Sazuna/UAT_keywords huggingface dataset:
Construction of Explicit Symplectic Integrators in General Relativity. I. Schwarzschild Black Holes. Symplectic integrators that preserve the geometric structure of Hamiltonian flows and do not exhibit secular growth in energy errors are suitable for the long-term integration of N-body Hamiltonian systems in the solar system. However, the construction of explicit symplectic integrators is frequently difficult in general relativity because all variables are inseparable. Moreover, even if two analytically integrable splitting parts exist in a relativistic Hamiltonian, all analytical solutions are not explicit functions of proper time. Naturally, implicit symplectic integrators, such as the midpoint rule, are applicable to this case. In general, these integrators are numerically more expensive to solve than same-order explicit symplectic algorithms. To address this issue, we split the Hamiltonian of Schwarzschild spacetime geometry into four integrable parts with analytical solutions as explicit functions of proper time. In this manner, second- and fourth-order explicit symplectic integrators can be easily made available. The new algorithms are also useful for modeling the chaotic motion of charged particles around a black hole with an external magnetic field. They demonstrate excellent long-term performance in maintaining bounded Hamiltonian errors and saving computational cost when appropriate proper time steps are adopted.

Keywords: Black hole physics, Computational methods, Computational astronomy
A Survey of Active Galaxies at TeV Photon Energies with the HAWC Gamma-Ray Observatory. The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory continuously detects TeV photons and particles within its large field of view, accumulating every day a deeper exposure of two-thirds of the sky. We analyzed 1523 days of HAWC live data acquired over four and a half years, in a follow-up analysis of 138 nearby (z &lt; 0.3) active galactic nuclei from the Third Catalog of Hard Fermi-LAT sources culminating within 40° of the zenith at Sierra Negra, the HAWC site. This search for persistent TeV emission used a maximum-likelihood analysis assuming intrinsic power-law spectra attenuated by pair production of gamma-ray photons with the extragalactic background light. HAWC clearly detects persistent emission from Mkn 421 and Mkn 501, the two brightest blazars in the TeV sky, at 65σ and 17σ level, respectively. Marginal evidence, just above the 3σ level, was found for three other known very high-energy emitters: the radio galaxy M87 and the BL Lac objects VER J0521+211 and 1ES 1215+303, the latter two at z ∼ 0.1. We find a 4.2σ evidence for collective emission from the set of 30 previously reported very high-energy sources, with Mkn 421 and Mkn 501 excluded. Upper limits are presented for the sample under the power-law assumption and in the predefined (0.5-2.0), (2.0-8.0), and (8.0-32.0) TeV energy intervals.

Keywords: Sky surveys, Gamma-ray sources, Blazars, Radio galaxies, Active galactic nuclei, Gamma-rays
Milky Way Tomography with the SkyMapper Southern Survey. II. Photometric Recalibration of SMSS DR2. We apply the spectroscopy-based stellar-color regression (SCR) method to perform an accurate photometric recalibration of the second data release from the SkyMapper Southern Survey (SMSS DR2). From comparison with a sample of over 200,000 dwarf stars with stellar atmospheric parameters taken from GALAH+ DR3 and with accurate, homogeneous photometry from Gaia DR2, zero-point offsets are detected in the original photometric catalog of SMSS DR2, in particular for the gravity- and metallicity-sensitive uv bands. For the uv bands, the zero-point offsets are close to zero at very low extinction, and then steadily increase with E(B - V), reaching as large as 0.174 and 0.134 mag respectively, at E(B - V) ∼ 0.5 mag. These offsets largely arise from the adopted dust term in the transformations used by SMSS DR2 to construct photometric calibrators from the ATLAS reference catalog. For the gr bands, the zero-point offsets exhibit negligible variations with the E(B - V) of Schlegel et al. due to their tiny coefficients on the dust term in the transformation. Our study also reveals small but significant spatial variations of the zero-point offsets in all uvgr bands. External checks using Strömgren photometry, WD loci, and the SDSS Stripe 82 standard-star catalog independently confirm the zero-points found by our revised SCR method.

Keywords: CCD photometry, Sky surveys, Astronomy data analysis, Interstellar dust extinction, Flux calibration, Spectroscopy
New Ritz Wavelengths and Transition Probabilities of Parity-forbidden [Mn II] Lines of Astrophysical Interest. We report a comprehensive list of accurate Ritz wavelengths and calculated transition probabilities for parity-forbidden [Mn II] lines. Ritz wavelengths have been derived from experimentally established energy level values resulting from an extensive analysis of a high-resolution Fourier-transform emission spectrum of singly ionized manganese. Our analysis includes transitions between all known metastable and other long-lived levels of Mn II giving a total of 1130 [Mn II] Ritz wavelengths. Our entire list of derived Ritz wavelengths for [Mn II] lines ranges between 237 nm and 170 μm (42,125-58 cm-1). The accurate Ritz wavelengths and calculated transition probabilities for forbidden lines in this paper are useful in the study and diagnostics of nebulae and other low-density astrophysical plasmas.

Keywords: High resolution spectroscopy, Spectral line lists, Theoretical techniques, Line positions, Atomic physics, Laboratory astrophysics, Atomic spectroscopy, Atomic data benchmarking, Line intensities
Transient Formation of C<SUB>2</SUB> and CN in the Near-maximum Phase of Nova Cas 2020(=V1391 Cas). Nova Cas 2020 was a second example of a classical nova forming both C2 and CN molecules during its near-maximum phase. The formation C2 and CN is indicative of the carbon-rich (C/O &gt; 1) gas envelope of the nova. Our low-resolution spectroscopic observations in the optical from UT 2020 July 31 to August 19 revealed the appearance and the disappearance of the molecular absorption bands of C2 and CN in Nova Cas 2020. These molecules were present during ∼3 days only. Based on analysis of the C2 Swan band profiles, C2 (and probably CN also) formed at ∼5000 K in the nova envelope (see ∼8000 K for typical novae at their visual brightness maxima). Spectral evolution and the formation conditions of the molecules are similar to those of V2676 Oph, which is the first example of a C2/CN-forming nova. We predict that a late-phase grain formation episode similar to that seen in V2676 Oph will occur in Nova Cas 2020.

Keywords: DQ Herculis stars, Slow novae, Classical novae
AGN Triality of Triple Mergers: Detection of Faint X-Ray Point Sources. We present results from our X-ray analysis of a systematic search for triple active galactic nuclei (AGNs) in nearby (z &lt; 0.077) triple galaxy mergers. We analyze archival Chandra observations of seven triple galaxy mergers with BAYMAX (Bayesian Analysis of Multiple AGNs in X-rays), fitting each observation with single, dual, and triple X-ray point-source models. In doing so, we conclude that one triple merger has one X-ray point source (SDSS J0858+1822, although it is unlikely to be an AGN), five triple mergers are likely composed of two X-ray point sources (NGC 3341, SDSS J1027+1749, SDSS J1631+2352, SDSS J1708+2153, and SDSS J2356-1016), and one system is composed of three X-ray point sources (SDSS J0849+1114). By fitting the individual X-ray spectra of each point source, we analyze the 2-7 keV luminosities, as well as the levels of obscuration associated with each potential AGN. We find that 4/5 dual X-ray point-source systems have primary and secondary point sources with bright X-ray luminosities (L2-7kev &gt; 1040 erg s-1), possibly associated with four new undetected dual AGNs. The dual and triple-point-source systems are found to have physical separations between 3 and 9 kpc and flux ratios between 2 × 10-3 and 0.84. A multiwavelength analysis to determine the origin of the X-ray point sources discovered in this work is presented in our companion paper (Foord et al. 2020c).

Keywords: AGN host galaxies, Supermassive black holes, X-ray active galactic nuclei, Interacting galaxies
AGN Triality of Triple Mergers: Multiwavelength Classifications. We present results from a multiwavelength analysis searching for multiple active galactic nucleus (AGN) systems in nearby (z &lt; 0.077) triple galaxy mergers. Combining archival Chandra, Sloan Digital Data Survey (SDSS), Wide-field Infrared Survey Explorer (WISE), and Very Large Array observations, we quantify the rate of nearby triple AGNs, as well as investigate possible connections between supermassive black hole accretion and merger environments. Analyzing the multiwavelength observations of seven triple galaxy mergers, we find that one triple merger has a single AGN (NGC 3341); we discover, for the first time, four likely dual AGNs (SDSS J1027+1749, SDSS J1631+2352, SDSS J1708+2153, and SDSS J2356-1016); we confirm one triple-AGN system, SDSS J0849+1114; and one triple merger in our sample remains ambiguous (SDSS J0858+1822). Analyzing the WISE data, we find a trend of increasing NH (associated with the primary AGN) as a function of increasing W1 - W2 color, reflecting that the motions of gas and dust are coupled in merging environments, where large amounts of both can be funneled into the active central region during mergers. Additionally, we find that the one triple-AGN system in our sample has the highest levels of NH and W1 - W2 color, while the dual-AGN candidates all have lower levels; these results are consistent with theoretical merger simulations that suggest that higher levels of nuclear gas are more likely to activate AGNs in mergers.

Keywords: AGN host galaxies, Supermassive black holes, X-ray active galactic nuclei, Galaxy mergers
Pair Drizzle around Sub-Eddington Supermassive Black Holes. Electron-positron pair creation near sub-Eddington accretion rate black holes is believed to be dominated by the Breit-Wheeler process (photon-photon collisions). The interacting high-energy photons are produced when unscreened electric fields accelerate leptons either in coherent, macroscopic gaps, or in incoherent structures embedded in the turbulent plasma flow. The latter type of acceleration results in a drizzle of pair production sourced by photons from the background radiation field whose energies are near the pair-production threshold. In this work, we use radiation general relativistic magnetohydrodynamic simulations to extend an earlier study of pair drizzle by Mościbrodzka et al. We focus on low-magnetization (standard and normal evolution) accretion onto supermassive Kerr black holes and consider radiation due to synchrotron, bremsstrahlung, and Compton upscattering processes. We confirm that pair drizzle in M87 is sufficient to keep the magnetospheric charge density orders of magnitude above the Goldreich-Julian density. We also find that pair production peaks along the jet-disk boundary.

Keywords: Accretion, Black hole physics, Galactic center, Plasma astrophysics, Computational methods
Super-Eddington Mass Growth of Intermediate-mass Black Holes Embedded in Dusty Circumnuclear Disks. We perform the first three-dimensional radiation hydrodynamical simulations that investigate the growth of intermediate-mass BHs (IMBHs) embedded in massive self-gravitating, dusty nuclear accretion disks. We explore the dependence of mass accretion efficiency on the gas metallicity Z and mass injection at super-Eddington accretion rates from the outer galactic disk ${\dot{M}}_{\mathrm{in}}$ , and we find that the central BH can be fed at rates exceeding the Eddington rate only when the dusty disk becomes sufficiently optically thick to ionizing radiation. In this case, mass outflows from the disk owing to photoevaporation are suppressed, and thus a large fraction (≳40%) of the mass injection rate can feed the central BH. The conditions are expressed as ${\dot{M}}_{\mathrm{in}}\gt 2.2\times {10}^{-1}\,{\text{}}{M}_{\odot }$ ${\mathrm{yr}}^{-1}{(1+Z/{10}^{-2}{\text{}}{Z}_{\odot })}^{-1}({c}_{{\rm{s}}}/10$ $\mathrm{km}\,{{\rm{s}}}^{-1})$ , where cs is the sound speed in the gaseous disk. With increasing numerical resolution, vigorous disk fragmentation reduces the disk surface density, and dynamical heating by formed clumps makes the disk geometrically thicker. As a result, the photoevaporative mass-loss rate rises and thus the critical injection rate increases for fixed metallicity. This process enables super-Eddington growth of BHs until the BH mass reaches ${M}_{\mathrm{BH}}\sim {10}^{7\mbox{--}8}\,{\text{}}{M}_{\odot }$ , depending on the properties of the host dark-matter halo and metal-enrichment history. In the assembly of protogalaxies, seed BHs that form in overdense regions with a mass variance of 3-4σ at z ∼ 15-20 are able to undergo short periods of rapid growth and transit into the Eddington-limited growth phase afterward to be supermassive BHs observed at z &gt; 6-7.

Keywords: Hydrodynamical simulations, Supermassive black holes
Cosmological Parameter Estimation from the Two-dimensional Genus Topology—Measuring the Expansion History Using the Genus Amplitude as a Standard Ruler. We measure the genus of the galaxy distribution in two-dimensional slices of the SDSS-III BOSS catalog to constrain the cosmological parameters governing the expansion history of the universe. The BOSS catalogs are divided into 12 concentric shells over the redshift range 0.25 &lt; z &lt; 0.6, and we repeatedly measure the genus from the two-dimensional galaxy density fields, each time varying the cosmological parameters used to infer the distance-redshift relation to the shells. We also indirectly reconstruct the two-dimensional genus amplitude using the three-dimensional genus measured from SDSS Main Galaxy Sample with galaxies at low redshift z &lt; 0.12. We combine the low- and high-redshift measurements, finding the cosmological model that minimizes the redshift evolution of the genus amplitude, using the fact that this quantity should be conserved. Being a distance measure, the test is sensitive to the matter density parameter (Ωm) and equation of state of dark energy (wde). We find a constraint of ${w}_{\mathrm{de}}=-{1.05}_{-0.12}^{+0.13}$ , Ωm = 0.303 ± 0.036 after combining the high- and low-redshift measurements and combining with Planck CMB data. Higher-redshift data and combining data sets at low redshift will allow for stronger constraints.

Keywords: Cosmology, Cosmological parameters, Large-scale structure of the universe, Observational cosmology, Cosmological parameters from large-scale structure, Dark energy
Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548. In this contribution, we achieve the primary goal of the active galactic nucleus (AGN) STORM campaign by recovering velocity-delay maps for the prominent broad emission lines (Lyα, C IV, He II, and Hβ) in the spectrum of NGC 5548. These are the most detailed velocity-delay maps ever obtained for an AGN, providing unprecedented information on the geometry, ionization structure, and kinematics of the broad-line region. Virial envelopes enclosing the emission-line responses show that the reverberating gas is bound to the black hole. A stratified ionization structure is evident. The He II response inside 5-10 lt-day has a broad single-peaked velocity profile. The Lyα, C IV, and Hβ responses extend from inside 2 to outside 20 lt-day, with double peaks at ±2500 km s-1 in the 10-20 lt-day delay range. An incomplete ellipse in the velocity-delay plane is evident in Hβ. We interpret the maps in terms of a Keplerian disk with a well-defined outer rim at R = 20 lt-day. The far-side response is weaker than that from the near side. The line-center delay $\tau =(R/c)(1-\sin i)\approx 5$ days gives the inclination i ≈ 45°. The inferred black hole mass is MBH ≈ 7 × 107 M⊙. In addition to reverberations, the fit residuals confirm that emission-line fluxes are depressed during the "BLR Holiday" identified in previous work. Moreover, a helical "Barber-Pole" pattern, with stripes moving from red to blue across the C IV and Lyα line profiles, suggests azimuthal structure rotating with a 2 yr period that may represent precession or orbital motion of inner-disk structures casting shadows on the emission-line region farther out.

Keywords: Supermassive black holes, Reverberation mapping, Active galaxies, Active galactic nuclei, Astrophysical black holes
Measuring Black Hole Masses from Tidal Disruption Events and Testing the M<SUB>BH</SUB>-σ<SUB>*</SUB> Relation. Liu and collaborators recently proposed an elliptical accretion disk model for tidal disruption events (TDEs). They showed that the accretion disks of optical/UV TDEs are large and highly eccentric and suggested that the broad optical emission lines with complex and diverse profiles originate in a cool eccentric accretion disk of random inclination and orientation. In this paper, we calculate the radiation efficiency of the elliptical accretion disk and investigate the implications for observations of TDEs. We compile observational data for the peak bolometric luminosity and total radiation energy after peak brightness of 18 TDE sources and compare these data to the predictions from the elliptical accretion disk model. Our results show that the observations are consistent with the theoretical predictions and that the majority of the orbital energy of the stellar debris is advected into the black hole (BH) without being converted into radiation. Furthermore, we derive the masses of the disrupted stars and the masses of the BHs of the TDEs. The BH masses obtained in this paper are also consistent with those calculated with the MBH-σ* relation. Our results provide an effective method for measuring the masses of BHs in large numbers of TDEs to be discovered in ongoing and next-generation sky surveys, regardless of whether the BHs are located at the centers of galactic nuclei or wander in disks and halos.

Keywords: Accretion, Supermassive black holes, Tidal disruption, M-sigma relation
Afterglow Light Curves of Nonrelativistic Ejecta Mass in a Stratified Circumstellar Medium. We present the afterglow light curves produced by the deceleration of a nonrelativistic ejecta mass in a stratified circumstellar medium with a density profile n(r) ∝ r-k with k = 0, 1, 1.5, 2, and 2.5. Once the ejecta mass is launched with equivalent kinetic energy parameterized by E(&gt;β) ∝ β-α (where β is the ejecta velocity) and propagates into the surrounding circumstellar medium, it first moves with constant velocity (the free-coasting phase), and later it decelerates (the Sedov-Taylor expansion). We present the predicted synchrotron and synchrotron self-Compton light curves during the free-coasting phase and the subsequent Sedov-Taylor expansion. In particular cases, we show the corresponding light curves generated by the deceleration of several ejecta masses with different velocities launched during the coalescence of binary compact objects and the core collapse of dying massive stars, which will contribute at distinct timescales, frequencies, and intensities. Finally, using the multiwavelength observations and upper limits collected by a large campaign of orbiting satellites and ground telescopes, we constrain the parameter space of both the kilonova (KN) afterglow in GW170817 and the possibly generated KN afterglow in S190814bv. Further observations on timescales of years post-merger are needed to derive tighter constraints.

Keywords: Gravitational wave astronomy, Gamma-ray bursts, Non-thermal radiation sources, Compact binary stars
The X-Ray Bursts of XTE J1739-285: A NICER Sample. In this work, we report on observations with the Neutron Star Interior Composition Explorer of the known neutron star X-ray transient XTE J1739-285. We observed the source in 2020 February and March, finding it in a highly active bursting state. Across a 20 day period, we detected 32 thermonuclear X-ray bursts, with an average burst recurrence time of ${2.0}_{-0.3}^{+0.4}\,\mathrm{hr}$ . A timing and spectral analysis of the ensemble of X-ray bursts reveals homogeneous burst properties, evidence for short-recurrence time bursts, and the detection of a 386.5 Hz burst oscillation candidate. The latter is especially notable, given that a previous study of this source claimed a 1122 Hz burst oscillation candidate. We did not find any evidence of variability near 1122 Hz and instead find that the 386.5 Hz oscillation is the more prominent signal of the two burst oscillation candidates. Hence, we conclude it is unlikely that XTE J1739-285 has a submillisecond rotation period.

Keywords: Low-mass x-ray binary stars, X-ray bursts
Ring Formation by Coagulation of Dust Aggregates in the Early Phase of Disk Evolution around a Protostar. Ring structures are observed through (sub)millimeter dust continuum emission in various circumstellar disks from the early stages of class 0 and I to the late stage of class II young stellar objects (YSOs). In this paper, we study one of the possible scenarios for such ring formation, which is the coagulation of dust aggregates in the early stage. The dust grains grow in an inside-out manner because the growth timescale is roughly proportional to the orbital period. The boundary of the dust evolution can be regarded as the growth front, where the growth time is comparable to the disk age. Using radiative transfer calculations based on the dust coagulation model, we find that the growth front can be observed as a ring structure because the dust surface density changes sharply at this position. Furthermore, we confirm that the observed ring positions in YSOs with an age of ≲1 Myr are consistent with the growth front. The growth front could be important in creating the ring structure in particular for the early stage of disk evolution, such as class 0 and I sources.

Keywords: Planetary system formation, Young stellar objects, Dust continuum emission, Protoplanetary disks, Interstellar medium, Circumstellar disks, Star formation, Protostars
Formation of Multiple-planet Systems in Resonant Chains around M Dwarfs. Recent observations have revealed the existence of multiple-planet systems composed of Earth-mass planets around late M dwarfs. Most of their orbits are close to commensurabilities, which suggests that planets were commonly trapped in resonant chains in their formation around low-mass stars. We investigate the formation of multiple-planet systems in resonant chains around low-mass stars. A time-evolution model of the multiple-planet formation via pebble accretion in the early phase of the disk evolution is constructed based on the formation model for the TRAPPIST-1 system by Ormel et al. Our simulations show that knowing the protoplanet appearance timescale is important for determining the number of planets and their trapped resonances: as the protoplanet appearance timescale increases, fewer planets are formed, which are trapped in more widely separated resonances. We find that there is a range of the protoplanet appearance timescale for forming stable multiple-planet systems in resonant chains. This range depends on the stellar mass and disk size. We suggest that the protoplanet appearance timescale is a key parameter for studying the formation of multiple-planet systems with planets in resonant chains around low-mass stars. The composition of the planets in our model is also discussed.

Keywords: Planetary system formation, Exoplanet evolution, Exoplanet formation, Planet formation