adsabs/SciX_UAT_keywords huggingface dataset:
Secular Spin-Orbit Resonances of Black Hole Binaries in AGN Disks

The spin-orbit misalignment of stellar-mass black hole (sBH) binaries provides important constraints on the formation channels of merging sBHs. Here, we study the role of secular spin-orbit resonance in the evolution of an sBH binary component around a supermassive BH (SMBH) in an AGN disk. We consider the sBH's spin precession due to the J 2 moment introduced by a circum-sBH disk within the warping/breaking radius of the disk. We find that the sBH's spin-orbit misalignment (obliquity) can be excited via spin-orbit resonance between the sBH binary's orbital nodal precession and the sBH spin precession driven by a massive circum-sBH disk. Using an α-disk model with Bondi-Hoyle-Lyttleton accretion, the resonances typically occur for sBH binaries with semimajor axis of 1 au and at a distance of ~1000 au around a 107 M ⊙ SMBH. The spin-orbit resonances can lead to high sBH obliquities and a broad distribution of sBH binary spin-spin misalignments. However, we note that the Bondi-Hoyle-Lyttleton accretion is much higher than that of Eddington accretion, which typically results in spin precession being too low to trigger spin-orbit resonances. Thus, secular spin-orbit resonances can be quite rare for sBHs in AGN disks.

Keywords: black hole spin-flip; dynamical evolution; gravitational wave sources; orbits
101 Trojans: A Tale of Period Bimodality, Binaries, and Extremely Slow Rotators from K2 Photometry

Various properties of Jovian Trojan asteroids such as composition, rotation periods, and photometric amplitudes, or the rate of binarity in the population, can provide information and constraints on the evolution of the group and of the solar system itself. Here we present new photometric properties of 45 Jovian Trojans from the K2 mission of the Kepler space telescope, and present phase-folded light curves for 44 targets, including (11351) Leucus, one of the targets of the Lucy mission. We extend our sample to 101 asteroids with previous K2 Trojan measurements, then compare their combined amplitude and frequency distributions to other ground-based and space data. We show that there is a dichotomy in the periods of Trojans with a separation at ∼100 hr. We find that 25% of the sample are slow rotators (P ≥ 30 hr), an excess that can be attributed to binary objects. We also show that 32 systems can be classified as potential detached binary systems. Finally, we calculate density and rotation constraints for the asteroids. Both the spin barrier and fits to strengthless ellipsoid models indicate low densities and thus compositions similar to populations of comets and trans-Neptunian objects throughout the sample. This supports the scenario of outer solar system origin for Jovian Trojans.

Keywords: photometry; trojan asteroids; jupiter trojans
Peculiar Black Hole Accretion Rates in AGN with Highest Star Formation Rates in the Universe

Pouliasis et al. explored star formation rates, black hole accretion rates, and stellar mass of active galaxies at redshift above 3.5, uncovering a leveling off of the star formation rate at high stellar mass, which they consider to be evidence of AGN feedback. Their data shows that as AGN approach the flattening of the curve in the star formation rate-stellar mass plane, the accretion rates begin to drop. We describe the nature of the AGN feedback responsible for this in terms of powerful FRII jets enhancing star formation rates but eventually also triggering a shift in accretion from near-Eddington rates to advection dominated. These systems are on the cusp of a dramatic transition where the active galaxy goes from strong enhancement to large suppression of star formation in a way that produces the steeper slope for radio AGN at low redshift compared to radio AGN at higher redshift and to jetless AGN. We argue, therefore, that the data of Pouliasis et al. constitute the high redshift objects predicted by Singh et al. that connect to the low redshift behavior of radio AGN shown in Comerford et al.

Keywords: quasars; radio loud quasars; radio quiet quasars
Collision Chains among the Terrestrial Planets. III. Formation of the Moon

In the canonical model of Moon formation, a Mars-sized protoplanet "Theia" collides with proto-Earth at close to their mutual escape velocity vesc and a common impact angle ~45°. The "graze-and-merge" collision strands a fraction of Theia's mantle into orbit, while Earth accretes most of Theia and its momentum. Simulations show that this produces a hot, high angular momentum, silicate-dominated protolunar system, in substantial agreement with lunar geology, geochemistry, and dynamics. However, a Moon that derives mostly from Theia's mantle, as angular momentum dictates, is challenged by the fact that O, Ti, Cr, radiogenic W, and other elements are indistinguishable in Earth and lunar rocks. Moreover, the model requires an improbably low initial velocity. Here we develop a scenario for Moon formation that begins with a somewhat faster collision, when proto-Theia impacts proto-Earth at ~ 1.2vesc, also around ~45°. Instead of merging, the bodies come into violent contact for a half hour and their major components escape, a "hit-and-run" collision. N-body evolutions show that the "runner" often returns ~0.1-1 Myr later for a second giant impact, closer to vesc; this produces a postimpact disk of ~2-3 lunar masses in smoothed particle hydrodynamics simulations, with angular momentum comparable to canonical scenarios. The disk ends up substantially inclined, in most cases, because the terminal collision is randomly oriented to the first. Moreover, proto-Earth contributions to the protolunar disk are enhanced by the compounded mixing and greater energy of a collision chain.

Keywords: earth-moon system; planet formation; lunar origin
A Time-efficient, Data-driven Modeling Approach for Predicting the Geomagnetic Impact of Coronal Mass Ejections

To understand the global-scale physical processes behind coronal mass ejection (CME)-driven geomagnetic storms and predict their intensity as a space weather forecasting measure, we develop an interplanetary CME flux rope-magnetosphere interaction module using 3D magnetohydrodynamics. The simulations adequately describe CME-forced dynamics of the magnetosphere including the imposed magnetotail torsion. These interactions also result in induced currents, which are used to calculate the geomagnetic perturbation. Through a suitable calibration, we estimate a proxy of geoeffectiveness-the Storm Intensity index (STORMI)-that compares well with the Dst/SYM-H index. Simulated impacts of two contrasting CMEs quantified by the STORMI index exhibit a high linear correlation with the corresponding Dst and SYM-H indices. Our approach is relatively simple, has fewer parameters to be fine-tuned, and is time efficient compared to complex fluid-kinetic methods. Furthermore, we demonstrate that flux rope erosion does not significantly affect our results. Thus our method has the potential to significantly extend the time window for predictability-an outstanding challenge in geospace environment forecasting-if early predictions of near-Earth CME flux rope structures based on near-Sun observations are available as inputs. This study paves the way for early warnings based on operational predictions of CME-driven geomagnetic storms.

Keywords: solar coronal mass ejections; magnetic storms; space weather
Effect of Equation of State and Cutoff Density in Smoothed Particle Hydrodynamics Simulations of the Moon-forming Giant Impact

The amount of vapor in the impact-generated protolunar disk carries implications for the dynamics, devolatilization, and moderately volatile element isotope fractionation during lunar formation. The equation of state (EoS) used in simulations of the giant impact is required to calculate the vapor mass fraction (VMF) of the modeled protolunar disk. Recently, a new version of M-ANEOS (Stewart M-ANEOS) was released with an improved treatment of heat capacity and expanded experimental Hugoniot. Here, we compare this new M-ANEOS version with a previous version (N-SPH M-ANEOS) and assess the resulting differences in smoothed particle hydrodynamics (SPH) simulations. We find that Stewart M-ANEOS results in cooler disks with smaller values of VMF and in differences in disk mass that are dependent on the initial impact angle. We also assess the implications of the minimum "cutoff" density (ρ c ), similar to a maximum smoothing length, that is set as a fast-computing alternative to an iteratively calculated smoothing length. We find that the low particle resolution of the disk typically results in >40% of disk particles falling to ρ c , influencing the dynamical evolution and VMF of the disk. Our results show that the choice of EoS, ρ c , and particle resolution can cause the VMF and disk mass to vary by tens of percent. Moreover, small values of ρ c produce disks that are prone to numerical instability and artificial shocks. We recommend that future giant impact SPH studies review smoothing methods and ensure the thermodynamic stability of the disk over simulated time.

Keywords: earth-moon system; hydrodynamical simulations; impact phenomena; the moon; astrophysical fluid dynamics; planetary-disk interactions; natural satellite formation
Masses and Densities of Dwarf Planet Satellites Measured with ALMA

We have used the Atacama Large Millimeter/submillimeter Array to measure precise absolute astrometric positions and detect the astrometric wobble of dwarf planet Orcus and its satellite Vanth over a complete orbit. We also place upper limits to the astrometric wobble induced by Dysnomia on dwarf planet Eris around its orbit. From the Vanth-Orcus barycentric motion, we find a Vanth-Orcus mass ratio of 0.16 ± 0.02-the highest of any known planet or dwarf planet. This large ratio is consistent with the hypothesis that Vanth is a largely intact impactor from a giant collision in the system and that the system has likely evolved to a double synchronous state. We find only an upper limit of the barycenter motion of Eris, which implies a 1σ upper limit to the Dysnomia-Eris mass ratio of 0.0085, close to the modeled transition region between giant impact generated satellites, which are largely intact remnants of the original impactor and those which form out of reaccreted disk material left over postimpact. The low albedo of Dysnomia leads us to marginally favor the intact impactor scenario. We find that Dysnomia has a density of <1.2 g cm-3, significantly lower than the 2.4 g cm-3 of Eris.

Keywords: dwarf planets; radio astrometry; natural satellite formation
Coaque: An Astronomical Icon in the Middle of the World

This study aims to contribute to the astronomical studies for the creation of the astronomical and archaeological museum in Ecuador. Coaque, a fishermen village in the north coastal of Ecuador, is an iconic place where astronomy and archeology converge and portrays the geodesic and astronomical history of Ecuador. The 16th Century ethnohistorical data is rich on descriptions about abundance of wealth and land fertility within equinoctial zones. This awoke the curiosity of Europeans on the geodesic position. Two centuries later, La Condamine and Bouguer of the French-Hispanic Geodesic Mission, first measured the zero-degrees latitude at Punta Palmar, just south of Coaque. We present the detectability of the Crab Nebula, a high energy TeV source revealing the potential for astroparticles field of study. Also, we clarified the wrong idea of the equilibrium of an egg at zero latitude, a popular misinterpreted physical phenomenon. * AAS 237 HDV on 2021 January, 5th.

Keywords: particle astrophysics; history of astronomy; geodesics
Gradual Sequestration of Water at Lunar Polar Conditions due to Temperature Cycles

Migration of water molecules into the porous lunar soil can lead to sequestration of adsorbed water or ice at depth. Here, this process is modeled at several potential landing sites in the south polar region of the Moon. Desorption times are parameterized based on the Brunauer-Emmett-Teller (BET) isotherm model. Water sequestration is significant at depths where subsurface temperatures remain below the cold-trapping threshold, a condition satisfied at one of three sites considered, west of Haworth Crater. Model calculations predict a hydrated layer below a desiccated layer. The thickness of the desiccated layer is on the scale of the thermal skin depth, which for dust is typically centimeters. The underlying layer, decimeters thick, can be hydrated over a timescale of a billion years, reaching abundances on the order of 1 wt%. This sequestration process potentially simultaneously explains excess hydrogen concentrations outside of cold traps and the observed presence of a desiccated layer above a hydrogenous layer.

Keywords: lunar science; lunar surface; the moon; surface ices; ice formation
Two High-amplitude δ Scuti–γ Doradus Hybrids Constrained by the Radial Fundamental p and Equally Spaced g Modes

Based on 2 minutes cadence TESS data, we investigate pulsations of TIC 65138566 and TIC 139729335 and discover them to be two new high-amplitude δ Scuti stars with equally spaced g modes. We recognize the radial fundamental mode f 1 = 18.3334 c d‑1 and the first overtone f 3 = 23.6429 c d‑1 for TIC 65138566, and identify the highest peak f 1 = 19.0955 c d‑1 as the radial fundamental mode for TIC 139729335. For g modes, both stars display a regular period spacing of 2413 s. Through detailed seismological analysis, we deduce that these period-spacing patterns correspond to modes with ℓ = 1. Moreover, our analysis reveals that with increases in masses and metallicities, the star should display a higher degree of evolution to match a specific period spacing Π0. Conversely, the star should have a lower extent of evolution to match the radial fundamental mode. These two contradictory behaviors allow us to precisely obtain stellar physical parameters. TIC 65138566 and TIC 139729335 are determined to be two main-sequence stars that have almost the same range of masses and metallicities, with M = 1.36 ± 0.06 M ⊙ and Z = 0.005 ± 0.002. The hydrogen abundance in the core of TIC 65138566 is estimated to be about 0.28, while TIC 139729335 has a slightly higher value of around 0.31. Finally, we suggest that the high-amplitude δ Scuti–γ Doradus star TIC 308396022 is a main-sequence star with M = 1.54 ± 0.08 M ⊙, Z = 0.007 ± 0.001, and X c = 0.18 ± 0.02.

Keywords: asteroseismology; delta scuti variable stars; gamma doradus variable stars
A Recipe for the Geophysical Exploration of Enceladus

Orbital geophysical investigations of Enceladus are critical to understanding its energy budget. In this paper, we identified key science questions for the geophysical exploration of Enceladus, answering which would support future assessment of Enceladus' astrobiological potential. Using a Bayesian framework, we explored how science requirements map to measurement requirements. We performed mission simulations to study the sensitivity of single-spacecraft and dual-spacecraft configurations to static gravity and tidal Love numbers of Enceladus. We find that mapping Enceladus' gravity field, improving the accuracy of the physical libration amplitude, and measuring Enceladus' tidal response would provide critical constraints on the internal structure and establish a framework for assessing Enceladus' long-term habitability. This kind of investigation could be carried out as part of a life search mission at little additional resource requirements.

Keywords: planetary interior; gravitational fields; saturnian satellites; space observatories; astrodynamics
The Intermediate Polar FO Aquarii Has Not Been the Same Since Recovering from a Series of Low States

FO Aqr is a bright intermediate polar that has long displayed large amplitude photometric variations corresponding to the 20.9 minutes spin period of its white dwarf. Between 2016 and 2020, the system suffered a series of unprecedented low-states, but recent data shows that it has now recovered to its normal optical luminosity. We compare the light curves obtained by K2/Kepler in 2014 with photometry from the TESS mission obtained in 2021. We find that the spin pulse that had been the dominant feature of the light curve in 2014 is now weak over the second half of the binary orbit and that a beat pulse is enhanced in the TESS photometry. Variations at approximately twice the spin frequency are now seen over the second half of the orbit. These photometric properties may be the new normal for FO Aqr now that its white dwarf has begun to spin down.

Keywords: cataclysmic variable stars; dq herculis stars; white dwarf stars; magnetic variable stars
Gravitomagnetic Instabilities of Relativistic Magnetohydrodynamics

We study gravitomagnetic instabilities of a static homogeneous medium with an aligned magnetic field in the two contexts of relativistic magnetohydrodynamics (MHD): first, MHD with post-Newtonian (PN) corrections, and second, special relativistic (SR) MHD with weak gravity. The analysis in the PN MHD is made without taking the temporal gauge condition, thus results are gauge-invariant. The PN corrections of the internal energy, pressure, sound velocity, and the Alfvén velocity lower the critical (Jeans) wavelength. All relativistic effects tend to destabilize the system. Although the SR MHD with weak gravity is presented in the harmonic gauge, in the presence of gravity the stability analysis is strictly valid to Newtonian order. In the absence of gravity, the SR MHD is independent of the gauge condition. We present the plane wave velocities and the stability criteria in both cases.

Keywords: gravitation; gravitational instability; magnetohydrodynamics; relativity
Interstellar Neutral Hydrogen in the Heliosphere: New Horizons Observations in the Context of Models

Interstellar neutral (ISN) hydrogen is the most abundant species in the outer heliosheath and the very local interstellar medium (VLISM). Charge-exchange collisions in the outer heliosheath result in filtration, reducing the ISN hydrogen density inside the heliosphere. Additionally, these atoms are intensively ionized close to the Sun, resulting in a substantial reduction of their density within a few astronomical units from the Sun. The products of this ionization—pickup ions (PUIs)—are detected by charged particle detectors. The Solar Wind Around Pluto instrument on New Horizons provides, for the first time, PUI observations from the distant heliosphere. We analyze the observations collected between 22 and 52 au from the Sun to find the ISN hydrogen density profile and compare the results with predictions from global heliosphere models. We conclude that the density profile derived from the observations is inconsistent with steady-state model predictions. This discrepancy is not explained by time variations close to the Sun and thus may be related to the temporal evolution of the outer boundaries or VLISM conditions. Furthermore, we show that the cold and hot models of ISN hydrogen distribution are not a good approximation closer to the termination shock. Therefore, we recommend a new fiduciary point based on the available New Horizons observations at 40 au from the Sun, at ecliptic direction (285.°62, 1.°94), where the ISN hydrogen density is 0.11 cm‑3. The continued operation of New Horizons should give better insight into the source of the discussed discrepancy.

Keywords: interstellar atomic gas; interstellar medium; heliosphere; interstellar medium wind; interplanetary physics; pickup ions; solar wind termination; collision physics; charge transfer
Catalog of Ultraviolet Bright Stars: Strategies for UV Occultation Measurements, Planetary Illumination Modeling, and Sky Map Analyses Using Hybrid IUE-Kurucz Spectra

Ultraviolet spectroscopy is a powerful method to study planetary surface composition through reflectance measurements, atmospheric composition through stellar/solar occultations, transits of other planetary bodies, and direct imaging of airglow and auroral emissions. The next generation of ultraviolet spectrographs (UVS) on board ESA's Jupiter Icy Moons Explorer and NASA's Europa Clipper missions will perform such measurements of Jupiter and its moons in the early 2030s. This work presents a compilation of a detailed UV stellar catalog, named Catalog of Ultraviolet Bright Stars (CUBS), of targets with high intensity in the 50–210 nm wavelength range with applications relevant to planetary spectroscopy. These applications include (1) planning and simulating occultations, including calibration measurements; (2) modeling starlight illumination of dark, nightside planetary surfaces primarily lit by the sky; and (3) studying the origin of diffuse Galactic UV light as mapped by existing data sets from Juno-UVS and others. CUBS includes observations from the International Ultraviolet Explorer (IUE) and additional information from the SIMBAD database. We have constructed model spectra at 0.1 nm resolution for almost 90,000 targets using interpolated Kurucz models (which have a resolution of 1 nm) and, when available, IUE spectra. CUBS also includes robust checks for agreement between the Kurucz models and the IUE data. We also present a tool for which our catalog can be used to identify the best candidates for stellar occultation observations, with applications for any UV instrument. We report on our methods for producing CUBS and discuss plans for its implementation during ongoing and upcoming planetary missions.

Keywords: ultraviolet spectroscopy; catalogs; europa; stellar occultation
Environmental Effects in Herschel Observations of the Ionized Carbon Content of Star-forming Dwarf Galaxies in the Virgo Cluster

We use archival Herschel data to examine the singly ionized carbon ([C II]) content of 14 star-forming dwarf galaxies in the Virgo cluster. We use spectral energy distribution fits to far-infrared, mid-infrared, near-infrared, optical, and ultraviolet data to derive the total infrared continuum (TIR) for these galaxies. We compare the [C II]/TIR ratio for dwarf galaxies in the central part of Virgo to those in the southern part of the cluster and to galaxies with similar TIR luminosities and metallicities in the Herschel Dwarf Galaxy Survey (DGS) sample of field dwarf galaxies to look for signs of [C II] formation independent of star formation. Our analysis indicates that the sample of Virgo dwarfs in the central part of the cluster has significantly higher values of [C II]/TIR than the sample from the southern part of the cluster and the sample from the DGS, while the southern sample is consistent with the DGS. This [C II]/TIR excess implies that a significant fraction of the [C II] in the dwarf galaxies in the cluster center has an origin other than star formation and is likely to be due to environmental processes in the central part of the cluster. We also find a surprisingly strong correlation between [C II]/TIR and the local ram pressure felt by the dwarf galaxies in the cluster. In this respect, we claim that the excess [C II] we see in these galaxies is likely to be due to formation in ram-pressure shocks. * Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Keywords: virgo cluster; ram pressure stripped tails; far infrared astronomy; cii region; dwarf galaxies