Sazuna/UAT_keywords huggingface dataset:
Long-term Optical and γ-Ray Variability of the Blazar PKS 1222+216. The γ-ray emission from flat-spectrum radio quasars (FSRQs) is thought to be dominated by the inverse Compton scattering of the external sources of photon fields, e.g., accretion disk, broad-line region (BLR), and torus. FSRQs show strong optical emission lines and hence can be a useful probe of the variability in BLR output, which is the reprocessed disk emission. We study the connection between the optical continuum, Hγ line, and γ-ray emissions from the FSRQ PKS 1222+216, using long-term (~2011-2018) optical spectroscopic data from Steward Observatory and γ-ray observations from Fermi Large Area Telescope (LAT). We measured the continuum (F C,opt) and Hγ (F Hγ ) fluxes by performing a systematic analysis of the 6029-6452 Å optical spectra. We observed stronger variability in F C,opt than F Hγ , an inverse correlation between the Hγ equivalent width and F C,opt, and a redder-when-brighter trend. Using discrete cross-correlation analysis, we found a positive correlation (DCF ~ 0.5) between the F  γ‑ray&gt;100 MeV and F C,opt (6024-6092 Å) light curves with a time lag consistent with zero at the 2σ level. We found no correlation between the F  γ‑ray&gt;100 MeV and F Hγ  light curves, probably dismissing the disk contribution to the optical and γ-ray variability. The observed strong variability in the Fermi-LAT flux and F  γ‑ray&gt;100 MeV - F C,opt correlation could be due to the changes in the particle acceleration at various epochs. We derived the optical-to-γ-ray spectral energy distributions during the γ-ray flaring and quiescent epochs that show a dominant disk component with no variability. Our study suggests that the γ-ray emission zone is likely located at the edge of the BLR or in the radiation field of the torus.

Keywords: Jets, High energy astrophysics, Blazars, Flat-spectrum radio quasars, Active galactic nuclei
Testing Rotating Regular Metrics with EHT Results of Sgr A*. The Event Horizon Telescope (EHT) observation unveiled the first image of supermassive black hole Sgr A* showing a shadow of diameter θ sh = 48.7 ± 7 μas with fractional deviation from the Schwarzschild black hole shadow diameter $\delta =-{0.08}_{-0.09}^{+0.09}\,(\mathrm{VLTI}),-{0.04}_{-0.10}^{+0.09}\,(\mathrm{Keck})$ . The Sgr A* shadow size is within 10% of the Kerr predictions, providing us with another tool to investigate the nature of strong-field gravity. We use the Sgr A* shadow observables to constrain metrics of four independent and well-motivated, parametrically different from Kerr spacetime, rotating regular spacetimes and the corresponding no-horizon spacetimes. We present constraints on the deviation parameter g of rotating regular black holes. The shadow angular diameter θ sh within the 1σ region places bounds on the parameters a and g. Together with EHT bounds on the θ sh and δ of Sgr A*, our analysis concludes that the three rotating regular black holes, i.e., Bardeen, Hayward, and Simpson-Visser black holes, and corresponding no-horizon spacetimes agree with the EHT results of Sgr A*. Thus, these three rotating regular spacetimes and Kerr black holes are indiscernible in some parameter space, and one cannot rule out the possibility of the former being strong candidates to be astrophysical black holes.

Keywords: Rotating black holes, Astrophysical black holes
X-Ray and GeV-γ-Ray Emission Property of TeV Compact Symmetric Object PKS 1413+135 and Implication for Episodic Jet Activity. PKS 1413+135, a compact symmetric object (CSO) with a two-sided parsec-scale structure in its miniature radio morphology, is spatially associated with 4FGL J1416.1+1320 and recently detected with MAGIC telescopes. We comprehensively analyze its X-ray and gigaelectronvolt γ-ray observation data to reveal its high-energy radiation physics. It is found that the source is in a low-flux stage before MJD 58500 and experiences violent outbursts after MJD 58500 in the gigaelectronvolt band. The flux at 10 GeV varies by ~3 orders of magnitude, and the gigaelectronvolt-flux variation is accompanied by clear spectral variation, which is characterized as a soft log-parabola spectrum in the low-flux state and a hard power-law spectrum in the bright flares. The amplitude of the variability of X-rays is lower than that of γ-rays, and no correlation of variability between γ-rays and X-rays is observed. Fitting the broadband spectral energy distribution during a gigaelectronvolt outburst with a multi-zone leptonic model, we show that the gigaelectronvolt γ-rays are attributed to the external Compton process while the X-rays are a hybrid of several components. The predicted teraelectronvolt γ-ray flux during the gigaelectronvolt outburst is consistent with the detection of MAGIC telescopes. These results, together with its CSO radio morphology, imply that PKS 1413+135 has episodic nuclear jet activities. The weak γ-ray emission before MJD 58500 may be from its sub-parsec-/parsec-scale jet component powered by previous activities, and the violent outbursts with short timescale variability after MJD 58500 could be attributed to the recently restarted jet activity.

Keywords: Non-thermal radiation sources, Relativistic jets, Active galactic nuclei, Gamma-rays
Analysis of Thermal Emissions of Exoplanets with Axially Symmetric Temperature Gradients. Here a new method of modeling the thermal emissions of exoplanets is described, in which the temperature gradient of an exoplanet is approximated by splitting it into N zones. First, we seek to determine how much this method differs from a simple dayside-nightside model used by previous researchers and found that the difference between the N-zone and the dayside-nightside models is greatest during the primary transit of the exoplanet, and for large temperature gradients. Next, we determine under what conditions EXONEST, a Bayesian inference software package, is able to correctly determine the model used to generate synthetic light-curve data. EXONEST is best able to determine the model used to generate synthetic data when the mass of the exoplanet is known, the added noise to the data is low, and the thermal emissions are large compared to the ellipsoidal variations. Finally, EXONEST was used to analyze photometric data for exoplanets Kepler-41b and Kepler-412b, and the dayside brightness temperatures were estimated to be 2574 ± 59 and 2496 ± 64 K, and those of the nightside were estimated to be 860 ± 316 and 874 ± 333 K for Kepler-41b and Kepler-412b, respectively. Finally, we found that the hottest zone for both planets was the zone nearest the terminator on the dayside of the exoplanet. This surprising result suggests that the model is better applied to exoplanets with little to no heat recirculation.

Keywords: Nested sampling, Exoplanets
Study of X-Ray Intraday Variability of HBL Blazars Based on Observations Obtained with XMM-Newton. We present an extensive study on the X-ray intraday variability of 10 teraelectronvolt-emitting high synchrotron peaked blazars (HBLs): 1ES 0229+200, 1ES 0414+009, PKS 0548-322, 1ES 1101-232, 1H 1219+301, H 1426+428, Mrk 501, 1ES 1959+650, PKS 2005-489, and 1ES 2344+514 made with 25 XMM-Newton pointed observations during its operational period. Intraday variability has been estimated in three energy bands: soft (0.3-2 keV), hard (2-10 keV), and total (0.3-10 keV). Although seven out of 10 teraelectronvolt HBLs exhibited some intraday variability at 3σ levels, no major variations exceeding 6% were detected. We explored the spectral properties of the sample by extracting the hardness ratio from the soft and hard bands; no significant variations in the hardness ratio were observed in any source. We performed power spectral density analyses on the variable light curves by fitting power laws, yielding slopes lying in the range of 1.11-2.93 for different HBLs. We briefly discuss possible emission mechanisms and carry out rough estimates for magnetic fields, electron Lorentz factors, and emission region sizes for seven of these HBLs.

Keywords: Timing variation methods, Blazars, X-ray active galactic nuclei, BL Lacertae objects
Dynamical Disruption Timescales and Chaotic Behavior of Hierarchical Triple Systems. We examine the stability of hierarchical triple systems using direct N-body simulations without adopting a secular perturbation assumption. We estimate their disruption timescales in addition to the mere stable/unstable criterion, with particular attention to the mutual inclination between the inner and outer orbits. First, we improve the fit to the dynamical stability criterion by Mardling &amp; Aarseth widely adopted in the previous literature. Especially, we find that that the stability boundary is very sensitive to the mutual inclination; coplanar retrograde triples and orthogonal triples are much more stable and unstable, respectively, than coplanar prograde triples. Next, we estimate the disruption timescales of triples satisfying the stability condition up to 109 times the inner orbital period. The timescales follow the scaling predicted by Mushkin &amp; Katz, especially at high e out where their random walk model is most valid. We obtain an improved empirical fit to the disruption timescales, which indicates that the coplanar retrograde triples are significantly more stable than the previous prediction. We furthermore find that the dependence on the mutual inclination can be explained by the energy transfer model based on a parabolic encounter approximation. We also show that the disruption timescales of triples are highly sensitive to tiny changes of the initial parameters, reflecting the genuine chaotic nature of the dynamics of those systems.

Keywords: Multiple stars, Compact binary stars, Orbital evolution, Celestial mechanics, Three-body problem
Far-ultraviolet Flares on Accreting Protostars: Weak and Classical T Tauri Stellar Pair Analysis. The far-ultraviolet (FUV) emission of classical T Tauri stars (CTTSs) is known to play an important role in protoplanetary disk dispersal and giant planet formation, yet the role played by protostellar flares in these processes is largely unknown. We use nearby star-forming regions as laboratories to probe the FUV flare characteristics of CTTSs and test whether flares may be masked underneath accretion luminosity. Using AD Leo as our archetypal flare template, we pilot a novel analysis technique on three weak-lined T Tauri star (WTTS) and CTTS pairs: TWA-7/TWA Hya, RECX-1/RECX-11, and LkCa19/GM Aur. We find that flares contribute an upper limit of 0.064% ± 0.002%, 3.1% ± 0.1%, and 2.7% ± 0.3% to the total FUV energy budgets of TW Hya, RECX-11, and GM Aur, respectively. We also present predicted CTTS flare rates, which suggest that we would expect to observe roughly one 5σ flare on each of the CTTS archival light curves. We find one 5σ flare on TW Hya with E(1380-1745 Å) = (6.1 ± 0.7) × 1031 erg, but none are found on RECX-11 or GM Aur. Longer monitoring campaigns are required to provide more concrete constraints on the FUV flare frequency of accreting protostars. Optical TESS data of the targets were also analyzed to contextualize these results. Lastly, we report the first FUV flare on a WTTS (RECX-1), which is also the most energetic FUV flare event observed with the Hubble Space Telescope to date with E(1135-1429 Å) = (2.1 ± 0.1) × 1032 erg.

Keywords: Hubble Space Telescope, Weak-line T Tauri stars, Ultraviolet astronomy, T Tauri stars, Classical T Tauri stars
Implications from the Velocity Profile of the M87 Jet: A Possibility of a Slowly Rotating Black Hole Magnetosphere. Motivated by the measured velocity profile of the M87 jet using the Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) by Park et al. indicating that the starting position of the jet acceleration is farther from the central engine of the jet than predicted in general relativistic magnetohydrodynamic simulations, we explore how to mitigate the apparent discrepancy between the simulations and the KaVA observation. We use a semi-analytic jet model proposed by Tomimatsu &amp; Takahashi consistently solving the transmagnetic field structure but neglecting any dissipation effects. By comparing the jet model with the observed M87 jet velocity profile, we find that the model can reproduce the logarithmic feature of the velocity profile and can fit the observed data when choosing c/(100r  g ) ≲ Ω F  ≲ c/(70r  g ), where r  g  is the gravitational radius. While a total specific energy ( ${ \mathcal E }$ ) of the jet changes the terminal bulk Lorentz factor of the jet, a slower angular velocity of the black hole magnetosphere (Ω F ) makes a light-cylinder radius (r lc) larger, and it consequently pushes out a location of a starting point of the jet acceleration. Using the estimated Ω F  we further estimate the magnetic field strength on the event horizon scale in M87 by assuming Blandford-Znajek process is in action. The corresponding magnetic flux threading the event horizon of M87 is in good agreement with a magnetically arrested disk regime.

Keywords: Black hole physics, Magnetohydrodynamics, Radio jets, Relativistic jets, Active galaxies
Complex Organic Molecules Detected in 12 High-mass Star-forming Regions with Atacama Large Millimeter/submillimeter Array. Recent astrochemical models and experiments have explained that complex organic molecules (COMs; molecules composed of six or more atoms) are produced on the dust grain mantles in cold and dense gas in prestellar cores. However, the detailed chemical processes and the roles of physical conditions on chemistry are still far from understood. To address these questions, we investigated 12 high-mass star-forming regions using Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observations. They are associated with 44/95 GHz class I and 6.7 GHz class II CH3OH masers, indicative of undergoing active accretion. We found 28 hot cores with COM emission among 68 continuum peaks at 1.3 mm and specified 10 hot cores associated with 6.7 GHz class II CH3OH masers. Up to 19 COMs are identified including oxygen- and nitrogen-bearing molecules and their isotopologues in cores. The derived abundances show a good agreement with those from other low- and high-mass star-forming regions, implying that the COM chemistry is predominantly set by the ice chemistry in the prestellar core stage. One clear trend is that the COM detection rate steeply grows with the gas column density, which can be attributed to the efficient formation of COMs in dense cores. In addition, cores associated with a 6.7 GHz class II CH3OH maser tend to be enriched with COMs. Finally, our results suggest that the enhanced abundances of several molecules in our hot cores could be originated by the active accretion as well as different physical conditions of cores.

Keywords: Interstellar molecules, Massive stars, Chemical abundances, Astrochemistry, Star formation, Interstellar masers
Ion Kinetics of Plasma Flows: Earth's Magnetosheath versus Solar Wind. Revealing the formation, dynamics, and contribution to plasma heating of magnetic field fluctuations in the solar wind is an important task for heliospheric physics and for a general plasma turbulence theory. Spacecraft observations in the solar wind are limited to spatially localized measurements, so that the evolution of fluctuation properties with solar wind propagation is mostly studied via statistical analyses of data sets collected by different spacecraft at various radial distances from the Sun. In this study we investigate the evolution of turbulence in the Earth's magnetosheath, a plasma system sharing many properties with the solar wind. The near-Earth space environment is being explored by multiple spacecraft missions, which may allow us to trace the evolution of magnetosheath fluctuations with simultaneous measurements at different distances from their origin, the Earth's bow shock. We compare ARTEMIS and Magnetospheric Multiscale (MMS) Mission measurements in the Earth magnetosheath and Parker Solar Probe measurements of the solar wind at different radial distances. The comparison is supported by three numerical simulations of the magnetosheath magnetic and plasma fluctuations: global hybrid simulation resolving ion kinetic and including effects of Earth's dipole field and realistic bow shock, hybrid and Hall-MHD simulations in expanding boxes that mimic the magnetosheath volume expansion with the radial distance from the dayside bow shock. The comparison shows that the magnetosheath can be considered as a miniaturized version of the solar wind system with much stronger plasma thermal anisotropy and an almost equal amount of forward and backward propagating Alfvén waves. Thus, many processes, such as turbulence development and kinetic instability contributions to plasma heating, occurring on slow timescales and over large distances in the solar wind, occur more rapidly in the magnetosheath and can be investigated in detail by multiple near-Earth spacecraft.

Keywords: Interplanetary turbulence, Solar wind
The 3.3 μm Infrared Emission Feature Profile in HD 44179. HD 44179 is a postasymptotic giant branch star with a biconical nebula known as the Red Rectangle. It shows the 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 μm infrared emission features (commonly known as the polycyclic aromatic hydrocarbon (PAH) emission bands and the Aromatic Infrared Bands). Previous observations of HD 44179 showed that the width of the 3.3 μm emission feature was narrower within 2″ of HD 44179 and wider further away from the star. This was interpreted as an indication that the 3.3 μm emission feature arises from two types of PAHs with spatially varying relative abundances. With new observations of HD 44179 taken with the NASA Infrared Telescope Facility we find that the width of the 3.3 μm emission feature profile is not narrower on HD 44179 and conclude that there is no evidence for two spatially varying components.

Keywords: Infrared astronomy, Asymptotic giant branch stars, Polycyclic aromatic hydrocarbons, Bipolar nebulae
X-Ray Spectra from Weakly Magnetized Accretion Flows. In this paper, we expand upon previous work that argued for the possibility of a subequipartition magnetic field in the accretion flow of a black hole binary system. Using X-ray observations of the three well-known sources A0620-00, XTE J1118+480, and V404 Cyg during the quiescent state, we compare the theoretically expected spectral shape with the observed data in order to verify that the parameters of the subequipartition model are plausible. In all three cases, we find that it is possible to reproduce the spectral shape of the X-ray observations with a subequipartition flow. These findings support the idea that the quiescent state spectrum of X-ray binary systems is produced by a weakly magnetized accretion flow. A subequipartition flow would pose a significant challenge to our current understanding of jet launching, which relies on the presence of a strong magnetic field to power the jet.

Keywords: X-ray binary stars, Jets, Stellar mass black holes, Magnetic fields
Broadband X-Ray Spectral Analysis of the Dual AGN System Mrk 739. We present the result of a broadband (0.5-70 keV) X-ray spectral analysis of the late-merger galaxy Mrk 739, which contains a dual active galactic nucleus (AGN), Mrk 739E and Mrk 739W, with a separation of ≈3.4 kpc. The spectra obtained with NuSTAR, Chandra, XMM-Newton, and Swift/BAT are simultaneously analyzed by separating the contributions from the two AGNs and extended emission with the Chandra data. To evaluate the reflection components from the AGN tori, we consider two models, a phenomenological one (pexrav and zgauss) and a more physically motivated one (XCLUMPY). On the basis of the results with XCLUMPY, we find that the AGNs in Mrk 739E and Mrk 739W have intrinsic 2-10 keV luminosities of 1.0 × 1043 and 7.5 × 1041 erg s-1 absorbed by hydrogen column densities of N H &lt; 6.5 × 1019 cm-2 and ${N}_{{\rm{H}}}={6.9}_{-1.7}^{+3.2}\times {10}^{21}\ {\mathrm{cm}}^{-2}$ , respectively. The torus-covering fraction of the material with N H &gt; 1022cm-2 in Mrk 739E, ${C}_{{\rm{T}}}^{(22)}\lt 0.50$ at a 90% confidence limit, is found to be smaller than those found for late-merger ultra/luminous infrared galaxies, ${C}_{{\rm{T}}}^{(22)}=0.71\pm 0.16$ (mean and standard deviation). Considering the small star formation rate of Mrk 739E, we suggest that the gas-to-mass ratio of the host galaxy is an important parameter to determine the circumnuclear environment of an AGN in a late merger.

Keywords: Supermassive black holes, High energy astrophysics, X-ray active galactic nuclei, Active galactic nuclei, Astrophysical black holes
An Improved Calibration of the Wavelength Dependence of Metallicity on the Cepheid Leavitt Law. The Cepheid period-luminosity (PL) relation (or Leavitt law) has served as the first rung of the most widely used extragalactic distance ladder and is central to the determination of the local value of the Hubble constant (H 0). We investigate the influence of metallicity on Cepheid brightness, a term that significantly improves the overall fit of the distance ladder, to better define its wavelength dependence. To this aim, we compare the PL relations obtained for three Cepheid samples having distinct chemical composition (in the Milky Way and Magellanic Clouds) and focusing on the use of improved and recent data while covering a metallicity range of about 1 dex. We estimate the metallicity effect (hereafter γ) in 15 filters from mid-IR to optical wavelengths, including five Wesenheit indices, and we derive a significant metallicity term in all filters, in agreement with recent empirical studies and models, in the sense of metal-rich Cepheids being brighter than metal-poor ones. We describe the contribution of various systematic effects in the determination of the γ term. We find no evidence of γ changing over the wavelength range 0.5-4.5 μm, indicating that the main influence of metallicity on Cepheids is in their luminosity rather than color. Finally, we identify factors that sharpen the empirical constraints on the metallicity term over past studies, including corrections for the depth of the Magellanic Clouds, better-calibrated Cepheid photometry, improved Milky Way extinction estimates, and revised and expanded metallicity measurements in the LMC.

Keywords: Hubble constant, Metallicity, Cepheid distance
The Velocity Dispersion Function for Massive Quiescent and Star-forming Galaxies at 0.6 &lt; z ≤ 1.0. We present the first direct spectroscopic measurement of the stellar velocity dispersion function (VDF) for massive quiescent and star-forming galaxies at 0.6 &lt; z ≤ 1.0. For this analysis we use individual measurements of stellar velocity dispersion from high-signal-to-noise-ratio spectra from the public Large Early Galaxy Astrophysics Census (LEGA-C) survey. We report a remarkable stability of the VDF for both quiescent and star-forming galaxies within this redshift range, though we note the presence of weak evolution in the number densities of star-forming galaxies. We compare both VDFs with previous direct and inferred measurements at local and intermediate redshifts, with the caveat that previous measurements of the VDF for star-forming galaxies are poorly constrained at all epochs. We emphasize that this work is the first to directly push to low stellar velocity dispersion (σ ⋆ &gt; 100 km s-1) and extend to star-forming galaxies. We are largely consistent with the high-sigma tail measured from BOSS, and we find that the VDF remains constant from the median redshift of LEGA-C, z ~ 0.8, to the present day.

Keywords: Galaxy formation, Surveys, Galaxy physics, Observational cosmology, Galaxy dynamics, Stellar dynamics, Galaxy kinematics, Galaxy evolution, Galaxy counts, Galaxy spectroscopy, Galaxies, Dynamical evolution