Sazuna/UAT_keywords huggingface dataset:
Effect of Multiple Scattering on the Transmission Spectra and the Polarization Phase Curves for Earth-like Exoplanets. It is the most appropriate time to characterize the Earth-like exoplanets in order to detect biosignature beyond the Earth because such exoplanets will be the prime targets of big-budget missions like JWST, Roman Space Telescope, HabEx, LUVOIR, Thirty Meter Telescope, Extremely Large Telescope, etc. We provide models for the transmission spectra of Earth-like exoplanets by incorporating the effects of multiple scattering. For this purpose we numerically solve the full multiple-scattering radiative transfer equations instead of using Beer-Bouguer-Lambert's law, which does not include the diffuse radiation due to scattering. Our models demonstrate that the effect of this diffuse transmission radiation can be observationally significant, especially in the presence of clouds. We also calculate the reflection spectra and polarization phase curves of Earth-like exoplanets by considering both cloud-free and cloudy atmospheres. We solve the 3D vector radiative transfer equations numerically and calculate the phase curves of albedo and disk-integrated polarization by using appropriate scattering phase matrices and integrating the local Stokes vectors over the illuminated part of the disks along the line of sight. We present the effects of the globally averaged surface albedo on the reflection spectra and phase curves as the surface features of such planets are known to significantly dictate the nature of these observational quantities. Synergic observations of the spectra and phase curves will certainly prove to be useful in extracting more information and reducing the degeneracy among the estimated parameters of terrestrial exoplanets. Thus, our models will play a pivotal role in driving future observations.

Keywords: Exoplanet atmospheric composition , Transmission spectroscopy, Starlight polarization, Radiative transfer, Atmospheric effects, Albedo, Exoplanet atmospheres
Probing the Jet-Torus Interaction in the Radio Galaxy NGC 1052 by Sulfur-bearing Molecules. The radio galaxy NGC 1052 casts absorption features of sulfur-bearing molecules, H2S, SO, SO2, and CS toward the radio continuum emission from the core and jets. Using the Atacama Large Millimeter/submillimeter Array, we have measured the equivalent widths of SO absorption features in multiple transitions and determined the temperatures of 344 ± 43 K and 26 ± 4 K in submillimeter and millimeter wavelengths, respectively. Since submillimeter and millimeter continuum represents the core and jets, the high and low temperatures of the absorbers imply a warm environment in the molecular torus and cooler downstream flows. The high temperature in the torus is consistent with the presence of 22 GHz H2O maser emission, vibrationally excited HCN and HCO+ absorption lines, and sulfur-bearing molecules in the gas phase released from dust. The origin of the sulfur-bearing gas is ascribed to the evaporation of the icy dust component through a jet-torus interaction. Shock heating is the sole plausible mechanism to maintain such a high temperature of gas and dust in the torus. The implication of the jet-torus interaction also supports the collimation of the sub-relativistic jets by the gas pressure of the torus.

Keywords: Molecular spectroscopy, Active galactic nuclei, Radio galaxies, Radio jets
Curvature of the Spectral Energy Distribution, Compton Dominance, and Synchrotron Peak Frequency in Jetted Active Galactic Nuclei. We collect a large sample with a reliable redshift detected by the Fermi satellite after 10 yr of data (4FGL-DR2), including blazars, gamma-ray narrow-line Seyfert 1 galaxies (γNLS1s), and radio galaxies. The spectral energy distributions of these Fermi sources are fitted by using a second-degree polynomial, and some important parameters including spectral curvature, synchrotron peak frequency, and peak luminosity are obtained. Based on those parameters, we discuss the Fermi blazar sequence and the particle acceleration mechanism. Our main results are as follows: (i) By studying the relationship between the synchrotron peak frequency and the synchrotron peak frequency luminosity, jet kinetic power, and gamma-ray luminosity for jetted active galactic nuclei (AGNs), we find an "L" shape in the Fermi blazar sequence. (ii) There is a significant anticorrelation between the Compton dominance, the black hole spin, and the synchrotron peak frequency for jetted AGNs, respectively. These results support that the γNLS1s and radio galaxies belong to the Fermi blazar sequence. (iii) On the basis of previous work, statistical or stochastic acceleration mechanisms can be used to explain the relationship between the synchrotron peak frequency and synchrotron curvature. For different subclasses, the correlation slopes are different, which implies that the Fermi sources of different subclasses have different acceleration mechanisms. (iv) Flat-spectrum radio quasars and γNLS1s have a higher median spin of a black hole than BL Lac objects and radio galaxies.

Keywords: BL Lacertae objects, Blazars, Radio loud quasars, Seyfert galaxies, Active galactic nuclei, Gamma-rays
Center-to-limb Variation of Transition-region Doppler Shifts in Active Regions. Studying Doppler shifts provides deep insights into the flow of mass and energy in the solar atmosphere. We perform a comprehensive measurement of Doppler shifts in the transition region and its center-to-limb variation (CLV) in the strong-field regions (∣ B ∣ ≥ 50 G) of 50 active regions (ARs), using the Si IV 1394 Å line recorded by the Interface Region Imaging Spectrometer. To locate the ARs and identify strong-field regions, we have used the magnetograms obtained by the Helioseismic and Magnetic Imager (HMI). We find that in strong-field regions, on average, all the ARs show a mean redshift ranging between 4 and 11 km s-1, which varies with ARs. These flows show a mild CLV, with sizable magnitudes at the limb and substantial scatter in the mid-longitude range. Our observations do not support the idea that redshifts in the lower transition region (T ≲ 0.1 MK) are produced by field-aligned downflows as a result of impulsive heating and they warrant an alternative interpretation, such as a downflow of type-II spicules in the presence of a chromospheric wall created by cooler type-I spicules.

Keywords: Solar atmosphere, Solar photosphere, The Sun, Sunspots, Solar spicules, Solar active regions, Solar physics, Solar magnetic fields, Solar activity, Solar chromosphere
In Situ Star Formation in Accretion Disks and Explanation of Correlation between the Black Hole Mass and Metallicity in Active Galactic Nuclei. Recent observations show that the metallicity Z BLR of the broad-line region (BLR) in active galactic nuclei (AGNs) is solar to supersolar, which is positively correlated with the mass of supermassive black holes (M BH) and does not evolve with the redshift up to z ~ 7. We revisit the M BH-Z BLR correlation with more AGNs with M BH ~ 106-8  M ⊙ and find that the positive correlation becomes flat in the low-mass range. It is known that the outer part of accretion disks is gravitationally unstable and can fragment into stars. Considering the star formation and supernovae in the outer AGN disk, we calculate the metal enrichment and find that the positive M BH-Z BLR correlation can be roughly reproduced if the stellar mass distribution is "top heavy." We find that the observed BLR size is more or less similar to the self-gravity radius of the AGN disk, which suggests that the BLR may be closely correlated with the underlying accretion process.

Keywords: Star formation, Metallicity, High-luminosity active galactic nuclei, Galaxy accretion
Two Candidates for Dual AGN in Dwarf-dwarf Galaxy Mergers. Dual active galactic nuclei (DAGN) are important for understanding galaxy-merger-triggered fueling of black holes and the hierarchical growth of structures. The least explored type of DAGN are those associated with mergers of two dwarf galaxies. According to observations and cosmological simulations, dwarf galaxies are the most abundant type of galaxies in the early universe and the galaxy-merger rate is dominated by dwarfs. However, these mergers are generally too distant to be directly observed, and low-redshift dwarf-dwarf merger-related DAGN are notoriously hard to find. In this paper, we present the first results of our large-scale search for this elusive type of object and the first two candidates for DAGN in dwarf-dwarf mergers. Both objects exhibit tidal features (tails and bridges) characteristic of galaxy mergers/interactions. One object is apparently in a late-stage merger with an AGN separation of &lt;5 kpc, while the second is in an early-stage merger with interacting galaxies having established a tidal bridge. Both objects have dual, luminous X-ray sources that are most likely due to actively accreting massive black holes. Also, both objects have infrared counterparts, with colors consistent with being AGN. Follow-up observations will provide us a glimpse into key processes that govern the earliest phases of growth of galaxies, their central black holes, and merger-induced star formation.

Keywords: Dwarf galaxies, Active galactic nuclei, Black holes, Galaxy interactions
Formation of an Intermediate Filament Driven by Small-scale Magnetic Reconnection. We present the formation process of a filament in NOAA active region 12765 from 2020 June 5 to 8, using observations from the New Vacuum Solar Telescope, the Solar Dynamics Observatory, and the Global Oscillation Network Group. We found that intermittent small-scale magnetic reconnection occurs at the northern part of the filament, and the small-scale magnetic reconnection shows the characteristics of the oscillatory reconnections. During the magnetic reconnection process, a large amount of material is continuously injected into the filament channel. Furthermore, there are bidirectional inflow and outflow, current sheets, and bright cusp-shaped structures. The velocities of the material injections range from 17 to 183 km s-1 with an average velocity of about 57 km s-1. A total of 53 material injections were found from 03:10 UT on 2020 June 5 to 00:10 UT on June 8. The total mass carried by the injection events is about 7.39 × 1014 g, and the total kinetic energy released through magnetic reconnection is approximately 3.09 × 1021 J. The projection area of the filament increased from less than 1 × 102 Mm2 to around 7 × 102 Mm2. We conclude that the filament is formed by direct material injection into the filament channel due to the small-scale magnetic reconnections.

Keywords: Solar activity, Solar magnetic fields, Solar filaments, Solar magnetic reconnection
The ESO-VLT MIKiS Survey Reloaded: Exploring the Internal Kinematics of NGC 6440. In the context of the ESO-VLT Multi-Instrument Kinematic Survey of Galactic globular clusters, here we present the line-of-sight velocity dispersion profile of NGC 6440, a massive globular cluster located in the Galactic bulge. By combining the data acquired with four different spectrographs, we obtained the radial velocity of a sample of ~1800 individual stars distributed over the entire cluster extension, from ~0.″1 to 778″ from the center. Using a properly selected sample of member stars with the most reliable radial velocity measures, we derived the velocity dispersion profile up to 250″ from the center. The profile is well described by the same King model that best fits the projected star density distribution, with a constant inner plateau (at σ 0 ~ 12 km s-1) and no evidence of a central cusp or other significant deviations. Our data allowed us to study the presence of rotation only in the innermost regions of the cluster (r &lt; 5″), revealing a well-defined pattern of ordered rotation with a position angle of the rotation axis of ~132° ± 2° and an amplitude of ~3 km s-1 (corresponding to V rot/σ 0 ~ 0.3). In addition, a flattening of the system qualitatively consistent with the rotation signal has been detected in the central region. * Based on observations collected at the European Southern Observatory, Cerro Paranal (Chile), under proposal 193.D-0232 (PI: Ferraro), 195.D-0750 (PI: Ferraro), 60.A-9489 (PI: Ferraro), and 093.D-0319 (PI: Lanzoni).

Keywords: Globular star clusters, Stellar kinematics, Spectroscopy
Delayed Development of Cool Plasmas in X-Ray Flares from the Young Sun-like Star κ <SUP>1</SUP> Ceti. The Neutron star Interior Composition Explorer (NICER) X-ray observatory observed two powerful X-ray flares equivalent to superflares from the nearby young solar-like star κ 1 Ceti in 2019. NICER follows each flare from the onset through the early decay, collecting over 30 counts s-1 near the peak, enabling a detailed spectral variation study of the flare rise. The flare in September varies quickly in ~800 s, while the flare in December has a few times longer timescale. In both flares, the hard-band (2-4 keV) light curves show typical stellar X-ray flare variations with a rapid rise and slow decay, while the soft X-ray light curves, especially of the September flare, have prolonged flat peaks. The time-resolved spectra require two temperature plasma components at kT ~0.3-1 and ~2-4 keV. Both components vary similarly, but the cool component lags by ~200 s with a four to six times smaller emission measure (EM) compared to the hot component. A comparison with hydrodynamic flare loop simulations indicates that the cool component originates from X-ray plasma near the magnetic loop footpoints that mainly cools via thermal conduction. The time lag represents the travel time of the evaporated gas through the entire flare loop. The cool component has a several times smaller EM than its simulated counterpart, suggesting a suppression of conductive cooling, possibly by the expansion of the loop cross-sectional area or turbulent fluctuations. The cool component's time lag and EM ratio provide important constraints on the flare loop geometry.

Keywords: Main sequence stars, Solar analogs, Stellar flares, Stellar x-ray flares
Evidence for AGN-regulated Cooling in Clusters at z 1.4: A Multiwavelength View of SPT-CL J0607-4448. We present a multiwavelength analysis of the galaxy cluster SPT-CL J0607-4448 (SPT0607), which is one of the most distant clusters discovered by the South Pole Telescope at z = 1.4010 ± 0.0028. The high-redshift cluster shows clear signs of being relaxed with well-regulated feedback from the active galactic nucleus (AGN) in the brightest cluster galaxy (BCG). Using Chandra X-ray data, we construct thermodynamic profiles and determine the properties of the intracluster medium. The cool-core nature of the cluster is supported by a centrally peaked density profile and low central entropy ( ${K}_{0}={18}_{-9}^{+11}$ keV cm2), which we estimate assuming an isothermal temperature profile due to the limited spectral information given the distance to the cluster. Using the density profile and gas cooling time inferred from the X-ray data, we find a mass-cooling rate ${\dot{M}}_{\mathrm{cool}}={100}_{-60}^{+90}\,{M}_{\odot }$ yr-1. From optical spectroscopy and photometry around the [O II] emission line, we estimate that the BCG star formation rate is ${\mathrm{SFR}}_{[{\rm{O}}\,{\rm\small{II}}]}={1.7}_{-0.6}^{+1.0}\,{M}_{\odot }$ yr-1, roughly two orders of magnitude lower than the predicted mass-cooling rate. In addition, using ATCA radio data at 2.1 GHz, we measure a radio jet power ${P}_{\mathrm{cav}}={3.2}_{-1.3}^{+2.1}\times {10}^{44}$ erg s-1, which is consistent with the X-ray cooling luminosity ( ${L}_{\mathrm{cool}}={1.9}_{-0.5}^{+0.2}\times {10}^{44}$ erg s-1 within r cool = 43 kpc). These findings suggest that SPT0607 is a relaxed, cool-core cluster with AGN-regulated cooling at an epoch shortly after cluster formation, implying that the balance between cooling and feedback can be reached quickly. We discuss the implications for these findings on the evolution of AGN feedback in galaxy clusters.

Keywords: Galaxy clusters, High-redshift galaxy clusters, Radio galaxies, Brightest cluster galaxies, Intracluster medium
NICER/NuSTAR Characterization of 4U 1957+11: A Near Maximally Spinning Black Hole Potentially in the Mass Gap. 4U 1957+11 is a black hole candidate system that has been in a soft X-ray spectral state since its discovery. We present analyses of recent joint NICER and NuSTAR spectra, which are extremely well described by a highly inclined disk accreting into a near maximally spinning black hole. Owing to the broad X-ray coverage of NuSTAR, the fitted spin and inclination are strongly constrained for our hypothesized disk models. The faintest spectra are observed out to 20 keV, even though their hard tail components are almost absent when described with a simple corona. The hard tail increases with luminosity, but shows clear two-track behavior with one track having appreciably stronger tails. The disk spectrum color-correction factor is anticorrelated with the strength of the hard tail (e.g., as measured by the Compton y parameter). Although the spin and inclination parameters are strongly constrained for our chosen model, the mass and distance are degenerate parameters. We use our spectral fits, along with a theoretical prior on color-correction, an observational prior on likely fractional Eddington luminosity, and an observational prior on distance obtained from Gaia studies, to present mass and distance contours for this system. The most likely parameters, given our presumed disk model, suggest a 4.6 M ⊙ black hole at 7.8 kpc observed at luminosities ranging from ≈1.7% to 9% of Eddington. This would place 4U 1957+11 as one of the few actively accreting sources within the mass gap of ≈2-5 M ⊙ where there are few known massive neutron stars or low-mass black holes. Higher mass and distance, however, remain viable.

Keywords: Accretion, X-ray astronomy, Kerr black holes, Distance measure, Stellar mass black holes, X-ray sources, Low-mass x-ray binary stars, Gamma-ray astronomy, Relativistic disks
Single- and Double-electron Capture Cross Sections for O<SUP>6+</SUP> Ion in Collisions with H<SUB>2</SUB> Molecules. Single- and double-electron capture (SEC and DEC) processes occurring in O6+ and H2 collisions are investigated in a wide-energy domain ranging from 0.1 to 100 keV u-1. Total and partial cross sections are calculated using a three-center, two-active-electron, semiclassical nonperturbative approach. To date, our close-coupling description of the collision is the most elaborate one in terms of accounting for electron correlation, molecular structures, and active channels. Our results are, in general, in good agreement with the available experimental ones for both total and partial cross sections. The comparison between the present calculations and available experimental data suggests that about 70% of the autoionization double capture may contribute to the measured SEC cross sections through postcollisional autoionization, while the stabilization of 30% of doubly excited states via the autotransfer to Rydberg states mechanism contributes to the measured DEC ones. Furthermore, we extend the understanding of the electron-capture processes on this system to impact energies above 20 keV u-1 for which no data exists. Our work provides new data for these electronic processes, which will be helpful for modeling astrophysical X-ray emissions induced by charge exchange.

Keywords: Collisional processes, Charge transfer, Atomic physics, Atomic data, Charge exchange recombination
A Multiwavelength Study of Active Galactic Nuclei in Post-merger Remnants. We investigate the role of galaxy mergers in triggering active galactic nuclei (AGN) in the nearby universe. Our analysis is based on a sample of 79 post-merger remnant galaxies with deep X-ray observations from Chandra/XMM-Newton capable of detecting a low-luminosity AGN of ≥1040.5 erg s-1. This sample is derived from a visually classified, volume-limited sample of 807 post-mergers identified in the Sloan Digital Sky Survey Data Release 14 with log M */M ☉ ≥ 10.5 and 0.02 ≤ z ≤ 0.06. We find that the X-ray AGN fraction in this sample is 55.7% ± 5.6% compared to 23.6% ± 2.8% for a mass- and redshift-matched noninteracting control sample. The multiwavelength AGN fraction (identified as an AGN in one of X-ray, IR, radio or optical diagnostics) for post-mergers is 76.6% ± 4.8% compared to 39.1% ± 3.2% for controls. Thus post-mergers exhibit a high overall AGN fraction with an excess between 2 and 4 depending on the AGN diagnostics used. In addition, we find most optical, IR, and radio AGN are also identified as X-ray AGN while a large fraction of X-ray AGN are not identified in any other diagnostic. This highlights the importance of deep X-ray imaging to identify AGN. We find that the X-ray AGN fraction of post-mergers is independent of the stellar mass above log M */M ☉ ≥ 10.5 unlike the trend seen in control galaxies. Overall, our results show that post-merger galaxies are a good tracer of the merger-AGN connection and strongly support the theoretical expectations that mergers trigger AGN.

Keywords: Galaxy mergers, Galaxy interactions, Active galactic nuclei, Galaxy evolution
A Swing of the Pendulum: The Chemodynamics of the Local Stellar Halo Indicate Contributions from Several Radial Merger Events. We find that the chemical abundances and dynamics of APOGEE and GALAH stars in the local stellar halo are inconsistent with a scenario in which the inner halo is primarily composed of debris from a single massive, ancient merger event, as has been proposed to explain the Gaia-Enceladus/Gaia Sausage (GSE) structure. The data contain trends of chemical composition with energy that are opposite to expectations for a single massive, ancient merger event, and multiple chemical evolution paths with distinct dynamics are present. We use a Bayesian Gaussian mixture model regression algorithm to characterize the local stellar halo, and find that the data are fit best by a model with four components. We interpret these components as the Virgo Radial Merger (VRM), Cronus, Nereus, and Thamnos; however, Nereus and Thamnos likely represent more than one accretion event because the chemical abundance distributions of their member stars contain many peaks. Although the Cronus and Thamnos components have different dynamics, their chemical abundances suggest they may be related. We show that the distinct low- and high-α halo populations from Nissen &amp; Schuster are explained by VRM and Cronus stars, as well as some in situ stars. Because the local stellar halo contains multiple substructures, different popular methods of selecting GSE stars will actually select different mixtures of these substructures, which may change the apparent chemodynamic properties of the selected stars. We also find that the Splash stars in the Solar region are shifted to higher v  ϕ  and slightly lower [Fe/H] than previously reported.

Keywords: Stellar astronomy, Galactic archaeology, Milky Way stellar halo, Gaussian mixture model
Analysis Methods to Localize and Characterize X-Ray Sources with the Microchannel X-Ray Telescope on Board the SVOM Satellite. The Space-based multiband astronomical Variableonboard computing resources. This Object Monitor (SVOM) is a Sino-French space mission targeting high-energy transient astrophysical objects such as gamma-ray bursts. The soft X-ray part of the spectrum is covered by the Microchannel X-ray Telescope (MXT), which is a narrow field telescope designed to localize X-ray sources precisely. This paper presents the methods implemented on board to characterize and localize X-ray sources with the MXT. A specific localization method was developed to accommodate the optical system of the MXT, which is based on "Lobster Eye" grazing incidence micropore optics. For the first time, the algorithm takes advantage of cross-correlation techniques to achieve a localization accuracy down to 2' with fewer than 200 photons, which guarantees rapid follow-up for most of the gamma-ray bursts that SVOM will observe. In this paper, we also study the limitations of the algorithm and characterize its performance.

Keywords: Space telescopes, Gamma-ray bursts