Sazuna/UAT_keywords huggingface dataset:
Exploring the Link between the X-Ray Power Spectra and Energy Spectra of Active Galactic Nuclei. Active galactic nuclei (AGN) are generally considered the scaled-up counterparts of X-ray binaries (XRBs). It is known that the power spectral density (PSD) of the X-ray emission of XRBs shows significant evolution with spectral state. It is not clear whether AGN follow a similar evolutionary trend, however, though their X-ray emission and the PSD are both variable. In this work, we study a sample of nine AGN with multiple long observations with XMM-Newton, which exhibit significant X-ray spectral variation. We perform Bayesian PSD analysis to measure the PSD shape and variation. We find that a large change in the X-ray energy spectrum (mainly the change in flux state) is often accompanied by a large change in the PSD shape. The emergence of a high-frequency break in the PSD also depends on the spectral state. Among the four sources with significant high-frequency PSD breaks detected, three show the break only in the high-flux state, while the remaining one shows it only in the low-flux state. Moreover, the X-ray rms variability in different spectral states of an AGN is found to vary by as much as 1.0 dex. These results suggest that the different variability properties observed are likely caused by different physical processes dominating different spectral states. Our results also indicate that the intrinsic PSD variation can introduce a significant fraction of the dispersion as reported for the correlations between various X-ray variability properties and the black hole mass.

Keywords: Active galaxies, Active galactic nuclei, X-ray active galactic nuclei
Dependence of the Continuum Intensities on the Magnetic Fields at Different Evolution Phases of Sunspots. The relationship between the continuum intensities and magnetic fields for stable and decaying sunspots is analyzed using the scattered-light-corrected data from the Helioseismic and Magnetic Imager. From our analysis, the main differences between stable and decaying sunspots are as follows. In the continuum intensity range from 0.35I qs to 0.65I qs, where I qs is the continuum intensity of the quiet solar surface, the relationship between continuum intensity and transverse magnetic field and the relationship between continuum intensity and inclination display a much higher scatter during the decaying phase of the sunspots. During and after the formation of the light bridge, the scatter plots show a bifurcation that indicates that the two umbrae separated by the light bridge have different thermodynamic properties. The continuum intensity of the umbra in a decaying sunspot is brighter than that of the stable sunspot, indicating that the temperatures in the umbra of decaying sunspots are higher. Furthermore, our results show that the mean continuum intensity of the umbra gradually increases during the decay of the sunspot, but the mean continuum intensity of the penumbra remains constant. Simultaneously, the vertical and transverse magnetic field strengths in the umbra gradually decrease, and the vertical magnetic field strengths in the penumbra gradually increase. The changes in the umbra occur earlier than the changes in the penumbra of the decaying sunspot, suggesting that the umbral and penumbral decay may be an interdependent process during the decay of the sunspot.

Keywords: Solar photosphere, Sunspots, Solar magnetic fields
The Missing Satellite Problem outside of the Local Group. II. Statistical Properties of Satellites of Milky Way-like Galaxies. We present a new observation of satellite galaxies around seven Milky Way (MW)-like galaxies located outside of the Local Group (LG) using Subaru/Hyper Suprime-Cam imaging data to statistically address the missing satellite problem. We select satellite galaxy candidates using magnitude, surface brightness, Sérsic index, axial ratio, FWHM, and surface brightness fluctuation cuts, followed by visual screening of false positives such as optical ghosts of bright stars. We identify 51 secure dwarf satellite galaxies within the virial radius of nine host galaxies, two of which are drawn from the pilot observation presented in Paper I. We find that the average luminosity function of the satellite galaxies is consistent with that of the MW satellites, although the luminosity function of each host galaxy varies significantly. We observe an indication that more massive hosts tend to have a larger number of satellites. Physical properties of the satellites such as the size-luminosity relation are also consistent with the MW satellites. However, the spatial distribution is different; we find that the satellite galaxies outside of the LG show no sign of concentration or alignment, while that of the MW satellites is more concentrated around the host and exhibits a significant alignment. As we focus on relatively massive satellites with M  V  &lt; -10, we do not expect that the observational incompleteness can be responsible here. This trend might represent a peculiarity of the MW satellites, and further work is needed to understand its origin.

Keywords: Luminosity function, Observational cosmology, Dwarf galaxies
X-Ray Redshifts of Obscured Chandra Source Catalog Active Galactic Nuclei. We have computed obscured active galactic nuclei (AGN) redshifts using the XZ method, adopting a broad treatment in which we employed a wide-ranging data set and worked primarily at the XZ counts sensitivity threshold, culminating with a redshift catalog containing 121 sources that lack documented redshifts. We considered 363 obscured AGN from the Chandra Source Catalog Release 2.0, 59 of which were selected using multiwavelength criteria while 304 were X-ray selected. One third of the data set had crossmatched spectroscopic or photometric redshifts. These sources, dominated by low-z and low-N  H  AGN, were supplemented by 1000 simulations to form a data set for testing the XZ method. We used a multilayer perceptron neural network to examine and predict cases in which XZ fails to reproduce the known redshift, yielding a classifier that can identify and discard poor redshift estimates. This classifier demonstrated a statistically significant ~3σ improvement over the existing XZ redshift information gain filter. We applied the machine-learning model to sources with no documented redshifts, resulting in the 121 source new redshift catalog, all of which were X-ray selected. Our neural network's performance suggests that nearly 90% of these redshift estimates are consistent with hypothetical spectroscopic or photometric measurements, strengthening the notion that redshifts can be reliably estimated using only X-rays, which is valuable to current and future missions such as Athena. We have also identified a possible Compton-thick candidate that warrants further investigation.

Keywords: X-ray astronomy, X-ray active galactic nuclei, Active galactic nuclei, X-ray sources, Redshift surveys
Global Modeling of Nebulae with Particle Growth, Drift, and Evaporation Fronts. III. Redistribution of Refractories and Volatiles. Formation of the first planetesimals remains an unsolved problem. Growth by sticking must initiate the process, but multiple studies have revealed a series of barriers that can slow or stall growth, most of them due to nebula turbulence. In a companion paper, we study the influence of these barriers on models of fractal aggregate and solid, compact particle growth in a viscously evolving solar-like nebula for a range of turbulent intensities α t = 10-5-10-2. Here, we examine how the disk composition in these same models changes with time. We find that advection and diffusion of small grains and vapor, and radial inward drift for larger compact particles and fractal aggregates, naturally lead to diverse outcomes for planetesimal composition. Larger particles can undergo substantial inward radial migration due to gas drag before being collisionally fragmented or partially evaporating at various temperatures. This leads to enhancement of the associated volatile in both vapor inside, and solids outside, their respective evaporation fronts, or snowlines. In cases of lower α t, we see narrow belts of volatile or supervolatile material develop in the outer nebula, which could be connected to the bands of pebbles seen by the Atacama Large Millimeter/submillimeter Array. Volatile bands, which migrate inwards as the disk cools, can persist over long timescales as their gas phase continues to advect or diffuse outward across its evaporation front. These belts could be sites where supervolatile-rich planetesimals form, such as the rare CO-rich and water-poor comets; giant planets formed just outside the H2O snowline may be enhanced in water.

Keywords: Protoplanetary disks
Global Modeling of Nebulae with Particle Growth, Drift, and Evaporation Fronts. II. The Influence of Porosity on Solids Evolution. Incremental particle growth in turbulent protoplanetary nebulae is limited by a combination of barriers that can slow or stall growth. Moreover, particles that grow massive enough to decouple from the gas are subject to inward radial drift, which could lead to the depletion of most disk solids before planetesimals can form. Compact particle growth is probably not realistic. Rather, it is more likely that grains grow as fractal aggregates, which may overcome this so-called radial drift barrier because they remain more coupled to the gas than compact particles of equal mass. We model fractal aggregate growth and compaction in a viscously evolving solar-like nebula for a range of turbulent intensities α t = 10-5-10-2. We do find that radial drift is less influential for porous aggregates over much of their growth phase; however, outside the water snowline fractal aggregates can grow to much larger masses with larger Stokes numbers more quickly than compact particles, leading to rapid inward radial drift. As a result, disk solids outside the snowline out to ~10-20 au are depleted earlier than in compact growth models, but outside ~20 au material is retained much longer because aggregate Stokes numbers there remain lower initially. Nevertheless, we conclude even fractal models will lose most disk solids without the intervention of some leapfrog planetesimal forming mechanism such as the streaming instability (SI), though conditions for the SI are generally never satisfied, except for a brief period at the snowline for α t = 10-5.

Keywords: Protoplanetary disks
Overview of the Remote Sensing Observations from PSP Solar Encounter 10 with Perihelion at 13.3 R <SUB>⊙</SUB>. The closest perihelion pass of Parker Solar Probe (PSP), so far, occurred between 2021 November 16 and 26 and reached ~13.29 R ☉ from Sun center. This pass resulted in very unique observations of the solar corona by the Wide-field Instrument for Solar PRobe (WISPR). WISPR observed at least 10 coronal mass ejections (CMEs), some of which were so close that the structures appear distorted. All of the CMEs appeared to have a magnetic flux rope (MFR) structure, and most were oriented such that the view was along the axis orientation, revealing very complex interiors. Two CMEs had a small MFR develop in the interior, with a bright circular boundary surrounding a very dark interior. Trailing the larger CMEs were substantial outflows of small blobs and flux-rope-like structures within striated ribbons, lasting for many hours. When the heliospheric plasma sheet was inclined, as it was during the days around perihelion on 2021 November 21, the outflow was over a very wide latitude range. One CME was overtaken by a faster one, with a resultant compression of the rear of the leading CME and an unusual expansion in the trailing CME. The small Thomson surface creates brightness variations of structures as they pass through the field of view. In addition to this dynamic activity, a brightness band from excess dust along the orbit of asteroid/comet 3200 Phaethon is also seen for several days.

Keywords: Solar coronal streamers, Solar wind, Solar K corona, Solar coronal mass ejections
A Uniform Retrieval Analysis of Ultra-cool Dwarfs. IV. A Statistical Census from 50 Late-T Dwarfs. The spectra of brown dwarfs are key to exploring the chemistry and physics that take place in their atmospheres. Late-T dwarf spectra are particularly diagnostic, due to their relatively cloud-free atmospheres and deep molecular bands. With the use of powerful atmospheric retrieval tools applied to the spectra of these objects, direct constraints on molecular/atomic abundances, gravity, and vertical thermal profiles can be obtained, enabling a broad exploration of the chemical/physical mechanisms operating in their atmospheres. We present a uniform retrieval analysis on low-resolution Infrared Telescope Facility SpeX near-infrared spectra for a sample of 50 T dwarfs, including new observations as part of a recent volume-limited survey. This analysis more than quadruples the sample of T dwarfs with retrieved temperature profiles and abundances (H2O, CH4, NH3, K, and subsequent C/O and metallicities). We are generally able to constrain the effective temperatures to within 50 K, the volume mixing ratios for major species to within 0.25 dex, the atmospheric metallicities [M/H] to within 0.2, and the C/O ratios to within 0.2. We compare our retrieved constraints on the thermal structures, chemistry, and gravities of these objects with predictions from self-consistent radiative-convective equilibrium models and find, in general, though with substantial scatter, consistency with solar composition chemistry and the thermal profiles of the neighboring stellar FGK population. Objects with notable discrepancies between the two modeling techniques and potential mechanisms for their differences, be they related to the modeling approach or physically motivated, are discussed more thoroughly in the text.

Keywords: Brown dwarfs, Methane, Bayesian statistics, Atmospheric composition, Metallicity, T dwarfs
Public Release of A-SLOTH: Ancient Stars and Local Observables by Tracing Halos. The semianalytical model A-SLOTH (Ancient Stars and Local Observables by Tracing Halos) is the first public code that connects the formation of the first stars and galaxies to observables. After several successful projects with this model, we publish the source code (https://gitlab.com/thartwig/asloth) and describe the public version in this paper. The model is based on dark matter merger trees that can either be generated based on Extended Press-Schechter theory or be imported from dark matter simulations. On top of these merger trees, A-SLOTH applies analytical recipes for baryonic physics to model the formation of both metal-free and metal-poor stars and the transition between them with unprecedented precision and fidelity. A-SLOTH samples individual stars and includes radiative, chemical, and mechanical feedback. It is calibrated based on six observables, such as the optical depth to Thomson scattering, the stellar mass of the Milky Way and its satellite galaxies, the number of extremely metal-poor stars, and the cosmic star formation rate density at high redshift. A-SLOTH has versatile applications with moderate computational requirements. It can be used to constrain the properties of the first stars and high-z galaxies based on local observables, predicts properties of the oldest and most metal-poor stars in the Milky Way, can serve as a subgrid model for larger cosmological simulations, and predicts next-generation observables of the early universe, such as supernova rates or gravitational wave events.

Keywords: Open source software, Population III stars, Milky Way formation, Population II stars, High-redshift galaxies, Astronomical simulations
Insight-HXMT Observation of 4U 1608-52: Evidence of Interplay between a Thermonuclear Burst and Accretion Environment. A Type I burst could influence the accretion process through radiation pressure and Comptonization both for the accretion disk and the corona/boundary layer of an X-ray binary, and vice versa. We investigate the temporal evolution of a bright photospheric radius expansion (PRE) burst of 4U 1608-52 detected by Insight-HXMT in 1-50 keV, with the aim to study the interplay between the burst and persistent emission. Apart from the emission from the neutron star (NS) surface, we find residuals in both the soft (&lt;3 keV) and hard (&gt;10 keV) X-ray bands. Time-resolved spectroscopy reveals that the excess can be attributed to either an enhanced preburst/persistent emission or the Comptonization of the burst emission by the corona/boundary layer. The Comptonization model is a convolution thermal-Comptonization model (thcomp in XSPEC), and the Comptonization parameters are fixed at the values derived from the persistent emission. We find, during the PRE phase, after the enhanced preburst/persistent emission or the Comptonization of the burst emission is removed, the NS surface emission shows a plateau and then a rise until the photosphere touches down on the NS surface, resulting in a flux peak at that moment. We speculate that the findings above correspond to the lower part of the NS surface that is obscured by the disk being exposed to the line of sight due to the evaporation of inner disk by the burst emission. The consistency between the f  a  model and convolution thermal-Comptonization model indicates the interplay between thermonuclear bursts and accretion environments. These phenomena do not usually show up in conventional blackbody model fittings, which may be due to the low count rate and narrow energy coverage in previous observations.

Keywords: X-ray bursters
The Physical Properties of Massive Green Valley Galaxies as a Function of Environments at 0.5 &lt; z &lt; 2.5 in 3D-HST/Candels Fields. To investigate the effects of environment in the quenching phase, we study the empirical relations for green valley (GV) galaxies between overdensity and other physical properties (i.e., effective radius r e , Sérsic indices n, and specific star formation rate (sSFR)). Based on five 3D-HST/CANDELS fields, we construct a large sample of 2126 massive (M ⋆ &gt; 1010 M ☉) GV galaxies at 0.5 &lt; z &lt; 2.5 and split it into the higher overdensity quarter and the lower overdensity quarter. The results shows that GV galaxies in denser environments have higher n values and lower sSFR at 0.5 &lt; z &lt; 1, while there is no discernible distinction at 1 &lt; z &lt; 2.5. No significant enlarging or shrinking is found for GV galaxies in different environments within the same redshift bin. This suggests that a dense environment would promote the growth of bulges and suppress star formation activity of GV galaxies at 0.5 &lt; z &lt; 1.5 but would not affect the galaxy size. We also study the dependence of the fraction of three populations (blue cloud, GV, and red sequence) on both environments and M ⋆. At a given M ⋆, blue cloud fraction goes down with increasing environment density, while red sequence fraction is opposite. For the most massive GV galaxies, a sharp drop appears in the denser environment. Coupled with the mass dependence of three fractions in different redshift bins, our result implies that stellar mass and environments jointly promote the quenching process. Such a dual effect is also confirmed by recalculating the new effective GV fraction as the number of GV galaxies over the number of nonquiescent galaxies.

Keywords: Stellar properties, Galaxy environments, Green valley galaxies, Star formation, Galaxy quenching
KIC 2857323: A Double-mode High-amplitude δ Scuti Star with Amplitude Decline of the First Overtone Mode. We investigate the pulsating behavior of KIC 2857323 using high-precision observations from the Kepler mission. Fourier analysis of 4 yr time-series data reveals five independent frequencies for the light variation. Among them, two strong frequencies f 1 and f 3 with a period ratio of 0.774 identify this star as a double-mode (i.e., the fundamental mode F0 and first overtone mode F1) high-amplitude δ Scuti star (HADS). Seismic modeling using the two radial modes F0 and F1 indicates that KIC 2857323 is a main-sequence star with mass M = 1.78 ± 0.02 M ⊙ and metallicity Z from 0.009 to 0.012. We analyze the phase and amplitude variations of F0 and F1 using the phase modulation method and find that the first overtone mode F1 shows a slow decline in amplitude. We discuss several possible causes for the amplitude variation and speculate that the amplitude decline in this star may be due to pulsation energy loss. We note that KIC 2857323 is the first double-mode HADS to show amplitude decline and warrants further study to ascertain its nature.

Keywords: Asteroseismology, Delta Scuti variable stars, Stellar evolution
Solar and Stellar Flares: Frequency, Active Regions, and Stellar Dynamo. We demonstrate that for weak flares the dependence of their frequency occurrence on spottedness can be rather weak. The fact is that such flares can occur in both small and large active regions. At the same time, powerful large flares of classes M and X occur much more often in large active regions. In energy estimates, the mean magnetic field in starspots can also be assumed to be equal to the mean field in the sunspot umbra. So the effective mean magnetic field is 900 Mx cm-2 in sunspots and 2000 Mx cm-2 in starspots. Moreover, the height of the energy storage cannot be strictly proportional to A 1/2. For stars, the fitting factor is an order of magnitude smaller. The analysis of the occurrence rate of powerful solar X-ray flares of class M and X and superflares on stars shows that, with allowance for the difference in the spottedness and compactness of active regions, both sets can be described by a single model. Thus, the problem of superflares on stars and their absence on the Sun is reduced to the problem of the difference in the effectiveness of the dynamo mechanisms.

Keywords: Solar activity, Solar flares, Stellar activity
Can Cooling and Heating Functions Be Modeled with Homogeneous Radiation Fields?. Cooling and heating functions describe how radiative processes impact the thermal state of a gas as a function of its temperature and other physical properties. In a most general case the functions depend on the detailed distributions of ionic species and on the radiation spectrum. Hence, these functions may vary on a very wide range of spatial and temporal scales. In this paper, we explore cooling and heating functions between 5 ≤ z ≤ 10 in simulated galaxies from the Cosmic Reionization On Computers project. We compare three functions: (1) the actual cooling and heating rates of hydrodynamic cells as a function of cell temperature, (2) the median cooling and heating functions computed using median interstellar medium (ISM) properties (median ISM), and (3) the median of the cooling and heating functions of all gas cells (instantaneous). We find that the median ISM and instantaneous approaches to finding a median cooling and heating function give identical results within the spread due to cell-to-cell variation. However, the actual cooling (heating) rates experienced by the gas at different temperatures in the simulations do not correspond to either summarized cooling (heating) functions. In other words, the thermodynamics of the gas in the simulations cannot be described by a single set of a cooling plus a heating function with a spatially constant radiation field that could be computed with common tools, such as CLOUDY.

Keywords: Cosmology, Galaxy formation, Interstellar radiation field, Computational methods, High-redshift galaxies, Galaxies