limb. We use an improved calibration for the EIS data, and find that the 192.4 Å/1349 Å observed ratio is consistent with the values predicted by CHIANTI and the coronal approximation in quiescent areas, but not in all active-region observations, where the ratio is often lower than expected by up to a factor of about two. We investigate a number of physical mechanisms that could affect this ratio, such as opacity and absorption from cooler material. We find significant opacity in the EIS Fe XII 193 and 195 Å lines, but not in the 192.4 Å line, in agreement with previous findings. As we cannot rule out possible EUV absorption by H, He, and He II in the on-disk observations, we focus on an off-limb observation where such absorption is minimal. After considering these, as well as possible nonequilibrium effects, we suggest that the most likely explanation for the observed low Fe XII 192.4 Å/1349 Å ratio is the presence of non-Maxwellian electron distributions in the active regions. This is in agreement with previous findings based on EIS and IRIS observations independently.

Keywords: Atomic spectroscopy, Active solar corona
Can Carbon Fractionation Provide Evidence for Aerial Biospheres in the Atmospheres of Temperate Sub-Neptunes?. The search for signs of life on other worlds has largely focused on terrestrial planets. Recent work, however, argues that life could exist in the atmospheres of temperate sub-Neptunes. Here we evaluate the usefulness of carbon dioxide isotopologues as evidence of aerial life. Carbon isotopes are of particular interest, as metabolic processes preferentially use the lighter 12C over 13C. In principle, the upcoming James Webb Space Telescope (JWST) will be able to spectrally resolve the 12C and 13C isotopologues of CO2, but not CO and CH4. We simulated observations of CO2 isotopologues in the H2-dominated atmospheres of our nearest (&lt;40 pc), temperate (equilibrium temperature of 250-350 K) sub-Neptunes with M-dwarf host stars. We find 13CO2 and 12CO2 distinguishable if the atmosphere is H2 dominated with a few percentage points of CO2 for the most idealized target with an Earth-like composition of the two most abundant isotopologues, 12CO2 and 13CO2. With a Neptune-like metallicity of 100× solar and a C/O of 0.55, we are unable to distinguish between 13CO2 and 12CO2 in the atmospheres of temperate sub-Neptunes. If atmospheric composition largely follows metallicity scaling, the concentration of CO2 in a H2-dominated atmosphere will be too low to distinguish CO2 isotopologues with JWST. In contrast, at higher metallicities, there will be more CO2, but the smaller atmospheric scale height makes the measurement impossible. Carbon dioxide isotopologues are unlikely to be useful biosignature gases for the JWST era. Instead, isotopologue measurements should be used to evaluate formation mechanisms of planets and exosystems.

Keywords: Mini Neptunes, Biosignatures, Astrobiology, Exoplanet atmospheres
Magnetic Discontinuities in the Solar Wind and Magnetosheath: Magnetospheric Multiscale Mission (MMS) Observations. We perform a statistical investigation of the geometric features of interplanetary discontinuities (IDs) in the near-Earth solar wind and magnetosheath, by utilizing 14 months of Magnetospheric Multiscale mission data. 117,669 IDs are collected, including 108,049 events in the solar wind and 6399 events in the magnetosheath, with the remnant in the magnetosphere or near the bow shock/magnetopause. We find the following: (1) the ID occurrence rate is 17.0 events hr-1 in the solar wind and 5.5 events hr-1 in the magnetosheath, (2) the field rotation angles during ID crossings in the magnetosheath exhibit a two-exponential distribution with a breakpoint at 50°, which is not observed for IDs in the solar wind, (3) the magnetosheath IDs with small field rotation angles tend to be clustered, (4) by classifying the IDs into rotational discontinuities (RDs), tangential discontinuities (TDs), either TDs or RDs (EDs), and neither TDs nor RDs (NDs), we estimate RD:TD:ED:ND = 68%:5%:20%:7% in the solar wind, and RD:TD:ED:ND = 15%:44%:18%:23% in the magnetosheath, (5) the occurrence rates of RDs and TDs are, respectively 7.95 and 0.58 events hr-1 in the solar wind, and 0.57 and 1.60 events hr-1 in the magnetosheath, (6) RDs are more likely to propagate antisunward in the plasma rest frame, especially in the magnetosheath, and (7) the average thicknesses of the RDs and TDs are estimated, respectively, as 10.4 and 8.1 proton gyroradii (r  p ) in the solar wind, and 17.4 and 5.0 r  p  in the magnetosheath. This work can improve our understanding of IDs' interaction with the terrestrial bow shock.

Keywords: Interplanetary discontinuities, Magnetohydrodynamics, Solar wind, Interplanetary magnetic fields
Young Black Hole and Neutron Star Systems in the Nearby Star-forming Galaxy M33: The NuSTAR View. We can learn about the formation and evolution of compact objects, such as neutron stars and black holes (BHs), by studying the X-ray emission from accreting systems in nearby star-forming galaxies. The hard (E &gt; 10 keV) X-ray emission in particular allows strong discrimination among the accretion states and compact object types. We conducted a NuSTAR survey (~600 ks) of the Local Group spiral galaxy M33 to study the distribution of X-ray binary (XRB) accretors in an actively star-forming environment. We constructed color-intensity and color-color diagrams to infer XRB accretion states. Using these diagrams, we have classified 28 X-ray sources in M33 by comparing their hard X-ray colors to those of known systems. Four sources lie in the parameter space occupied by X-ray pulsars, while 8, 10, and 4 sources lie in the parameter space occupied by BHs in the hard, intermediate, and soft states, respectively. The known ultraluminous X-ray source M33 X-8 is also found to be consistent with that source type. Some sources overlap within the Z/Atoll sources due to the overlap of the two categories of BHs and Z/Atoll sources. In contrast to a similar NuSTAR survey of M31 (with a low-mass XRB-dominant population), the source population in M33 is dominated by high-mass XRBs (HMXBs), allowing the study of a very different population with similar sensitivity due to the galaxy's similar distance. This characterization of a population of HMXB accretion states will provide valuable constraints for theoretical XRB population synthesis studies to their formation and evolution.

Keywords: Neutron stars, Accretion, X-ray binary stars, Black holes, Classification, High mass x-ray binary stars, Stellar classification, Triangulum Galaxy, Ultraluminous x-ray sources, Compact objects, Stellar accretion
Synthetic Population of Binary Cepheids. I. The Effect of Metallicity and Initial Parameter Distribution on Characteristics of Cepheids' Companions. The majority of classical Cepheids are binary stars, yet the contribution of companions' light to the total brightness of the system has been assumed negligible and lacked a thorough, quantitative evaluation. We present an extensive study of synthetic populations of binary Cepheids, which aims to characterize Cepheids' companions (e.g., masses, evolutionary, and spectral types), quantify their contribution to the brightness and color of Cepheid binaries, and assess the relevance of input parameters on the results. We introduce a collection of synthetic populations, which vary in metal content, initial parameter distribution, location of the instability strip edges, and star formation history. Our synthetic populations are free from the selection bias, while the percentage of Cepheid binaries is controlled by the binarity parameter. We successfully reproduce recent theoretical and empirical results: the percentage of binary Cepheids with main-sequence (MS) companions, the contrast-mass ratio relation for binary Cepheids with MS companions, the appearance of binary Cepheids with giant, evolved companions as outlier data points above the period-luminosity relation. Moreover, we present the first estimation of the percentage of binary Cepheids in the Large Magellanic Cloud and announce the quantification of the effect of binarity on the slope and zero-point of multiband period-luminosity relations, which will be reported in the next paper of this series.

Keywords: Small Magellanic Cloud, Large Magellanic Cloud, Cepheid variable stars, Astrometric binary stars, Milky Way Galaxy, Astronomical simulations
Starduster: A Multiwavelength SED Model Based on Radiative Transfer Simulations and Deep Learning. We present STARDUSTER, a supervised deep-learning model that predicts the multiwavelength spectral energy distribution (SED) from galaxy geometry parameters and star formation history by emulating dust radiative transfer simulations. The model is composed of three specifically designed neural networks, which take into account the features of dust attenuation and emission. We utilize the SKIRT radiative transfer simulation to produce data for the training data of neural networks. Each neural network can be trained using ~4000-5000 samples. Compared with the direct results of the SKIRT simulation, our deep-learning model produces ~0.005 mag and ~0.1-0.2 mag errors for dust attenuation and emission, respectively. As an application, we fit our model to the observed SEDs of IC 4225 and NGC 5166. Our model can reproduce the observations and provide reasonable measurements of the inclination angle and stellar mass. However, some predicted geometry parameters are different from an image-fitting study. Our analysis implies that including a constraint at (rest-frame) ~40 μm could alleviate the degeneracy in the parameter space for both IC 4225 and NGC 5166, leading to broadly consistent results with the image-fitting predictions. Our SED code is publicly available and can be applied to both SED fitting and SED modeling of galaxies from semianalytic models.

Keywords: Neural networks, Interstellar dust extinction, Dust continuum emission, Spectral energy distribution, Radiative transfer simulations