Sazuna/UAT_keywords huggingface dataset:
Determining the Composition of Relativistic Jets from Polarization Maps. We present a stationary, axisymmetric, self-similar, semianalytic model of magnetically dominated jet plasma based on force-free regions of a relativistic magnetohydrodynamic simulation. We use this model to illustrate how the composition of relativistic jet plasma can be determined, with special attention to the example of M87. In particular, we compute synthetic Stokes maps in e-e+p plasmas with various positron-to-proton ratios using synchrotron emission models to scale the partial pressure of electrons and positrons that emit at the observed frequency to the magnetic pressure, taking into account Faraday rotation and conversion. The lepton-dominated models produce bilaterally asymmetric radio intensity profiles with strong linear polarization and Stokes Q and U maps that are bilaterally asymmetric (but strongly correlated across the jet axis) and antisymmetric (and sometimes anticorrelated), respectively. The hadronic models produce more centrally brightened intensity and polarization maps. Circular polarization provides the cleanest observational tool for distinguishing the plasmas, as it increases outward from the jet core and central axis for highly ionic plasma, and is suppressed for pair-dominated plasma. We find a measurable degree of circular polarization V/I of ${ \mathcal O }({10}^{-2})$ for subequipartition hadronic jet plasmas averaged over milliarcsecond scales. Our stationary model predicts that the intensity-normalized autocorrelation functions of Q and U increase and decrease with frequency, respectively, for higher plasma betas in our parameter survey. On the other hand, the autocorrelation of V is sensitive to the frequency at lower betas. Multiband polarimetric observations could therefore be used as a novel probe of the composition of jet plasma.

Keywords: Supermassive black holes, BL Lacertae objects, Quasars, Relativistic jets, Magnetic fields, Magnetohydrodynamical simulations
Sensitivity of the Atmospheric Water Cycle within the Habitable Zone of a Tidally Locked, Earth-like Exoplanet. Synchronously orbiting, tidally locked exoplanets with a dayside facing their star and a permanently dark nightside orbiting dim stars are prime candidates for habitability. Simulations of these planets often show the potential to maintain an Earth-like climate with a complete hydrological cycle. Here we examine the sensitivity of the atmospheric water cycle to changes in stellar flux and describe the main underlying mechanisms. In a slowly rotating, tidally locked Earth-like atmospheric model, the response to a small (about 10%) increase in stellar irradiance from a habitable zone control simulation is examined. The water cycle is enhanced in response to the increased stellar irradiance. While the evaporation increase behaves similarly to the stellar radiation increase, the day-to-night energy transport by the mean circulation is critical to the planet's precipitation changes. Increased efficiency of the energy transport in a warmer climate shapes the substellar precipitation increase. On the nightside, precipitation changes are weak as a result of the large cancellation between the increased energy transport and the increased longwave emission. The day-to-night energy transport efficiency is sensitive to the variation of the atmosphere's vertical stratification. Due to weak temperature gradients in the upper troposphere and a moist adiabat maintained in the substellar region, variations in the substellar surface temperature and specific humidity govern the increase of the planet's stratification with warming. This suggests a scaling of the nightside's precipitation based on the substellar surface thermodynamic changes, a sensitivity that holds over a wider range of stellar irradiance changes.

Keywords: Extrasolar rocky planets, Astrobiology, Exoplanet atmospheres
A Rapidly Varying Red Supergiant X-Ray Binary in the Galactic Center. We analyzed multiwavelength observations of the previously identified Galactic center X-ray binary CXO 174528.79-290942.8 (XID 6592) and determine that the near-infrared counterpart is a red supergiant based on its spectrum and luminosity. Scutum X-1 is the only previously known X-ray binary with a red supergiant donor star and closely resembles XID 6592 in terms of X-ray luminosity (LX), absolute magnitude, and IR variability (LIR,var), supporting the conclusion that XID 6592 contains a red supergiant donor star. The XID 6592 infrared counterpart shows variability of ∼0.5 mag in the Wide-field Infrared Survey Explorer-1 band (3.4 μm) on timescales of a few hours. Other infrared data sets also show large-amplitude variability from this source at earlier epochs but do not show significant variability in recent data. We do not expect red supergiants to vary by ∼50% in luminosity over these short timescales, indicating that the variability should be powered by the compact object. However, the X-ray luminosity of this system is typically ∼1000× less than the variable luminosity in the infrared and falls below the Chandra detection limit. While X-ray reprocessing can produce large-amplitude fast infrared variability, it typically requires ${L}_{{\rm{X}}}\gt \,\gt $ LIR,var to do so, indicating that another process must be at work. We suggest that this system may be a supergiant fast X-ray transient (SFXT), and that a large (∼1038 ergs s-1), fast (102-4 s) X-ray flare could explain the rapid IR variability and lack of a long-lasting X-ray outburst detection. SFXTs are normally associated with blue supergiant companions, so if confirmed, XID 6592 would be the first red supergiant SFXT, as well as the second X-ray red supergiant binary.

Keywords: X-ray astronomy, X-ray binary stars, Infrared astronomy, Infrared sources, X-ray sources, Late-type supergiant stars
The Evolution of the Broadband Temporal Features Observed in the Black-hole Transient MAXI J1820+070 with Insight-HXMT. We study the evolution of the temporal properties of MAXI J1820+070 during the 2018 outburst in its hard state from MJD 58,190 to 58,289 with Insight-HXMT in a broad energy band 1-150 keV. We find different behaviors of the hardness ratio, the fractional rms and time lag before and after MJD 58,257, suggesting a transition occurred around this point. The observed time lags between the soft photons in the 1-5 keV band and the hard photons in higher energy bands, up to 150 keV, are frequency-dependent: the time lags in the low-frequency range, 2-10 mHz, are both soft and hard lags with a timescale of dozens of seconds but without a clear trend along the outburst; the time lags in the high-frequency range, 1-10 Hz, are only hard lags with a timescale of tens of milliseconds; they first increase until around MJD 58,257 and decrease after this date. The high-frequency time lags are significantly correlated to the photon index derived from the fit to the quasi-simultaneous NICER spectrum in the 1-10 keV band. This result is qualitatively consistent with a model in which the high-frequency time lags are produced by Comptonization in a jet.

Keywords: Low-mass x-ray binary stars, Black holes, Compact objects
On the Formation of SS433. SS433 is an extraordinary X-ray binary that is ejecting bipolar jets at 26% the speed of light. Associated with the supernova-like shell W50, SS433 is also probably one of the youngest X-ray binaries with an age of ≲105 yr. However, the masses of the two components in SS433 and even the nature of the compact object are still under debate. In this work, assuming that the compact object is a black hole, we employ a binary population synthesis method to study the formation of SS433. We use previous estimates of the age of W50 and the duration of the jet activity to constrain the evolutionary history. Our calculations suggest that SS433 likely harbored a Hertzsprung gap star at the beginning of the current Roche-lobe overflow phase. The masses of the black hole and the optical/donor star in SS433 suggested by the simulations are around 8 M⊙ and 24 M⊙, respectively. Future measurement of the donor mass and radius can help infer not only the origin of the binary but also the nature of the nebula W50.

Keywords: X-ray binary stars, Black holes, Stellar evolution
A Detailed View of the Circumstellar Environment and Disk of the Forming O-star AFGL 4176. We present a detailed analysis of the disk and circumstellar environment of the forming O-type star AFGL 4176 mm1, placing results from the Atacama Large Millimeter/submillimeter Array (ALMA) into context with multiwavelength data. With ALMA, we detect seventeen 1.2 mm continuum sources within 5″ (21,000 au) of AFGL 4176 mm1. We find that mm1 has a spectral index of 3.4 ± 0.2 across the ALMA band, with &gt;87% of its 1.2 mm continuum emission from dust. The source mm2, projected 4200 au from mm1, may be a companion or a blueshifted knot in a jet. We also explore the morphological differences between the molecular lines detected with ALMA, finding 203 lines from 25 molecules, which we categorize into several morphological types. Our results show that AFGL 4176 mm1 provides an example of a forming O-star with a large and chemically complex disk, which is mainly traced by nitrogen-bearing molecules. Lines that show strong emission on the blueshifted side of the disk are predominantly oxygen-bearing, which we suggest are tracing a disk accretion shock. The molecules C34S, H2CS, and CH3CCN trace a slow wide-angle wind or dense structures in the outflow cavity walls. With the Australia Telescope Compact Array (ATCA), we detect a compact continuum source (&lt;2000 × 760 au) at 1.2 cm, associated with mm1, of which &gt;96% is from ionized gas. The ATCA NH3(1, 1) and (2, 2) emission traces a large-scale (r ∼ 0.5 pc) rotating toroid with the disk source mm1 in the blueshifted part of this structure offset to the northwest.

Keywords: Millimeter astronomy, Massive stars, Circumstellar matter, Star formation, Circumstellar disks, Radio interferometry
ALMA Observations of Giant Molecular Clouds in M33. I. Resolving Star Formation Activities in the Giant Molecular Filaments Possibly Formed by a Spiral Shock. We report molecular line and continuum observations toward one of the most massive giant molecular clouds (GMCs), GMC-16, in M33 using ALMA with an angular resolution of 0"44 × 0"27 (∼2 pc × 1 pc). We have found that the GMC is composed of several filamentary structures in 12CO and 13CO(J = 2-1). The typical length, width, and total mass are ∼50-70 pc, ∼5-6 pc, and ∼105 M⊙, respectively, which are consistent with those of giant molecular filaments (GMFs) as seen in the Galactic GMCs. The elongations of the GMFs are roughly perpendicular to the direction of the galaxy's rotation, and several H II regions are located at the downstream side relative to the filaments with an offset of ∼10-20 pc. These observational results indicate that the GMFs are considered to be produced by a galactic spiral shock. The 1.3 mm continuum and C18O(J = 2-1) observations detected a dense clump with the size of ∼2 pc at the intersection of several filamentary clouds, which is referred to as the "hub filament," possibly formed by a cloud-cloud collision. A strong candidate for protostellar outflow in M33 has also been identified at the center of the clump. We have successfully resolved the parsec-scale local star formation activity in which the galactic scale kinematics may induce the formation of the parental filamentary clouds.

Keywords: Local Group, Giant molecular clouds, Triangulum Galaxy, Star formation, Interstellar medium, Protostars
Seeds of Life in Space (SOLIS). IX. Chemical Segregation of SO<SUB>2</SUB> and SO toward the Low-mass Protostellar Shocked Region of L1157. We present observations of SO and SO2 lines toward the shocked regions along the L1157 chemically rich outflow, taken in the context of the Seeds of Life in Space IRAM Northern Extended Millimeter Array Large Program, and supported by data from the Submillimeter Array and IRAM-30 m telescope at 1.1-3.6 mm wavelengths. We simultaneously analyze, for the first time, all of the brightest shocks in the blueshifted lobe, namely, B0, B1, and B2. We found the following. (1) SO and SO2 may trace different gas, given that the large(-scale) velocity gradient analysis indicates for SO2 a volume density ( ${10}^{5}\mbox{--}{10}^{6}\,{\mathrm{cm}}^{-3}$ ) denser than that of the gas emitting in SO by a factor up to an order of magnitude. (2) Investigating the 0.1 pc scale field of view, we note a tentative gradient along the path of the precessing jet. More specifically, $\chi (\mathrm{SO}/{\mathrm{SO}}_{2})$ decreases from the B0-B1 shocks to the older B2. (3) At a linear resolution of 500-1400 au, a tentative spatial displacement between the two emitting molecules is detected, with the SO peak closer (with respect to SO2) to the position where the recent jet is impinging on the B1 cavity wall. Our astrochemical modeling shows that the SO and SO2 abundances evolve on timescales less than about 1000 years. Furthermore, the modeling requires high abundances (2 × 10-6) of both ${{\rm{H}}}_{2}{\rm{S}}/{\rm{H}}$ and S/H injected in the gas phase due to the shock occurrence, so prefrozen OCS only is not enough to reproduce our new observations.

Keywords: Star formation, Low mass stars, Interstellar medium
Estimating Dust Attenuation from Galactic Spectra. I. Methodology and Tests. We develop a method to estimate the dust attenuation curve of galaxies from full optical spectral fitting. Motivated by previous studies, we separate the small-scale features from the large-scale spectral shape, by performing a moving average method to both the observed spectrum and the simple stellar population (SSP) model spectra. The intrinsic dust-free model spectrum is then derived by fitting the observed ratio of the small- to large-scale (S/L) components with the S/L ratios of the SSP models. The selective dust attenuation curve is then determined by comparing the observed spectrum with the dust-free model spectrum. One important advantage of this method is that the estimated dust attenuation curve is independent of the shape of theoretical dust attenuation curves. We have done a series of tests on a set of mock spectra covering wide ranges of stellar age and metallicity. We show that our method is able to recover the input dust attenuation curve accurately, although the accuracy depends slightly on the signal-to-noise ratio of the spectra. We have applied our method to a number of edge-on galaxies with obvious dust lanes from the ongoing MaNGA survey, deriving their dust attenuation curves and E(B - V) maps, as well as dust-free images in g, r, and I bands. These galaxies show obvious dust lane features in their original images, which largely disappear after we have corrected the effect of dust attenuation. The vertical brightness profiles of these galaxies become axisymmetric and can well be fitted by a simple disk vertical structure model.

Keywords: Sky surveys, Galaxy processes, Stellar populations, Interstellar dust extinction, Interstellar absorption, Dust continuum emission, Spectral energy distribution, Interstellar medium, Spectroscopy, Extragalactic astronomy, Galaxy evolution, Galaxies
Blasts from the Past: Supernova Shock Breakouts among X-Ray Transients in the XMM-Newton Archive. The first electromagnetic signal from a supernova (SN) is released when the shock crosses the progenitor surface. This shock breakout (SBO) emission provides constraints on progenitor and explosion properties. Observationally, SBOs appear as minute- to hour-long extragalactic X-ray transients. They are challenging to detect and only one SBO has been observed to date. Here, we search the XMM-Newton archive and find 12 new SN SBO candidates. We identify host galaxies to nine of these at estimated redshifts of 0.1-1. The SBO candidates have energies of ∼1046 erg, timescales of 30-3000 s, and temperatures of 0.1-1 keV. They are all consistent with being SN SBOs, but some may be misidentified Galactic foreground sources or other extragalactic objects. SBOs from blue supergiants agree well with most of the candidates. However, a few could be SBOs from Wolf-Rayet stars surrounded by dense circumstellar media, whereas two are more naturally explained as SBOs from red supergiants. The observations tentatively support non-spherical SBOs and are in agreement with asymmetries predicted by recent three-dimensional SN explosion simulations. eROSITA may detect ∼2 SBOs per year, which could be detected in live analyses and promptly followed up.

Keywords: Massive stars, Shocks, X-ray transient sources, Core-collapse supernovae
C IV Emission-line Properties and Uncertainties in Black Hole Mass Estimates of z ∼ 3.5 Quasars. Using a high-luminosity (Lbol ∼ 1047.5-1048.3 erg s-1), high-redshift (3.2 &lt; z &lt; 3.8) quasar sample of 19 quasars with optical and near-infrared spectroscopy, we investigate the reliability of the C IV-based black hole mass estimates (MBH). The median logarithm of the C IV- and Hβ-based MBH ratios is 0.110 dex, with a scatter of 0.647 dex. The C IV-to-Hβ BH mass differences are significantly correlated with the C IV FWHMs, blueshifts, and asymmetries. Corrections of the C IV FWHM using the blueshift and asymmetry reduce the scatter of the mass differences by ∼0.04-0.2 dex. Quasars in our sample accrete at the Eddington ratio REDD &gt; 0.3 and cover a considerable range of blueshifts, with 18/19 of the quasars showing C IV blueshifts (with the median value of 1126 km s-1) and 14/19 of the quasars showing C IV blueshifts larger than 500 km s-1. It suggests that not all quasars with high Eddington ratios show large blueshifts. The Baldwin effect between the C IV rest-frame equivalent width (REW) and the continuum luminosity at 1350 Å is not seen, likely due to the limited luminosity range of our sample. We find a lack of flux in the red wing of the composite spectrum with larger C IV blueshift and detect a higher ratio of [O III] quasars with REW[O III] &gt; 5 Å in the subsample with lower C IV blueshift. It is more likely that they are caused by the combination of the Eddington ratio and the orientation effect.

Keywords: Black hole physics, Quasars
VERITAS Discovery of VHE Emission from the Radio Galaxy 3C 264: A Multiwavelength Study. The radio source 3C 264, hosted by the giant elliptical galaxy NGC 3862, was observed with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) between 2017 February and 2019 May. These deep observations resulted in the discovery of very high energy (VHE; E &gt; 100 GeV) γ-ray emission from this active galaxy. An analysis of ∼57 hr of quality-selected live time yields a detection at the position of the source, corresponding to a statistical significance of 7.8 standard deviations above background. The observed VHE flux is variable on monthly timescales, with an elevated flux seen in 2018 observations. The VHE emission during this elevated state is well characterized by a power-law spectrum with a photon index Γ = 2.20 ± 0.27 and flux F(&gt;315 GeV) = ( $7.6\pm {1.2}_{\mathrm{stat}}\pm {2.3}_{\mathrm{syst}})\times {10}^{-13}$ cm-2 s-1, or approximately 0.7% of the Crab Nebula flux above the same threshold. 3C 264 (z = 0.0217) is the most distant radio galaxy detected at VHE, and the elevated state is thought to be similar to that of the famously outbursting jet in M87. Consequently, extensive contemporaneous multiwavelength data were acquired in 2018 at the time of the VHE high state. An analysis of these data, including Very Long Baseline Array, Very Large Array, Hubble Space Telescope, Chandra, and Swift observations in addition to the VERITAS data, is presented, along with a discussion of the resulting spectral energy distribution.

Keywords: Relativistic jets, Active galactic nuclei, High energy astrophysics
The Second Plateau in X-Ray Afterglow Providing Additional Evidence for Rapidly Spinning Magnetars as the GRB Central Engine. Evidence for the central engine of gamma-ray bursts (GRBs) has been collected in the Neil Gehrels Swift data. For instance, some GRBs show an internal X-ray plateau followed by very steep decay, which is difficult interpret within the framework of a black hole (BH) central engine, but is consistent within a rapidly spinning magnetar engine picture. The very steep decay at the end of the plateau suggests a sudden cessation of the central engine, which is explained as the collapse of a supramassive magnetar into a BH when it spins down. Here we propose that some additional evidence, such as a second X-ray plateau feature, would show up if the fallback accretion could activate the newborn BH and sufficient energy could be transferred from the newborn BH to the GRB blast wave. With a systematic data analysis for all long GRBs, we find three candidates in the Swift sample, I.e., GRBs 070802, 090111, and 120213A, whose X-ray afterglow lightcurves contain two plateaus, with the first one being an internal plateau. We find that in a fairly loose and reasonable parameter space, the second X-ray plateau data for all 3 GRBs could be interpreted with our proposed model. Future observations are likely to discover similar events, which could offer more information on the properties of the magnetar, as well as the newborn BH.

Keywords: Gamma-ray bursts
Arp 220: New Observational Insights into the Structure and Kinematics of the Nuclear Molecular Disks and Surrounding Gas. ALMA cycle 3 observations of 12CO J = 3 → 2, 13CO J = 4 → 3, SiO J = 8 → 7, and HCN J = 5 → 4 are presented. Significant extended emission is detected in 12CO J = 3 → 2 with a morphology that is indicative of m = 2 tidal features, suggesting gas inflow. In addition, outflows for both nuclei are found in 12CO J = 3 → 2. Significant SiO absorption is detected in the western nucleus. HCN that is morphologically distinct from CO is detected in both nuclei. These observations are compared to non-LTE radiative transfer models created using the Line Modeling Engine for simple gas dynamics to gain insight into how physical parameters, such as rotational velocity, turbulent velocity, gas temperature, dust temperature, and gas mass, can reproduce the observed kinematic and spatial features. The eastern nucleus is found to be best modeled with an inclusion of a temperature asymmetry from one side of the disk to the other. It is also found that the western nucleus is optically thick even in the less abundant species of 13CO, absorbing significant amounts of continuum radiation.

Keywords: Ultraluminous infrared galaxies, Radiative transfer, CO line emission