Sazuna/UAT_keywords huggingface dataset:
The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope. The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area Telescope (4LAC) between 2008 August 4 and 2016 August 2 contains 2863 objects located at high Galactic latitudes (|b| &gt; 10°). It includes 85% more sources than the previous 3LAC catalog based on 4 yr of data. AGNs represent at least 79% of the high-latitude sources in the fourth Fermi-Large Area Telescope Source Catalog (4FGL), which covers the energy range from 50 MeV to 1 TeV. In addition, 344 gamma-ray AGNs are found at low Galactic latitudes. Most of the 4LAC AGNs are blazars (98%), while the remainder are other types of AGNs. The blazar population consists of 24% Flat Spectrum Radio Quasars (FSRQs), 38% BL Lac-type objects, and 38% blazar candidates of unknown types (BCUs). On average, FSRQs display softer spectra and stronger variability in the gamma-ray band than BL Lacs do, confirming previous findings. All AGNs detected by ground-based atmospheric Cerenkov telescopes are also found in the 4LAC.

Keywords: BL Lacertae objects, Quasars, Gamma-ray sources, Blazars, Relativistic jets, Active galactic nuclei
Exploring Bistability in the Cycles of the Solar Dynamo through Global Simulations. The calling card of solar magnetism is the sunspot cycle, during which sunspots regularly reverse their polarity sense every 11 yr. However, a number of more complicated time-dependent behaviors have also been identified. In particular, there are temporal modulations associated with active longitudes and hemispheric asymmetry, when sunspots appear at certain solar longitudes or else in one hemisphere preferentially. So far, a direct link between this asymmetric temporal behavior and the underlying solar dynamo has remained elusive. In this work, we present results from global 3D magnetohydrodynamic simulations, which display both behavior reminiscent of the sunspot cycle (regular polarity reversals and equatorward migration of internal magnetic field) and asymmetric, irregular behavior which we interpret as active longitudes and hemispheric asymmetry in the simulations. The simulations are thus bistable, in that the turbulent convection can stably support two distinct flavors of magnetism at different times, in superposition or with smooth transitions from one state to the other. We discuss this new family of dynamo models in the context of the extensive observations of the Sun's surface magnetic field with the Solar and Heliospheric Observatory and the Solar Dynamics Observatory, as well as earlier observations of sunspot number and synoptic maps. We suggest that the solar dynamo itself may be bistable in nature, exhibiting two types of temporal behavior in the magnetic field.

Keywords: Solar interior, Solar convective zone, Solar dynamo, Solar magnetic fields, Magnetohydrodynamical simulations
Study of the Decay Rates of the Umbral Area of Sunspot Groups Using a High-resolution Database. The emergence and decay of the sunspot groups are important components of the solar dynamo models. There are two different types of studies on the evolution of active regions. One of them is based on fewer data with higher spatial resolution, the other one uses more data with lower spatial resolution. The input data of the present study allow the investigation with high resolution both spatially and temporally. The temporal resolution of the Solar and Heliospheric Observatory Debrecen sunspot database is one and a half hours, and it also makes it possible to identify all individual sunspots with the position, area, and magnetic polarity. More than 200 sunspot groups have been selected, which have clear maxima on the solar disk, and the decrease of their umbral area is observable during at least four days. The decay rates were calculated by using two data: the umbral area and the number of contained sunspots - these decay rates were computed for the total umbral area of sunspot groups and their leading and following parts. The decay rate has a linear area dependency, and it is higher for the following part than for the leading one.

Keywords: Sunspots, Sunspot groups
Iron Line Tomography of General Relativistic Hydrodynamic Accretion around Kerr Black Holes. We consider a temporal response of relativistically broadened line spectrum of iron from black hole accretion irradiated by an X-ray echo under strong gravity. The physical condition of accreting gas is numerically calculated in the context of general relativistic hydrodynamics under steady-state axisymmetry in Kerr geometry. With the onset of a point-like X-ray flare of a short finite duration just above the accretion surface, the gas is assumed to be ionized to produce a neutral iron fluorescent line. Using a fully relativistic ray-tracing approach, the response of line photons due to the X-ray illumination is traced as a function of time and energy for different source configurations around Schwarzschild and Kerr black holes. Our calculations show that the X-ray echo on the accretion surface clearly imprints a characteristic time-variability in the line spectral features depending on those parameters. Simulated line profiles, aimed for the future microcalorimeter missions of large collecting area such as Athena/X-IFU for typical radio-quiet Seyfert galaxies, are presented to demonstrate that state-of-the-art new observations could differentiate various source parameters by such an X-ray tomographic line reverberation.

Keywords: Accretion, Black hole physics, Computational astronomy, High energy astrophysics, Hydrodynamics, Relativity, Seyfert galaxies, Active galactic nuclei
Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions. The protagonists of the last great phase transition of the universe - cosmic reionization - remain elusive. Faint star-forming galaxies are leading candidates because they are found to be numerous and may have significant ionizing photon escape fractions (fesc). Here we update this picture via an empirical model that successfully predicts latest observations (e.g., the rapid drop in star-formation density (ρSFR at z &gt; 8). We generate an ionizing spectrum for each galaxy in our model and constrain fesc by leveraging latest measurements of the reionization timeline (e.g., Lyα damping of quasars and galaxies at z &gt; 7). Assuming a constant fesc across all sources at z &gt; 6, we find MUV &lt; -13.5 galaxies need fesc = 0.21-0.04+0.06 to complete reionization. The inferred Intergalactic Medium neutral fraction is [0.9, 0.5, 0.1] at z=[8.2,6.8,6.2] ± 0.2 - that is, the bulk of reionization transpires rapidly in 300 Myr, driven by the z &gt; 8 ρSFR and favored by high neutral fractions (∼60%-90%) measured at z ∼ 7-8. Inspired by the emergent sample of Lyman Continuum (LyC) leakers spanning z ∼ 0-6.6 that overwhelmingly displays higher-than-average star-formation surface density (ΣSFR), we propose a physically motivated model relating fesc to ΣSFR and find fesc ∝ ΣSFR0.4±0.1. Since ΣSFR falls by ∼2.5 dex between z = 8 and z = 0, our model explains the humble upper limits on fesc at lower redshifts and its required evolution to fesc ∼ 0.2 at z &gt; 6. Within this model, strikingly, &lt;5% of galaxies with MUV &lt; -18 and log(M⋆/M⊙) &gt; 8 (the "oligarchs") account for ≳80% of the reionization budget - a stark departure from the canonical "democratic" reionization led by copious faint sources. In fact, faint sources (MUV &gt; -16) must be relegated to a limited role in order to ensure high neutral fractions at z = 7-8. Shallow faint-end slopes of the UV luminosity function (αUV &gt; -2) and/or fesc distributions skewed toward massive galaxies produce the required late and rapid reionization. We predict that LyC leakers like COLA1 (z = 6.6, fesc ∼ 30%, MUV = -21.5) will become increasingly common toward z ∼ 6 and that the drivers of reionization do not lie hidden across the faint end of the luminosity function but are already known to us.

Keywords: Early universe, Observational cosmology, Cool intergalactic medium, Lyman-alpha galaxies, Galaxy evolution, Intergalactic medium, Extragalactic astronomy, Reionization
A 3D Radiation Hydrodynamic AGB Binary Model. The origin of chemically peculiar stars and nonzero eccentricity in evolved close binaries have been long-standing problems in binary stellar evolution. Answers to these questions may trace back to an intense mass transfer during the asymptotic-giant-branch (AGB) binary phase. In this work, we use AstroBEAR to solve the 3D radiation hydrodynamic equations and calculate the mass transfer rate in AGB binaries that undergo the wind-Roche-lobe overflow or Bondi-Hoyle-Lyttleton (BHL) accretion. MESA produces the density and temperature of the boundary condition of the AGB star. To improve the resolution of the dynamics of a circumbinary disk, we implement an azimuthal angle dependent 3D radiation transfer. We consider optically thin cooling and obtain the number density of the coolants by solving Saha equations. One of the goals of this work is to illustrate the transition from the wind-Roche-lobe overflow to BHL accretion. Both circumbinary disks and spiral structure outflows can appear in the simulations. Circumbinary disks may form when the optical thickness in the equatorial region increases. The increase of the optical thickness is due to the deflected wind. The resulting mass transfer efficiency in our models is up to a factor of 8 times higher than what the standard BHL accretion scenario predicts, and the outflow gains up to 91% of its initial angular momentum when it reaches 1.3 binary separations. Consequently, some AGB binaries may undergo orbit shrinkage, and some will expand. The high mass transfer efficiency is closely related to the presence of the circumbinary disks.

Keywords: Hydrodynamics, Symbiotic binary stars, Asymptotic giant branch, Stellar winds
Dust-depleted Inner Disks in a Large Sample of Transition Disks through Long-baseline ALMA Observations. Transition disks with large inner dust cavities are thought to host massive companions. However, the disk structure inside the companion orbit and how material flows toward an actively accreting star remain unclear. We present a high-resolution continuum study of inner disks in the cavities of 38 transition disks. Measurements of the dust mass from archival Atacama Large Millimeter/Submillimeter Array observations are combined with stellar properties and spectral energy distributions to assemble a detailed picture of the inner disk. An inner dust disk is detected in 18 of 38 disks in our sample. Of the 14 resolved disks, 8 are significantly misaligned with the outer disk. The near-infrared excess is uncorrelated with the mm-dust mass of the inner disk. The size-luminosity correlation known for protoplanetary disks is recovered for the inner disks as well, consistent with radial drift. The inner disks are depleted in dust relative to the outer disk, and their dust mass is uncorrelated with the accretion rates. This is interpreted as the result of radial drift and trapping by planets in a low α (∼10-3) disk, or a failure of the α-disk model to describe angular momentum transport and accretion. The only disk in our sample with confirmed planets in the gap, PDS 70, has an inner disk with a significantly larger radius and lower inferred gas-to-dust ratio than other disks in the sample. We hypothesize that these inner disk properties and the detection of planets are due to the gap having only been opened recently by young, actively accreting planets.

Keywords: Astrophysical dust processes, Star formation, Protoplanetary disks, Stellar accretion disks, Circumstellar dust, Planet formation
A Classification Algorithm for Time-domain Novelties in Preparation for LSST Alerts. Application to Variable Stars and Transients Detected with DECam in the Galactic Bulge. With the advent of the Legacy Survey of Space and Time, time-domain astronomy will be faced with an unprecedented volume and rate of data. Real-time processing of variables and transients detected by such large-scale surveys is critical to identifying the more unusual events and allocating scarce follow-up resources efficiently. We develop an algorithm to identify these novel events within a given population of variable sources. We determine the distributions of magnitude changes (dm) over time intervals (dt) for a given passband f, pf({dm}| {dt}), and use these distributions to compute the likelihood of a test source being consistent with the population or being an outlier. We demonstrate our algorithm by applying it to the DECam multiband time-series data of more than 2000 variable stars identified by Saha et al. in the Galactic Bulge that are largely dominated by long-period variables and pulsating stars. Our algorithm discovers 18 outlier sources in the sample, including a microlensing event, a dwarf nova, and two chromospherically active RS CVn stars, as well as sources in the blue horizontal branch region of the color-magnitude diagram without any known counterparts. We compare the performance of our algorithm for novelty detection with the multivariate Kernel Density Estimator and Isolation Forest on the simulated PLAsTiCC data set. We find that our algorithm yields comparable results despite its simplicity. Our method provides an efficient way for flagging the most unusual events in a real-time alert-broker system.

Keywords: Astronomy databases, Surveys, Astrostatistics, Time domain astronomy, Variable stars, Algorithms, Catalogs
Properties of Short GRB Pulses in the Fourth BATSE Catalog: Implications for the Structure and Evolution of the Jetted Outflows. Considering the shortage of comparative studies on pulse temporal characteristics between single-peaked short gamma-ray bursts (sGRBs) and double-peaked sGRBs, we examine the pulse properties of a sample of 100 BATSE sGRBs using the BATSE Time-Tagged Event data with a 5 ms resolution. A total of 243 individual pulses of the single-peaked, double-peaked, and triple-peaked sGRBs are fitted to find statistical properties such as the pulse asymmetry, amplitude, peak time, and pulse width, etc. For the double-peaked sGRBs, according to the overlapping ratio between two adjacent peaks, we first define two kinds of double-peaked sGRBs as M-loose and M-tight types and find that most of the first pulses are similar to the single-peaked ones. We study the dependence of the FWHM on the photon energy among different energy bands. Interestingly, it is found that a power-law relation with an index of -0.4 does exist between the FWHM and the photon energy for the single- and double-peaked sGRBs. More interestingly, we notice that the power-law relation with a positive index also exists for several special short bursts. In view of the three typical timescales of pulses, namely the angular spreading timescale, the dynamic timescale, and the cooling timescale, we propose that the diverse power-law indexes together with the profile evolution of the GRB pulse can be used as an effective probe to diagnose the structure and evolution of the relativistically jetted outflows.

Keywords: Gamma-ray bursts
Transport of High-energy Charged Particles through Spatially Intermittent Turbulent Magnetic Fields. Identifying the sources of the highest energy cosmic rays requires understanding how they are deflected by the stochastic, spatially intermittent intergalactic magnetic field. Here we report measurements of energetic charged-particle propagation through a laser-produced magnetized plasma with these properties. We characterize the diffusive transport of the particles experimentally. The results show that the transport is diffusive and that, for the regime of interest for the highest energy cosmic rays, the diffusion coefficient is unaffected by the spatial intermittency of the magnetic field.

Keywords: High energy astrophysics, Laboratory astrophysics, Plasma astrophysics, Intergalactic medium, Particle astrophysics, Magnetic fields, Ultra-high-energy cosmic radiation
In Situ Observations of Interplanetary Dust Variability in the Inner Heliosphere. This work examines the variation of interplanetary dust count rates and directionality during the first three solar encounters made by the Parker Solar Probe spacecraft, covering distances between 0.65 au (∼140 solar radii, RS) and 0.16 au (∼35 RS). Dust detections are made by the FIELDS instrument via plasma clouds, produced by impact ionization of dust grains on spacecraft surfaces and resultant spacecraft potential perturbations. Dust count rates and inferred densities are found to vary by ∼50% between the three solar encounters (∼5 months per orbit), with most of the variation concentrated below 0.23 au (∼50RS). Dust count rates and directionality, as well as the encounter-to-encounter variability in both quantities are found to be consistent with β-meteoroids: dust grains exiting the solar system on hyperbolic trajectories. Interpretation of the the dust count rate data and the dust directionality data independently suggest (I) that the β-meteoroid source region is more complex than preliminary models suggest, and (II) that the primary β-meteoroid source region is approximately located between 10 and 30 solar radii from the Sun. These data offer important clues as to the location and geometry of the β-meteoroid source region, and consequently clues about the collisional and sublimation processing of interplanetary dust grains near the Sun.

Keywords: Zodiacal cloud, Interplanetary dust, Heliosphere
On the Jet Production Efficiency in a Sample of the Youngest Radio Galaxies. Here we discuss the jet production efficiency in a sample of 17 young radio galaxies with measured redshifts, kinematic ages, and nuclear X-ray fluxes, for which the observed luminosities of compact jets/lobes and accretion disks correspond to the same episode of AGN activity. For the targets, we analyze the available optical data, estimating the bolometric luminosities of the accretion disks Lbol, and the black hole masses; we also derive the minimum jet kinetic luminosities, Pj. With this information we investigate the distribution of our sample in the three-dimensional space of the accretion rate λEdd &amp;Congruent Lbol/LEdd, the nuclear X-ray luminosity LX considered here as a limit for the emission of the disk coronae, and Pj, expressing the latter two parameters either in the Eddington units, or in the units of the disk luminosity. We find that (I) the accretion rate λEdd in our sample is distributed within a narrow range λEdd ∼ 0.01-0.2; (II) the normalized jet power Pj/LEdd formally correlates with the accretion rate λEdd, with some saturation at the largest values λEdd &gt; 0.05; (III) the jet production efficiency ηjet ≡ Pj/\dot{M}acc c2 spans a range from ηjet ≲ 10-3 up to ∼0.2 at maximum, which is below the level expected for magnetically arrested disks around maximally spinning black holes; and (IV) there is a diversification in ηjet on the hardness-intensity diagram LX/Lbol - λEdd, with the jets being produced most efficiently during the high/hard states, and suppressed during the soft states.

Keywords: Radio jets, Emission line galaxies, Radio galaxies, Active galactic nuclei, Non-thermal radiation sources, X-ray sources, Radio continuum emission
A Feature Representation Method for X-Ray Pulsar Signals Based on Cyclostationarity Theory. X-ray pulsar signals commonly have a very low amplitude and suffer from high observation noise and statistical correlation interference, which seriously degrade the signal detection performance given finite observation times. Here, noise refers to the uncertainty distribution of the photon Poisson statistics, and interference refers to time-dependent broadband or narrowband signals, which may originate from some artificial interference source or other pulsars. To address the above problems, this paper proposes a feature representation method for pulsar signal detection based on high-order cyclostationarity theory. First, we establish a photon signal model of an X-ray detector based on the cyclostationary characteristics of pulsar signals, considering period jitter, correlation interference, and Gaussian noise in the pulsar emission process. By introducing cyclic statistics, we use a direct estimation method for the high-order spectrum, including a nonuniform sampling strategy, to accurately extract signal features and effectively suppress correlation interference and noise. Finally, we use simulation data and Rossi X-ray Timing Explorer observation data to verify the proposed method. The results show that the proposed method is a promising feature modeling solution that is superior to traditional one-dimensional spectra and epoch folding in counteracting interference and noise. While such feature modeling is particularly useful for applications such as pulsar navigation, we believe that this method has general promise for a wide range of pulsar-related research.

Keywords: Astronomy data modeling, Astronomy data analysis, Rotation powered pulsars, X-ray stars
Measuring the AGN Sublimation Radius with a New Approach: Reverberation Mapping of Broad Line Polarization. Here we give an observational method for measurements of the equatorial scattering region radius using variability in the polarized broad lines in Type 1 active galactic nuclei (AGNs). The polarization in broad lines of Type 1 AGNs is mostly caused by equatorial scattering, where specific features allow one to separate its contribution from the total polarized flux. We propose to monitor variability in the polarized line flux and find the time lag between the nonpolarized continuum and polarized broad line variability. The distance to the scattering screen can then be determined from the time delay. The method was, for the first time, applied to the observations of the Type 1 AGN Mrk 6, and we found that the size of the scattering region in this AGN is around 100 lt-days. That is significantly smaller than the dusty region size estimated by the infrared interferometric observations and also larger than known broad line region (BLR) size. This indicates that the scattering region lies between the BLR and the dusty region and could be used as a probe of the dust sublimation radius.

Keywords: Seyfert galaxies, Active galaxies, Polarimetry
Measuring the Heating and Cooling of the Interstellar Medium at High Redshift: PAH and [C II] Observations of the Same Star-forming Galaxies at z ∼ 2. Star formation depends critically on cooling mechanisms in the interstellar medium (ISM); however, thermal properties of gas in galaxies at the peak epoch of star formation (z ∼ 2) remain poorly understood. A limiting factor in understanding the multiphase ISM is the lack of multiple tracers detected in the same galaxies, such as Polycyclic Aromatic Hydrocarbon (PAH) emission, a tracer of a critical photoelectric heating mechanism in interstellar gas, and [C II] 158 μm fine-structure emission, a principal coolant. We present ALMA Band 9 observations targeting [C II] in six z ∼ 2 star-forming galaxies with strong Spitzer IRS detections of PAH emission. All six galaxies are detected in dust continuum and marginally resolved. We compare the properties of PAH and [C II] emission, and constrain their relationship as a function of total infrared luminosity (LIR) and IR surface density. [C II] emission is detected in one galaxy at high signal-to-noise (34σ), and we place a secure upper limit on a second source. The rest of our sample are not detected in [C II] likely due to redshift uncertainties and narrow ALMA bandpass windows. Our results are consistent with the deficit in [C II]/LIR and PAH/LIR observed in the literature. However, the ratio of [C II] to PAH emission at z ∼ 2 is possibly much lower than what is observed in nearby dusty star-forming galaxies. This could be the result of enhanced cooling via [O I] at high-z, hotter gas and dust temperatures, and/or a reduction in the photoelectric efficiency, in which the coupling between interstellar radiation and gas heating is diminished.

Keywords: Starburst galaxies, Ultraluminous infrared galaxies, Galaxy evolution, Interstellar medium, High-redshift galaxies, Galaxies