Sazuna/UAT_keywords huggingface dataset:
Pulsar Timing Array Constraints on the Merger Timescale of Subparsec Supermassive Black Hole Binary Candidates. We estimate the merger timescale of spectroscopically selected, subparsec supermassive black hole binary (SMBHB) candidates by comparing their expected contribution to the gravitational-wave background (GWB) with the sensitivity of current pulsar timing array (PTA) experiments and in particular, with the latest upper limit placed by the North American Nanohertz Observatory for Gravitational Waves. We find that the average timescale to coalescence of such SMBHBs is $\langle {t}_{\mathrm{evol}}\rangle \gt 6\times {10}^{4}\,$ yr, assuming that their orbital evolution in the PTA frequency band is driven by emission of gravitational waves. If some fraction of SMBHBs do not reside in spectroscopically detected active galaxies, and their incidence in active and inactive galaxies is similar, then the merger timescale could be ∼10 times longer, $\langle {t}_{\mathrm{evol}}\rangle \gt 6\times {10}^{5}\,$ yr. These limits are consistent with the range of timescales predicted by theoretical models and imply that all the SMBHB candidates in our spectroscopic sample could be binaries without violating the observational constraints on the GWB. This result illustrates the power of the multimessenger approach, facilitated by the PTAs, in providing an independent statistical test of the nature of SMBHB candidates discovered in electromagnetic searches.

Keywords: Supermassive black holes, Gravitational waves, Active galactic nuclei, Galaxy mergers
Geometry of the Draco C1 Symbiotic Binary. Draco C1 is a known symbiotic binary star system composed of a carbon red giant and a hot, compact companion—likely a white dwarf—belonging to the Draco dwarf spheroidal galaxy. From near-infrared spectroscopic observations taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), part of Sloan Digital Sky Survey IV, we provide updated stellar parameters for the cool, giant component, and constrain the temperature and mass of the hot, compact companion. Prior measurements of the periodicity of the system, based on only a few epochs of radial velocity data or relatively short baseline photometric observations, were sufficient only to place lower limits on the orbital period (P &gt; 300 days). For the first time, we report precise orbital parameters for the binary system: with 43 radial velocity measurements from APOGEE spanning an observational baseline of more than 3 yr, we definitively derive the period of the system to be ${1220.0}_{-3.5}^{+3.7}$ days. Based on the newly derived orbital period and separation of the system, together with estimates of the radius of the red giant star, we find that the hot companion must be accreting matter from the dense wind of its evolved companion.

Keywords: Draco dwarf galaxy, Binary stars, White dwarf stars, Carbon stars, Spectroscopy, Radial velocity, Symbiotic binary stars
An Independent Analysis of the Six Recently Claimed Exomoon Candidates. It has been recently claimed that KOIs-268.01, 303.01, 1888.01, 1925.01, 2728.01, and 3320.01 are exomoon candidates, based on an analysis of their transit timing. Here, we perform an independent investigation, which is framed in terms of three questions: (1) Are there significant transit timing variations (TTVs)? (2) Is there a significant periodic TTV? (3) Is there evidence for a nonzero moon mass? We applied rigorous statistical methods to these questions alongside a reanalysis of the Kepler photometry and find that none of the Kepler objects of interest (KOIs) satisfy our three tests. Specifically, KOIs-268.01 and 3220.01 pass none of the tests and KOIs-303.01, 1888.01, and 1925.01 pass a single test each. Only KOI-2728.01 satisfies two, but fails the cross-validation test for predictions. Further, detailed photodynamical modeling reveals that KOI-2728.01 favors a negative-radius moon (as does KOI-268.01). We also note that we find a significant photoeccentric effect for KOI-1925.01 indicating an eccentric orbit of at least e &gt; (0.62 ± 0.06). For comparison, we applied the same tests to Kepler-1625b, which reveals that (1) and (3) are passed, but (2) cannot be checked with the cross-validation method used here, due to the limited number of available epochs. In conclusion, we find no compelling evidence for exomoons among the six KOIs. Despite this, we were able to derive exomoon mass upper limits versus semimajor axis, with KOI-3220.01 leading to particularly impressive constraints of MS/MP &lt; 0.4% [2σ] at a similar semimajor to that of the Earth-Moon.

Keywords: Exoplanet dynamics, Natural satellites (Extrasolar), Exoplanets
Characterization of Temporarily Captured Minimoon 2020 CD<SUB>3</SUB> by Keck Time-resolved Spectrophotometry. We present time-resolved visible spectrophotometry of 2020 CD3, the second known minimoon. The spectrophotometry was taken with the Keck I/Low Resolution Imaging Spectrometer between wavelengths 434 and 912 nm in the B, g, V, R, I, and RG850 filters as it was leaving the Earth-Moon system on 2020 March 23 UTC. The spectrum of 2020 CD3 resembles V-type asteroids and some lunar rock samples with a 434-761 nm reddish slope of ∼18%/100 nm (g-r = 0.62 ± 0.08 and r-i = 0.21 ± 0.06) with an absorption band at ∼900 nm corresponding to i-z = -0.54 ± 0.10. Combining our measured H of 31.9 ± 0.1 with an albedo of 0.35 typical for V-type asteroids, we determine 2020 CD3's diameter to be ∼0.9 ± 0.1 m, making it the first minimoon and one of the smallest asteroids to be spectrally studied. We use our time-series photometry to detect significant periodic light-curve variations with a period of ∼573 s and amplitude of ∼1. In addition, we extend the observational arc of 2020 CD3 to 37 days, to 2020 March 23 UTC. From the improved orbital solution for 2020 CD3, we estimate the likely duration of its capture to be ∼2 yr and the nongravitational perturbation on its orbit due to radiation pressure with an area-to-mass ratio of (6.9 ± 2.4) × 10-4 m2 kg-1 implying a density of 2.3 ± 0.8 g cm-3, broadly compatible with other meter-scale asteroids and lunar rock. We searched for prediscovery detections of 2020 CD3 in the Zwicky Transient Facility archive as far back as 2018 October but were unable to locate any positive detections.

Keywords: Near-Earth objects, Asteroids, Meteoroids
An X-Ray Luminosity-dependent "Changing-look" Phenomenon in UGC 3223. The nature of the rare "Changing-look" (CL) phenomenon in active galactic nuclei (AGNs) is still under debate. We present Swift/XRT and UVOT follow-up observations of UGC 3223, a newly discovered repeat CL-AGN with type transitions of S1.5 → S2 → S1.8 occurring in a period of about 30 yr. By comparing the values previously reported in the ROSAT All-sky Survey and in the second Swift-XRT Point Source catalog, we clearly find that the X-ray flux tightly follows the optical spectral transition, in which a spectral type closer to a Seyfert 1 type is associated with a higher X-ray flux. An invariable X-ray spectral shape is, however, found in the CL phenomenon of the object. An extremely low Eddington ratio of ∼2 × 10-4 can be obtained from the X-ray luminosity for its Seyfert 2 state, which suggests the disk-wind broad-line region model best explains the CL phenomenon. A variation of the total UV emission is not revealed when compared to the previous Galaxy Evolution Explorer NUV observation, since the UVOT images indicate that ∼90% UV emission comes from intensive star formation in the host galaxy.

Keywords: Seyfert galaxies, X-ray active galactic nuclei, Active galactic nuclei
Millimeter-VLBI Detection and Imaging of the Gravitationally Lensed γ-Ray Blazar JVAS B0218+357. We observed the gravitationally lensed blazar JVAS B0218+357 with the KVN and VERA Array (KaVA) at 22, 43, and 86 GHz. The source has recently been identified as an active γ-ray source up to GeV/TeV energy bands, rendering a unique target for studying relativistic jets through gravitational lensing. Here we report the first robust very long baseline interferometry (VLBI) detection and imaging of the lensed images up to 86 GHz. The detected milliarcsecond-scale/parsec-scale morphology of the individual lensed images (A and B) is consistent with that previously seen at 22 and 15 GHz, showing the core-jet morphology with the jet direction being the same as at the low frequencies. The radio spectral energy distributions of the lensed images become steeper at higher frequencies, indicating that the innermost jet regions become optically thin to synchrotron emission. Our findings confirm that the absorption effects due to the intervening lensing galaxy become negligible at millimeter wavelengths. These results indicate that high-frequency VLBI observations are a powerful tool to better recover the intrinsic properties of lensed active galactic nucleus jets, which therefore allow us to study the interplay between the low- and high-energy emission.

Keywords: Very long baseline interferometry, Relativistic jets, Active galactic nuclei
Blazar Radio and Optical Survey (BROS): A Catalog of Blazar Candidates Showing Flat Radio Spectrum and Their Optical Identification in Pan-STARRS1 Surveys. Utilizing the latest and the most sensitive radio and optical catalogs, we completed a new blazar candidate catalog, Blazar Radio and Optical Survey (BROS), which includes 88,211 sources located at decl. δ &gt; -40° and outside the galactic plane ( $| b| \gt 10^\circ $ ). We list compact flat-spectrum radio sources of α &gt; -0.6 (α is defined as Fν ∝ να) from 0.15 GHz TGSS to 1.4 GHz NVSS catalogs. We further identify optical counterparts of the selected sources by cross-matching with Pan-STARRS1 photometric data. Color-color and color-magnitude plots for the selected BROS sources clearly show two distinct populations, a "quasar-like" population consisting of both flat-spectrum radio quasars and BL Lac type objects. On the other hand, an "elliptical-like" population of mostly BL Lac type objects is buried in the elliptical galaxy. The latter population is also reported in previous catalogs, but the BROS catalog provided a new larger sample of this population, due to the lower radio flux threshold of our selection. Model calculations show that the "elliptical-like" population consists of elliptical galaxies located at redshift z ≲ 0.5, which is also supported by the logN-logS distribution of the power-law index of 1.49 ± 0.05. This BROS catalog is useful for identifying the electromagnetic counterparts of ultra-high-energy cosmic rays and PeV neutrinos recently detected by IceCube, as well as nearby BL Lac objects detectable by future high-sensitivity TeV telescopes, such as the Cherenkov Telescope Array.

Keywords: Radio active galactic nuclei, Blazars, Catalogs
Constraining Galactic Structure with the LISA White Dwarf Foreground. White dwarfs (WDs) comprise 95% of all stellar remnants, and are thus an excellent tracer of old stellar populations in the Milky Way. Current and planned telescopes are not able to directly probe the WD population in its entirety due to its inherently low luminosity. However, the Galactic population of double white dwarf binaries (DWDs) gives rise to a millihertz gravitational-wave foreground detectable by the Laser Interferometer Space Antenna (LISA). Here we show how characterizing the angular power of the WD foreground will enable probes of the Galactic structure in a novel way to determine whether the Galactic WD population traces the spatial distribution of young, bright stars, or traces a vertically heated spatial distribution associated with the Galaxy's oldest stellar populations. We do this using a binary population synthesis study that incorporates different Galactic spatial distributions for the DWD population. We find that the level of anisotropy in the WD foreground's angular power spectrum is dependent on the vertical scale height of the population, but show that multipole coefficients from the spherical harmonic decomposition must be considered individually because of LISA's angular resolution. Finally, we show that LISA can probe the vertical scale height of the Galactic WD population with an accuracy of 300 pc, using the hexadecapole moment of the WD foreground.

Keywords: Stellar populations, White dwarf stars, Galaxy dynamics, Galaxy disks, Gravitational wave astronomy
The Mira-Titan Universe. III. Emulation of the Halo Mass Function. We construct an emulator for the halo mass function over group and cluster mass scales for a range of cosmologies, including the effects of dynamical dark energy and massive neutrinos. The emulator is based on the recently completed Mira-Titan Universe suite of cosmological N-body simulations. The main set of simulations spans 111 cosmological models with 2.1 Gpc boxes. We extract halo catalogs in the redshift range z = [0.0, 2.0] and for masses ${M}_{200{\rm{c}}}\geqslant {10}^{13}{M}_{\odot }/h$ . The emulator covers an eight-dimensional hypercube spanned by { ${{\rm{\Omega }}}_{{\rm{m}}}{h}^{2}$ , ${{\rm{\Omega }}}_{{\rm{b}}}{h}^{2}$ , ${{\rm{\Omega }}}_{\nu }{h}^{2}$ , σ8, h, ns, w0, wa}; spatial flatness is assumed. We obtain smooth halo mass functions by fitting piecewise second-order polynomials to the halo catalogs and employ Gaussian process regression to construct the emulator while keeping track of the statistical noise in the input halo catalogs and uncertainties in the regression process. For redshifts z ≲ 1, the typical emulator precision is better than 2% for ${10}^{13}\mbox{--}{10}^{14}{M}_{\odot }/h$ and &lt;10% for $M\simeq {10}^{15}{M}_{\odot }/h$ . For comparison, fitting functions using the traditional universal form for the halo mass function can be biased at up to 30% at $M\simeq {10}^{14}{M}_{\odot }/h$ for z = 0. Our emulator is publicly available at https://github.com/SebastianBocquet/MiraTitanHMFemulator.

Keywords: Large-scale structure of the universe
Rotational Disruption of Dust and Ice by Radiative Torques in Protoplanetary Disks and the Implications for Observations. Dust and ice mantles on dust grains play an important role in various processes in protoplanetary disks (PPDs) around a young star, including planetesimal formation, surface chemistry, and being the reservoir of water in habitable zones. In this paper, we perform two-dimensional modeling of rotational disruption of dust grains and ice mantles due to centrifugal force within suprathermally rotating grains spun-up by radiative torques for disks around T-Tauri and Herbig Ae/Be stars. We first study rotational disruption of large composite grains and find that large aggregates could be disrupted into individual nanoparticles via the RAdiative Torque Disruption (RATD) mechanism. We then study rotational desorption of ice mantles and ro-thermal desorption of molecules from the ice mantle. We find that ice mantles in the disk's warm surface layer and above can be disrupted into small icy fragments, followed by rapid evaporation of molecules. We suggest that the rotational disruption mechanism can replenish the ubiquitous presence of polycyclic aromatic hydrocarbons/nanoparticles in the hot surface layers of PPDs as observed in mid-IR emission, which are presumably destroyed by extreme ultraviolet (UV) stellar photons. We find that the water snowline is more extended in the presence of rotational desorption, which would decrease the number of comets but increase the number of asteroids formed in the solar nebula. Finally, we suggest that RATD breaking up carbonaceous grains more efficiently than it does silicates might resolve the carbon deficit problem measured on the Earth and rocky bodies.

Keywords: Interstellar dust, Astronomy web services, Ice destruction, Interstellar molecules, Protoplanetary disks, Circumstellar dust
Infrared Emission from Cold Gas Dusty Disks in Massive Ellipticals. What is the expected infrared output of elliptical galaxies? We report the latest findings obtained in this high time resolution (∼10 yr) and high spatial resolution (2.5 pc at center) study. We add a set of grain physics to the Massive active galactic nucleus (AGN) Controlled Ellipticals Resolved code, including (a) dust grains made in passive stellar evolution; (b) dust grain growth due to collision and sticking; (c) grain destruction due to thermal sputtering; (d) dust cooling of hot gas via inelastic collisions; and (e) radiation pressure on dust grains. The code improvements enable us to analyze metal depletion and AGN obscuration due to dust, and to assess its infrared output. We simulate a representative massive elliptical galaxy of a central stellar velocity dispersion ∼260 km s-1 and modest rotation. We find that: (1) the circumnuclear disk (∼1 kpc in diameter) is dusty in its outer region where most of the metals are contained in dust grains, while in the inner disk, dust grains are mostly destroyed by the AGN irradiation; (2) the dusty disk is optically thick to both the starlight within the disk and the radiation from the central AGN; thus the AGN is obscured behind the disk, and the covering factor is ∼0.2; and (3) the duty cycles of the AGN activities, star formation, and the dust infrared luminosity roughly match observations; e.g., in most of its lifetime, the simulated galaxy is a stereotypical "quiescent" elliptical galaxy with ${L}_{\mathrm{IR}}\sim {10}^{11}{L}_{\odot }$ , but it can reach ≳1046 erg s-1 during outbursts with a star formation rate $\gtrsim 250\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ .

Keywords: Interstellar dust, Black hole physics, Metallicity, E+A galaxies, Dust continuum emission, Galaxy evolution, Interstellar medium, Elliptical galaxies
Galactic Cosmic-Ray Hydrogen Spectra in the 40-250 MeV Range Measured by the High-energy Particle Detector (HEPD) on board the CSES-01 Satellite between 2018 and 2020. The High-energy Particle Detector (HEPD) on board the China Seismo-Electromagnetic Satellite (CSES-01)—launched on 2018 February 2—is a light and compact payload suitable for measuring electrons (3-100 MeV), protons (30-250 MeV), and light nuclei (up to a few hundreds of MeV). The Sun-synchronous orbit and large acceptance allow HEPD to measure cosmic-ray particles near the ±65° latitude limit for a fair amount of time per day. In this work, three semiannual galactic hydrogen energy spectra between ∼40 and 250 MeV are presented, including a comparison with theoretical spectra from HelMod, a 2D Monte Carlo model developed to simulate the solar modulation of cosmic rays throughout the heliosphere. To our knowledge, these are the first hydrogen energy spectra below 250 MeV measured at 1 au between 2018 and 2020.

Keywords: Cosmic ray detectors, Heliosphere, Cosmic rays
Variability in Protoplanetary Nebulae: VII. Light-curve Studies of Five Medium-bright, Oxygen-rich, or Mixed-chemistry Post-AGB/Post-RGB Objects. We have monitored over a 10-year interval the light variations of five evolved stars with very large mid-infrared excesses. All five objects appear to have oxygen-rich or mixed oxygen-rich and carbon-rich chemistries. They all vary in light: four over a small range of ∼0.2 mag and the fifth over a larger range of ∼0.7 mag. Spectral types range from G2 to B0. Periodic pulsations are found for the first time in the three cooler ones, IRAS 18075-0924 (123 days), 19207+2023 (96 days), and 20136+1309 (142 days). No significant periodicity is found in the hotter ones, but they appear to vary on a shorter timescale of a few days or less. Two also show some evidence of longer-term periodic variations (∼4 yr). Three appear to be protoplanetary nebulae (PPNe), in the post-asymptotic giant branch (post-AGB) phase of stellar evolution. Their light variations are in general agreement with the relationships among temperature, pulsation period, and pulsation amplitude found in previously studied PPNe. The other two, however, appear to have too low a luminosity (1000-1500 L⊙), based on Gaia distances, to be in the post-AGB phase. Instead, they appear to be Milky Way analogs of the recently identified class of dusty post-red giant branch (post-RGB) stars found in the Magellanic Clouds, which likely had their evolution interrupted by interaction with a binary companion. If this is the case, then these would be among the first dusty post-RGB objects identified in the the Milky Way.

Keywords: Post-asymptotic giant branch stars, Pulsating variable stars, Protoplanetary nebulae, Stellar pulsations, Multi-periodic pulsation, Circumstellar matter, Circumstellar dust
Where Are the Extrasolar Mercuries?. We utilize observations of 16 white dwarf stars to calculate and analyze the oxidation states of the parent bodies accreting onto stars. Oxygen fugacity, which is a measure of overall oxidation state for rocks, is as important as pressure and temperature in determining the structure of a planet. We find that most of the extrasolar rocky bodies formed under oxidizing conditions, but that ∼1/4 of the polluted white dwarfs have compositions that are consistent with more reduced parent bodies. The difficulty in constraining the oxidation states of relatively reduced bodies is discussed and a model for the time-dependent evolution of the apparent oxygen fugacity for a hypothetical reduced body engulfed by a WD is investigated. The differences in diffusive fluxes of various elements through the WD envelope yield spurious inferred bulk elemental compositions and oxidation states of the accreting parent bodies under certain conditions. The worst case for biasing against detection of reduced bodies occurs for high effective temperatures. For moderate and low effective temperatures, the evidence for relatively reduced parent bodies is preserved under most circumstances for at least several characteristic lifetimes of the debris disk.

Keywords: Extrasolar rocky planets, White dwarf stars, Exoplanets
Anisotropy of Velocity Centroids and the Signature of Different MHD Modes in the Turbulent ISM. Magnetic turbulence is anisotropic because the directions of motion are constrained by the magnetic field. Such anisotropy can be observed in velocity centroids obtained from spectroscopic observations. We use magnetohydrodynamics (MHD) simulations to produce synthetic spectroscopic observations (position-position-velocity data) and study the anisotropy in the structure function of velocity centroid maps. We decomposed the velocity in the simulations into Alfvén, slow, and fast modes and studied how each of them contributes to the observed anisotropy. We found that when the angle between the line of sight and the mean magnetic field is large the Alfvén mode dominates the observed anisotropy, while for smaller angles the anisotropy is not large enough to be used to probe the magnetization of the medium, and it is dominated by the slow mode. Our results are in fair agreement with the theoretical predictions in Kandel et al.

Keywords: Interstellar magnetic fields, Magnetohydrodynamics, Interstellar clouds, Interstellar medium