adsabs/SciX_UAT_keywords huggingface dataset:
The JPL Planetary and Lunar Ephemerides DE440 and DE441

The planetary and lunar ephemerides called DE440 and DE441 have been generated by fitting numerically integrated orbits to ground-based and space-based observations. Compared to the previous general-purpose ephemerides DE430, seven years of new data have been added to compute DE440 and DE441, with improved dynamical models and data calibration. The orbit of Jupiter has improved substantially by fitting to the Juno radio range and Very Long Baseline Array (VLBA) data of the Juno spacecraft. The orbit of Saturn has been improved by radio range and VLBA data of the Cassini spacecraft, with improved estimation of the spacecraft orbit. The orbit of Pluto has been improved from use of stellar occultation data reduced against the Gaia star catalog. The ephemerides DE440 and DE441 are fit to the same data set, but DE441 assumes no damping between the lunar liquid core and the solid mantle, which avoids a divergence when integrated backward in time. Therefore, DE441 is less accurate than DE440 for the current century, but covers a much longer duration of years -13,200 to +17,191, compared to DE440 covering years 1550-2650.

Keywords: celestial mechanics; orbital motion; orbits; solar system planets; solar system; the sun; the moon; earth-moon system; solar system astronomy; pluto
A Numerical Scheme for General Relativistic Radiation Magnetohydrodynamics Based on Solving a Grid-based Boltzmann Equation

We develop a general relativistic radiation magnetohydrodynamics (GR-RMHD) code INAZUMA in which the time-dependent radiation transfer equation (frequency-integrated Boltzmann equation) is solved in curved spacetime. The Eddington tensor is derived from the specific intensity, and we solve the zeroth and first moment equations in order to update the radiation fields. Therefore, our code can solve the radiation field around relativistic compact objects more appropriately than an approximation method like the M1 closure scheme. The numerical scheme of magnetohydrodynamics is the same as that of our previous code. In some test calculations for propagating radiation and radiation hydrodynamics in flat spacetime, our code shows similar results to our previous work. Radiation propagation in curved spacetime is also properly solved for. We also show the radiation transport from the super-Eddington accretion disk around the black hole. The disk structure, such as the density, velocity, and temperature, is fixed by the model obtained using the GR-RMHD simulation with the M1 method. We found that the difference between our scheme and the M1 method appears in the optically thin outflow region around the rotation axis while the radiation field is almost the same in the optically thick disk region.

Keywords: radiative magnetohydrodynamics; general relativity; accretion
The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C 82

3C 82 at a redshift of 2.87 is the most distant 3C (Third Cambridge Catalogue) quasar. Thus, it is a strong candidate to have the most-luminous radio lobes in the universe. 3C 82 belongs to the class of compact steep-spectrum radio sources. We use single-dish and interferometric radio observations in order to model the plasma state of these powerful radio lobes. It is estimated that the long-term time-averaged jet power required to fill these lobes with leptonic plasma is $\overline{Q}\approx 2.66\pm 1.33\times {10}^{47}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ , among the largest time-averaged jet powers from a quasar. Positing protonic lobes is not tenable as they would require two orders of magnitude more mass transport to the lobes than was accreted to the central black hole during their formation. The first high signal-to-noise optical spectroscopic observation obtained of this object indicates that there is a powerful high-ionization broad-line wind with a kinetic power of ∼1045 erg s-1 and a velocity of ∼0.01c. We also estimate from the broad lines in 2018 and the UV continuum in three epochs spread out over three decades that the accretion flow bolometric luminosity is Lbol ≈ 3.2-5.8 × 1046 erg s-1. The ratio of $\bar{Q}/{L}_{{\rm{bol}}}\approx 5.91\pm 3.41$ is perhaps the largest of any known quasar. Extremely powerful jets tend to strongly suppress powerful winds of ionized baryonic matter. Consequently, 3C 82 provides a unique laboratory for studying the dynamical limits of the central engine of outflow initiation in quasars.

Keywords: black hole physics; radio jets; relativistic jets; radio loud quasars
Formation of the Simplest Amide in Molecular Clouds: Formamide (NH2CHO) and Its Derivatives in H2O-rich and CO-rich Interstellar Ice Analogs upon VUV Irradiation

The astronomical detection of formamide (NH2CHO) toward various star-forming regions and in cometary material implies that the simplest amide might have an early origin in dark molecular clouds at low temperatures. Laboratory studies have proven the efficient NH2CHO formation in interstellar CO:NH3 ice analogs upon energetic processing. However, it is still under debate, whether the proposed radical-radical recombination reactions forming complex organic molecules remain valid in an abundant H2O environment. The aim of this work was to investigate the formation of NH2CHO in H2O- and CO-rich ices under conditions prevailing in molecular clouds. Therefore, different ice mixtures composed of H2O:CO:NH3 (10:5:1), CO:NH3 (4:1), and CO:NH3 (0.6:1) were exposed to vacuum ultraviolet photons in an ultra-high vacuum chamber at 10 K. Fourier-transform infrared spectroscopy was utilized to monitor in situ the initial and newly formed species as a function of photon fluence. The infrared spectral identifications are complementarily secured by a temperature-programmed desorption experiment combined with a quadrupole mass spectrometer. The energetic processing of CO:NH3 ice mixtures mainly leads to the formation of NH2CHO, along with its chemical derivatives such as isocyanic acid (HNCO) and cyanate ion (OCN-). The formation kinetics of NH2CHO shows an explicit dependency on ice ratios and compositions; the highest yield is found in H2O-rich ice. The astronomical relevance of the resulting reaction network is discussed.

Keywords: astrochemistry; laboratory astrophysics; dense interstellar clouds; surface processes
Causal Interaction between the Subsurface Rotation Rate Residuals and Radial Magnetic Field in Different Timescales

We studied the presence and spatiotemporal characteristics and evolution of the variations in the differential rotation rates and radial magnetic fields in the Schwabe and quasi-biennial-oscillation (QBO) timescales. To achieve these objectives, we used rotation rate residuals and radial magnetic field data from the Michelson Doppler Imager on the Solar and Heliospheric Observatory and the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory, extending from 1996 May to 2020 August, covering solar cycles 23 and 24, respectively. Under the assumption that the radial surface magnetic field is nonlocal and the differential rotation is symmetric around the equator, our results suggest that the source region of the Schwabe cycle is confined between ~30° N and S throughout the convection zone. As for the source region of the QBO, our results suggest that it is below 0.78 R ⊙.

Keywords: the sun; solar rotation; solar magnetic fields; solar interior
Exploring the Perturbed Milky Way Disk and the Substructures of the Outer Disk

The recent discovery of a spiral feature in the Z - VZ phase plane in the solar neighborhood implies that the galactic disk has been remarkably affected by a dwarf galaxy passing through it some hundreds of millions of years ago. Using 429,500 Large Sky Area Multi-Object Fibre Spectroscopic Telescope K giants stars, we show that the spiral feature exists not only in the solar vicinity but it also extends to about 15 kpc from the Galactic center and then disappears beyond this radius. Moreover, we find that when the spiral features in a plot of Vφ as a function of position in the Z - VZ plane at various galactocentric radii are remapped to the R - Z plane, the spiral can explain well the observed asymmetric velocity substructures. This is evidence that the phase spiral features are the same as the bulk motions found in previous work as well as this work. Test particle simulations and N-body simulations show that an encounter with a dwarf galaxy a few hundred million years ago will induce a perturbation in the galactic disk. In addition, we find that the last impact of Sgr dSph can also contribute to the flare. As a consequence of the encounter, the distribution function of disk stars at a large range of radii is imprinted by the gravitational perturbation.

Keywords: milky way disk
Extreme Tidal Stripping May Explain the Overmassive Black Hole in Leo I: A Proof of Concept

A recent study found dynamical evidence of a supermassive black hole of ~3 × 106 M ⊙ at the center of Leo I, the most distant dwarf spheroidal galaxy of the Milky Way. This black hole, comparable in mass to the Milky Way's Sgr A*, places the system >2 orders of magnitude above the standard M •-M ⋆ relation. We investigate the possibility, from a dynamical standpoint, that Leo I's stellar system was originally much more massive and, thus, closer to the relation. Extreme tidal disruption from one or two close passages within the Milky Way's virial radius could have removed most of its stellar mass. A simple analytical model suggests that the progenitor of Leo I could have experienced a mass loss in the range 32%-57% from a single pericenter passage, depending on the stellar velocity dispersion estimate. This mass-loss percentage increases to the range 66%-78% if the pericenter occurs at the minimum distance allowed by current orbital reconstructions. Detailed N-body simulations show that the mass loss could reach ~90% with up to two passages, again with pericenter distances compatible with the minimum value allowed by Gaia data. Despite very significant uncertainties in the properties of Leo I, we reproduce its current position and velocity dispersion, as well as the final stellar mass enclosed in 1 kpc (~5 × 106 M ⊙) within a factor <2. The most recent tidal stream is directed along our line of sight toward Leo I, making it difficult to detect. Evidence from this extreme tidal disruption event could be present in current Gaia data in the form of extended tidal streams.

Keywords: supermassive black holes; dwarf galaxies; dwarf spheroidal galaxies; milky way dynamics; tidal disruption
Doppler Factor Estimation for Fermi Blazars

In this work, we exploit the luminosity of the broad-line region (BLR) for 50 Fermi blazars through matching the coordinates between the Sloan Digital Sky Survey catalog, Fermi Large Area Telescope Third Source Catalog, and the Fermi Large Area Telescope Fourth Source Catalog and fitting their emission lines. In total, we collected a sample of 350 blazars with broad-line emissions including 50 new objects and 300 blazars from published works to revisit the correlation between the γ-ray luminosity and the broad-line luminosity, and proposed a new method to estimate the Doppler factors based on the correlation between the radiative power of the jet and luminosity of the BLR. We come to following conclusions. (1) For the 50 Fermi blazars, their broad-line luminosity (log LBLR) ranges from 41.82-45.2 erg s-1 with a mean value of 44.39 erg s-1. (2) The Doppler factor (δ) ranges from δ = 0.35 to δ = 85.66 with a mean value of 12.54, which is consistent with the results in the literature. (3) There are positive correlations between γ-ray luminosity and broad-line luminosity, and between γ-ray luminosity and the Doppler factor.

Keywords: jets; high energy astrophysics; active galactic nuclei; blazars
The Global 2:1 Mean-motion Resonance in HD 110067 is Not Vacant!

Extensive modeling of observations obtained by two space telescopes and 14 ground-based observatories revealed the presence of at least six closely packed planets orbiting HD 110067. Their orbital periods form a nearly perfect resonant chain, in which adjacent periods are in a geometric sequence with a ratio of r = 3/2 (planets b to e) that switches to r = 4/3 (planets e to g). The latter part of the sequence is based on single transits of planets f and g and their periods are model-dependent, as only first-order mean-motion resonances (MMRs) were so far investigated; and there is no physical justification for this assumption besides the simplicity imprinted on to the resonant chain itself. Furthermore, the global 2:1 MMR is apparently occupied, whereas this orbit is vacant in all other multibody (extra) solar systems. We summarize the physical arguments for/against the above r = 4/3 period ratios in anticipation of future observations to resolve the issue.

Keywords: exoplanet dynamics; exoplanets; orbital resonances; tidal interaction
FORCASTing the Spectroscopic Dust Properties of the WC+O Binary WR 137 with SOFIA

WR 137 (HD 192641) is a binary system consisting of a carbon-rich Wolf-Rayet (W-R) star and an Oe companion star in a 13 yr orbit. Near periastron, the winds of the two stars collide and form carbonaceous dust. We obtained three mid-infrared grism spectra of the system with SOFIA and FORCAST during the last year of SOFIA's operations in 2021 July, 2021 February, and 2022 May (Cycle 9). Within these spectra, we have identified several wind lines from He I, He II, C III, and C IV that are emitted from the W-R wind as well as a weak emission feature around 6.3-6.4 μm that may have shifted its peak flux from 6.29 to 6.41 μm through this time period. The weak feature grew as the continuum dust emission grew while the W-R emission appeared to decline due to lower contrast with the continuum. Furthermore, we observe that the peak of the feature shifts to redder wavelengths during the observations. We compare this feature to the unidentified infrared feature and other emission lines identified in dusty carbon-rich W-R (WC) binaries. For WR 137, we speculate that mixing of the winds in the system with the Oe star's disk is important for starting the dust formation and that it is less important as dust formation continues. Previous infrared photometry shows "minieruptions" of dust production, which could then be explained with variations of the Oe star disk.

Keywords: wolf-rayet stars; early-type stars; oe stars; dust formation; binary stars; stellar winds
Finding of a Population of Active Galactic Nuclei Showing a Significant Luminosity Decline in the Past 103-104 yr

Recent observations have revealed an interesting active galactic nucleus (AGN) subclass that shows strong activity at large scales (~1 kpc) but weaker at small scales (<10 pc), suggesting a strong change in the mass accretion rate of the central engine in the past 103-104 yr. We systematically search for such declining or fading AGNs by cross-matching the Sloan Digital Sky Survey type 1 AGN catalog at z < 0.4, covering the [O III] λ5007 emission line, which is a tracer for the narrow-line region emission, with the Wide-field Infrared Survey Explorer (WISE) mid-infrared (MIR) catalog covering the emissions from the dusty tori. Out of the 7653 sources, we found 57 AGNs whose bolometric luminosities estimated from the MIR band are at least one order of magnitude fainter than those estimated from the [O III] λ5007 emission line. This luminosity-declining AGN candidate population shows four important properties: (1) the past AGN activity estimated from the [O III] λ5007 line reaches approximately the Eddington limit; (2) more than 30% of the luminosity-declining AGN candidates show a large absolute variability of ΔW1 > 0.45 mag in the previous ~10 yr at the WISE 3.4 μm band; (3) the median ratio of log([N II] λ6584/Hα λ6563) = -0.52, suggesting a lower gas metallicity and/or higher ionization parameter compared to other AGN populations; and (4) the second-epoch spectra of the population indicate a spectral type change for 15% of the sources. This population provides insights on the possible connection between the luminosity decline that started ~103-104 yr ago and the decline in the recent 10 yr.

Keywords: active galactic nuclei; quasars; galaxies
The Influence of Cold Jupiters in the Formation of Close-in Planets. I. Planetesimal Transport

The formation of a cold Jupiter (CJ) is expected to quench the influx of pebbles and the migration of cores interior to its orbit, thus limiting the efficiency of rocky planet formation either by pebble accretion and/or orbital migration. Observations, however, show that the presence of outer CJs (>1 au and ≳0.3M Jup) correlates with the presence of inner super-Earths (at <1 au). This observation may simply be a result of an enhanced initial reservoir of solids in the nebula required to form a CJ or a yet-to-be-determined mechanism assisted by the presence of the CJ. In this work, we focus on the latter alternative and study the orbital transport of planetesimals interior to a slightly eccentric (~0.05) CJ subject to the gravity and drag from a viscously evolving gaseous disk. We find that a secular resonance sweeping inward through the disk gradually transports rings of planetesimals when their drag-assisted orbital decay is faster than the speed of the resonance scanning. This snowplow-like process leads to large concentration (boosted by a factor of ~10-100) of size-segregated planetesimal rings with aligned apsidal lines, making their expected collisions less destructive, due to their reduced velocity dispersion. This process is efficient for a wide range of α-disk models (and thus disk lifetimes) and Jovian masses, peaking for values ~1-5M Jup, which are typical of observed CJs in radial velocity surveys. Overall, our work highlights the major role that the disk's gravity may have on the orbital redistribution of planetesimals, depicting a novel avenue by which CJs may enhance the formation of inner planetary systems, including super-Earths and perhaps even warm and hot Jupiters.

Keywords: exoplanet formation; planet formation; protoplanetary disks; planetary-disk interactions
Mass Accretion Rates of the HectoMAP Clusters of Galaxies

We estimate the mass accretion rate (MAR) of 321 clusters of galaxies in the HectoMAP Cluster Survey. The clusters span the redshift range 0.17-0.42 and the M 200 mass range ≈ (0.5-3.5) × 1014 M ⊙. The MAR estimate is based on the caustic technique along with a spherical infall model. Our analysis extends the measurement of MARs for 129 clusters at z < 0.3 from the Cluster Infall Regions in the Sloan Digital Sky Survey and the Hectospec Cluster Survey to redshift z ~ 0.42. Averaging over redshift, low-mass clusters with masses near 0.7 × 1014 M ⊙ roughly accrete 3 × 104 M ⊙ yr-1; more massive clusters with masses near 2.8 × 1014 M ⊙ roughly accrete 1 × 105 M ⊙ yr-1. Low- and high-mass clusters increase their MAR by approximately 46% and 84%, respectively, as the redshift increases from z in the range 0.17-0.29 to z in the range 0.34-0.42. The MARs at fixed redshift increase with mass and MARs at fixed mass increase with redshift in agreement with the ΛCDM cosmological model for hierarchical structure formation. We consider the extension of MAR measurements to z ~ 1.

Keywords: galaxy clusters; galaxy dynamics; galaxy kinematics; observational cosmology; cosmology; hierarchical cosmology; large-scale structure of the universe; dark matter distribution
Thermal Damping of Weak Magnetosonic Turbulence in the Interstellar Medium

We present a generic mechanism for the thermal damping of compressive waves in the interstellar medium (ISM), occurring due to radiative cooling. We solve for the dispersion relation of magnetosonic waves in a two-fluid (ion-neutral) system in which density- and temperature-dependent heating and cooling mechanisms are present. We use this dispersion relation, in addition to an analytic approximation for the nonlinear turbulent cascade, to model dissipation of weak magnetosonic turbulence. We show that in some ISM conditions, the cutoff wavelength for magnetosonic turbulence becomes tens to hundreds of times larger when the thermal damping is added to the regular ion-neutral damping. We also run numerical simulations, which confirm that this effect has a dramatic impact on cascade of compressive wave modes.

Keywords: interstellar medium; interstellar dynamics; interstellar phases; interstellar atomic gas
The Importance of the Upper Atmosphere to CO/O2 Runaway on Habitable Planets Orbiting Low-mass Stars

Efforts to spectrally characterize the atmospheric compositions of temperate terrestrial exoplanets orbiting M dwarf stars with JWST are now underway. Key molecular targets of such searches include O2 and CO, which are potential indicators of life. Recently, it was proposed that CO2 photolysis generates abundant (≳0.1 bar) abiotic O2 and CO in the atmospheres of habitable M dwarf planets with CO2-rich atmospheres, constituting a strong false positive for O2 as a biosignature and further complicating efforts to use CO as a diagnostic of surface biology. Importantly, this implied that TRAPPIST-1e and TRAPPIST-1f, now under observation with JWST, would abiotically accumulate abundant O2 and CO, if habitable. Here, we use a multi-model approach to reexamine photochemical O2 and CO accumulation on planets orbiting M dwarf stars. We show that photochemical O2 remains a trace gas on habitable CO2-rich M dwarf planets, with earlier predictions of abundant O2 and CO due to an atmospheric model top that was too low to accurately resolve the unusually high CO2 photolysis peak on such worlds. Our work strengthens the case for O2 as a biosignature gas, and affirms the importance of CO as a diagnostic of photochemical O2 production. However, observationally relevant false-positive potential remains, especially for O2's photochemical product O3, and further work is required to confidently understand O2 and O3 as biosignature gases on M dwarf planets.

Keywords: extrasolar rocky planets; m dwarf stars; biosignatures; exoplanet atmospheric composition; habitable planets; theoretical models
Selenographic and Local Time Dependence of Lunar Exospheric Sodium as Observed by LADEE

Even though sodium (Na) has been known to be a constituent of the lunar exosphere for the past thirty years, limitations introduced by Earth-based observations make it difficult to determine how its distribution varies with local time. We used observations from the Ultraviolet and Visible Spectrometer instrument on board the NASA Lunar Atmosphere and Dust Environment Explorer mission to search for evidence of near-instantaneous dayside variation of exospheric Na across one lunation (2014 February-March). Through comparison with model simulations, the data appear to be consistent with persistent southern enhancements of Na, while no evidence of systematic depletion of the Na exosphere reservoir within two hours of local noon was obtained. The results indicate an enhancement of the gas density over Mare regions and the lunar nearside; though this finding could mean that the weak Na emission is lost in the scattering continuum over brighter soils. Day-to-day variability is observed and may reflect a changing solar wind and meteoroid environment combined with inhomogeneities in the gas-surface interaction parameters and Na distribution on the lunar surface. We found that, due to the limited viewing geometry and sensitivity of the instrument to scattering from the bright lunar surface, it is difficult to uniquely separate the latitudinal and local time variations of Na.

Keywords: lunar composition; lunar atmosphere; exosphere