adsabs/SciX_UAT_keywords huggingface dataset:
Carbon Cycling and Habitability of Massive Earth-like Exoplanets

As the number of detected rocky extrasolar planets increases, the question of whether their surfaces could be habitable is becoming more pertinent. On Earth, the long-term carbonate-silicate cycle is able to regulate surface temperatures over timescales larger than one million years. Elevated temperatures enhance weathering, removing CO2 from the atmosphere, which is subducted into the mantle. At mid-ocean ridges, CO2 is supplied to the atmosphere from the interior. The carbon degassing flux is controlled by the melting depth beneath mid-ocean ridges and the spreading rate, influenced by the pressure- and temperature-dependent mantle viscosity. The influences of temperature and pressure on mantle degassing become increasingly important for more massive planets. Here, we couple a thermal evolution model of Earth-like planets of different masses with a model of the long-term carbon cycle and assess their surface temperature evolution. We find that the spreading rate at 4.5 Gyr increases with planetary mass up to 3 Earth masses, since the temperature dependence of viscosity dominates over its pressure dependency. For higher-mass planets, pressure dependence dominates and the plates slow down. In addition, the effective melting depth at 4.5 Gyr as a function of planetary mass has its maximum at 3 M⊕. Altogether, at 4.5 Gyr, the degassing rate and therefore surface temperature have their maximum at 3 M⊕. This work emphasizes that both age and mass should be considered when predicting the habitability of exoplanets. Despite these effects, the long-term carbon cycle remains an effective mechanism that regulates the surface temperature of massive Earth-like planets.

Keywords: exoplanets; super earths; habitable planets; mantle; plate tectonics
The Advanced Spectral Library (ASTRAL): Abundance Analysis of the Chemically Peculiar Star HR 465

This paper presents the results of the spectrum analysis of the B-type magnetic chemically peculiar star HR 465. HR 465 shows unusual abundance patterns that vary with a period of 21.5 yr. Our observations are recorded at φ = 0.45, 0.68, and 0.85 of the spectroscopic period, where φ = 0 represents the phase of maximum flux in the photometric y-band. Synthetic spectra, computed using an LTE atmosphere model, are fit to high-resolution ultraviolet Hubble Space Telescope (φ = 0.45) spectra obtained as part of the Advanced Spectral Library Project: Hot Stars program. The ultraviolet data are supplemented by high-resolution optical spectra (φ = 0.68 and 0.85) recorded at the Nordic Optical Telescope with the SOFIN spectrograph. The optical data are used as a complement to the high line-density ultraviolet spectrum to derive accurate abundances for elements without spectral lines in the ultraviolet and to improve the abundance phase coverage for many atoms/ions. This analysis presents abundance results for more than 70 atoms/ions and confirms parts of the abundance characteristics previously reported where elements with high mass numbers show significant abundance enhancements compared with solar values while some of the lighter elements show abundance deficiencies. In addition, our measured abundances are consistent with the periodic variability for chromium and rare-earth elements. Our results are compared with earlier investigations of this peculiar object to constrain stellar abundance and diffusion. * Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Keywords: chemically peculiar stars; stellar abundances; bp stars; high resolution spectroscopy; astronomy data modeling
Core-collapse Supernova Simulations with Reduced Nucleosynthesis Networks

We present core-collapse supernova simulations including nuclear reaction networks that impact explosion dynamics and nucleosynthesis. The different composition treatment can lead to changes in the neutrino heating in the vicinity of the shock by modifying the number of nucleons and thus the neutrino-opacity of the region. This reduces the ram pressure outside the shock and allows an easier expansion. The energy released by the nuclear reactions during collapse also slows down the accretion and aids the shock expansion. In addition, nuclear energy generation in the postshocked matter produces up to 20% more energetic explosions. Nucleosynthesis is affected due to the different dynamic evolution of the explosion. Our results indicate that the energy generation from nuclear reactions helps to sustain late outflows from the vicinity of the proto-neutron star, synthesizing more neutron-rich species. Furthermore, we show that there are systematic discrepancies between the ejecta calculated with in situ and ex situ reaction networks. These differences stem from the intrinsic characteristics of evolving the composition in hydrodynamic simulations or calculating it with Lagrangian tracer particles. The mass fractions of some Ca, Ti, Cr, and Fe isotopes are consistently underproduced in postprocessing calculations, leading to different nucleosynthesis paths. Our results suggest that large in situ nuclear reaction networks are important for a realistic feedback of the energy generation, the neutrino heating, and a more accurate ejecta composition.

Keywords: core-collapse supernovae; supernovae; explosive nucleosynthesis; supernova dynamics; astrophysical explosive burning; nuclear astrophysics
The Bombardment History of the Giant Planet Satellites

The origins of the giant planet satellites are debated, with scenarios including formation from a protoplanetary disk, sequential assembly from massive rings, and recent accretion after major satellite–satellite collisions. Here, we test their predictions by simulating outer solar system bombardment and calculating the oldest surface ages on each moon. Our crater production model assumes the projectiles originated from a massive primordial Kuiper Belt (PKB) that experienced substantial changes from collisional evolution, which transformed its size frequency distribution into a wavy shape, and Neptune's outward migration, which ejected most PKB objects onto destabilized orbits. The latter event also triggered an instability among the giant planets some tens of Myr after the solar nebula dispersed. We find all giant planet satellites are missing their earliest crater histories, with the likely source being impact resetting events. Iapetus, Hyperion, Phoebe, and Oberon have surface ages that are a few Myr to a few tens of Myr younger than when Neptune entered the PKB (i.e., they are 4.52–4.53 Gyr old). The remaining midsized satellites of Saturn and Uranus, as well as the small satellites located between Saturn's rings and Dione, have surfaces that are younger still by many tens to many hundreds of Myr (4.1–4.5 Gyr old). A much wider range of surface ages are found for the large moons Callisto, Ganymede, Titan, and Europa (4.1, 3.4, 1.8, and 0.18 Gyr old, respectively). At present, we favor the midsized and larger moons forming within protoplanetary disks, with the other scenarios having several challenges to overcome.

Keywords: collisional processes; planetary migration; natural satellite evolution; natural satellite formation; galilean satellites; saturnian satellites; uranian satellites; natural satellite surfaces; kuiper belt; trans-neptunian objects; comet dynamics; planetary system evolution
Magnetic Field Structure, Doppler Shift, and Intensity of Active Regions and Their Connections with the Solar Wind

The properties of active regions and their connections with the solar wind are important issues. In this study, nine isolated active regions near the solar disk center were chosen. The relationships between blueshift, intensity, magnetic concentrated areas (MCAs), and the potential-field source-surface (PFSS) open magnetic field of active regions were analyzed. Whether an active region contributes to the solar wind was identified only based on the relationship between the properties of in situ solar wind and the large structure of the corona. Then the two phenomena (blueshift and PFSS open magnetic field) for inferring whether an active region contributes to the solar wind were tested. We find that the blueshift areas appear in all cases and the average Doppler speed ranges from -6 to -23 km s-1. The blueshift areas generally root inside MCAs and are far from the neutral lines. The intensity of blueshift areas negatively correlates with the blueshift speed. Statistically, 10 of 16 blueshift areas are associated with the PFSS open magnetic field lines, and all 10 PFSS open magnetic field areas are accompanied by blueshift. We demonstrate that a polarity of an active region generally contributes to the solar wind if it is associated with a PFSS open magnetic field. There are 9 of 10 (13 of 16) PFSS open magnetic field areas (blueshift regions) associated with the solar wind. The results of this study should help determine the observation target of SPICE on board the Solar Orbiter whose scientific goal is connecting the Sun and the heliosphere.

Keywords: solar wind; solar surface; solar active regions; solar physics
Reflected Light Observations of the Galilean Satellites from Cassini: A Test Bed for Cold Terrestrial Exoplanets

For terrestrial exoplanets with thin or no atmospheres, the surface contributes light to the reflected light signal of the planet. Measurement of the variety of disk-integrated brightnesses of bodies in the solar system and the variation with illumination and wavelength is essential for both planning imaging observations of directly imaged exoplanets and interpreting the eventual data sets. Here we measure the change in brightness of the Galilean satellites as a function of planetocentric longitude, illumination phase angle, and wavelength. The data span a range of wavelengths from 400 to 950 nm and predominantly phase angles from 0° to 25°, with some constraining observations near 60°-140°. Despite the similarity in size and density between the moons, surface inhomogeneities result in significant changes in the disk-integrated reflectivity with planetocentric longitude and phase angle. We find that these changes are sufficient to determine the rotational periods of the moon. We also find that at low phase angles, the surface can produce reflectivity variations of 8%-36%, and the limited high phase angle observations suggest variations will have proportionally larger amplitudes at higher phase angles. Additionally, all of the Galilean satellites are darker than predicted by an idealized Lambertian model at the phases most likely to be observed by direct imaging missions. If Earth-sized exoplanets have surfaces similar to that of the Galilean moons, we find that future direct imaging missions will need to achieve precisions of less than 0.1 ppb. Should the necessary precision be achieved, future exoplanet observations could exploit similar observation schemes to deduce surface variations, determine rotation periods, and potentially infer surface composition.

Keywords: galilean satellites; exoplanet surface characteristics; exoplanet atmospheres
Detection Capability of Flux Ropes during the Solar Orbiter Mission

Flux ropes are interplanetary magnetic helical structures that are receiving increasing attention because of their likely role in magnetohydrodynamic (MHD) processes as well as their impact on space weather science. A very promising and powerful approach to address their investigation and characterization is based on wavelet spectrograms of the invariants of the ideal MHD equations. The accuracy of this method to infer flux rope properties depends on the proper evaluation of the direction of propagation of the flux rope itself, which is often difficult to assess. We present a numerical test of the reliability of this diagnostic technique, by simulating a synthetic flux rope of fixed size and propagation direction along the Solar Orbiter orbit, that is very elongated and inclined with respect to the orbital plane. We find that when the flux rope is crossed for less than 50% of its width, the procedure becomes unreliable. Quantitative information on how to properly recover the flux-rope intrinsic properties is provided.

Keywords: magnetohydrodynamics; wavelet analysis; astrostatistics techniques; interplanetary turbulence; space vehicles; orbiters; solar coronal mass ejections; solar wind; interplanetary medium
An Analysis Pipeline for CHIME/FRB Full-array Baseband Data

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has become a leading facility for detecting fast radio bursts (FRBs) through the CHIME/FRB backend. CHIME/FRB searches for fast transients in polarization-summed intensity data streams that have 24 kHz spectral and 1 ms temporal resolution. The intensity beams are pointed to predetermined locations in the sky. A triggered baseband system records the coherent electric field measured by each antenna in the CHIME array at the time of FRB detections. Here we describe the analysis techniques and automated pipeline developed to process these full-array baseband data recordings. Whereas the real-time FRB detection pipeline has a localization limit of several arcminutes, offline analysis of baseband data yields source localizations with subarcminute precision, as characterized by using a sample of pulsars and one repeating FRB with known positions. The baseband pipeline also enables resolving temporal substructure on a microsecond scale and the study of polarization including detections of Faraday rotation.

Keywords: algorithms; radio interferometry; radio interferometers; radio transient sources; radio telescopes; radio astrometry; radio bursts; extragalactic radio sources; pointing accuracy; high time resolution astrophysics
Heat-flux-limited Cloud Activity and Vertical Mixing in Giant Planet Atmospheres with an Application to Uranus and Neptune

Storms operated by moist convection and the condensation of CH4 or H2S have been observed on Uranus and Neptune. However, the mechanism of cloud formation, thermal structure, and mixing efficiency of ice giant weather layers remains unclear. In this paper, we show that moist convection is limited by heat transport on giant planets, especially on ice giants where planetary heat flux is weak. Latent heat associated with condensation and evaporation can efficiently bring heat across the weather layer through precipitations. This effect was usually neglected in previous studies without a complete hydrological cycle. We first derive analytical theories and show that the upper limit of cloud density is determined by the planetary heat flux and microphysics of clouds but is independent of the atmospheric composition. The eddy diffusivity of moisture depends on the planetary heat fluxes, atmospheric composition, and surface gravity but is not directly related to cloud microphysics. We then conduct convection- and cloud-resolving simulations with SNAP to validate our analytical theory. The simulated cloud density and eddy diffusivity are smaller than the results acquired from the equilibrium cloud condensation model and mixing length theory by several orders of magnitude but consistent with our analytical solutions. Meanwhile, the mass-loading effect of CH4 and H2S leads to superadiabatic and stable weather layers. Our simulations produced three cloud layers that are qualitatively similar to recent observations. This study has important implications for cloud formation and eddy mixing in giant planet atmospheres in general and observations for future space missions and ground-based telescopes.

Keywords: neptune; uranus; solar system gas giant planets; atmospheric dynamics; atmospheric clouds; planetary atmospheres
Tidal Dissipation in Dual-body, Highly Eccentric, and Nonsynchronously Rotating Systems: Applications to Pluto-Charon and the Exoplanet TRAPPIST-1e

Using the Andrade-derived Sundberg-Cooper rheology, we apply several improvements to the secular tidal evolution of TRAPPIST-1e and the early history of Pluto-Charon under the simplifying assumption of homogeneous bodies. By including higher-order eccentricity terms (up to and including e20), we find divergences from the traditionally used e2 truncation starting around e = 0.1. Order-of-magnitude differences begin to occur for e > 0.6. Critically, higher-order eccentricity terms activate additional spin-orbit resonances. Worlds experiencing nonsynchronous rotation can fall into and out of these resonances, altering their long-term evolution. Nonzero obliquity generally does not generate significantly higher heating; however, it can considerably alter orbital and rotational evolution. Much like eccentricity, obliquity can activate new tidal modes and resonances. Tracking the dual-body dissipation within Pluto and Charon leads to faster evolution and dramatically different orbital outcomes. Based on our findings, we recommend future tidal studies on worlds with e ≥ 0.3 to take into account additional eccentricity terms beyond e2. This threshold should be lowered to e > 0.1 if nonsynchronous rotation or nonzero obliquity is under consideration. Due to the poor convergence of the eccentricity functions, studies on worlds that may experience very high eccentricity (e ≥ 0.6) should include terms with high powers of eccentricity. We provide these equations up to e10 for arbitrary obliquity and nonsynchronous rotation. Finally, the assumption that short-period, solid-body exoplanets with e ≳ 0.1 are tidally locked in their 1:1 spin-orbit resonance should be reconsidered. Higher-order spin-orbit resonances can exist even at these relatively modest eccentricities, while previous studies have found such resonances can significantly alter stellar-driven climate.

Keywords: tidal friction; orbital theory; exoplanet tides; exoplanet evolution
Improving Solar Energetic Particle Event Prediction through Multivariate Time Series Data Augmentation

Solar energetic particles (SEPs) are associated with extreme solar events that can cause major damage to space- and ground-based life and infrastructure. High-intensity SEP events, particularly ∼100 MeV SEP events, can pose severe health risks for astronauts owing to radiation exposure and affect Earth's orbiting satellites (e.g., Landsat and the International Space Station). A major challenge in the SEP event prediction task is the lack of adequate SEP data because of the rarity of these events. In this work, we aim to improve the prediction of ∼30, ∼60, and ∼100 MeV SEP events by synthetically increasing the number of SEP samples. We explore the use of a univariate and multivariate time series of proton flux data as input to machine-learning-based prediction methods, such as time series forest (TSF). Our study covers solar cycles 22, 23, and 24. Our findings show that using data augmentation methods, such as the synthetic minority oversampling technique, remarkably increases the accuracy and F1-score of the classifiers used in this research, especially for TSF, where the average accuracy increased by 20%, reaching around 90% accuracy in the ∼100 MeV SEP prediction task. We also achieved higher prediction accuracy when using the multivariate time series data of the proton flux. Finally, we build a pipeline framework for our best-performing model, TSF, and provide a comprehensive hierarchical classification of the ∼100, ∼60, and ∼30 MeV and non-SEP prediction scenarios.

Keywords: solar energetic particles; time series analysis; multivariate analysis; heliosphere
Chandra Observations of NGC 7212: Large-scale Extended Hard X-Ray Emission

Recent observations of nearby Compton thick (CT) active galactic nuclei (AGNs) with Chandra have resolved hard (>3 keV) X-ray emission extending out from the central supermassive black hole to kiloparsec scales, challenging the long-held belief that the characteristic hard X-ray continuum and fluorescent Fe K lines originate in the inner ∼parsec due to the excitation of obscuring material. In this paper we present the results of the most recent Chandra ACIS-S observations of NGC 7212, a CT AGN in a compact group of interacting galaxies, with a total effective exposure of ∼150 ks. We find ∼20% of the observed emission is found outside of the central kiloparsec, with ∼17% associated with the soft X-rays, and ∼3% with hard X-ray continuum and Fe K line. This emission is extended both along the ionization cone and in the cross-cone direction up to ∼3.8 kpc scales. The spectrum of NGC 7212 is best represented by a mixture of thermal and photoionization models that indicate the presence of complex gas interactions. These observations are consistent with what is observed in other CT AGN (e.g., ESO 428-G014, NGC 1068), providing further evidence that this may be a common phenomenon. High-resolution observations of extended CT AGN provide an especially valuable environment for understanding how AGN feedback impacts host galaxies on galactic scales.

Keywords: active galaxies; x-ray active galactic nuclei; agn host galaxies
A 1201 s Orbital Period Detached Binary: The First Double Helium Core White Dwarf LISA Verification Binary

We report the discovery of a 1201 s orbital period binary, the third shortest-period detached binary known. Sloan Digital Sky Survey J232230.20 + 050942.06 contains two He-core white dwarfs orbiting with a 27° inclination. Located 0.76 kpc from the Sun, the binary has an estimated Laser Interferometer Space Antenna (LISA) 4 yr signal-to-noise ratio of 40. J2322 + 0509 is the first He + He white dwarf LISA verification binary, a source class that is predicted to account for one-third of resolved LISA ultra-compact binary detections.

Keywords: compact binary stars; da stars; dc stars; gravitational wave sources; gravitational waves; white dwarf stars; compact objects; detached binary stars
Methanol Formation through Reaction of Low-energy CH3 + Ions with an Amorphous Solid Water Surface at Low Temperature

We have performed experimental investigations of methanol formation via the reactions of low-energy CH3 + ions with an amorphous solid water (ASW) surface at ~10 K. A newly developed experimental apparatus enabled irradiation of the ASW surface by several eV ions and detection of trace amounts of reaction products on the surface. It was found that methanol molecules were produced by low-energy CH3 + irradiation of the ASW surface and that hydroxy groups in the produced methanol originated from water molecules in the ASW, as predicted in a previous theoretical study. Little temperature dependence of the observed methanol intensity is apparent in the temperature range 12-60 K. Ab initio molecular dynamics simulations under constant-temperature conditions of 10 K suggested that this reaction spontaneously produced a methanol molecule and an H3O+ ion, regardless of the contact point of CH3 + on the ASW surface. We have performed a simulation with an astrochemical model under molecular-cloud conditions, where the reaction between CH3 + and H2O ice, leading to methanol formation, was included. We found that the impact of the reaction on methanol abundance was limited only at the edge of the molecular cloud (<1 mag) because of the low abundance of CH3 + in the gas phase, whereas the reaction between the abundant molecular ion (HCO+) and H2O ice, which has not yet been confirmed experimentally, can considerably affect the abundance of a complex organic molecule. This work sheds light on a new type of reaction between molecular ions and ice surfaces that should be included in astrochemical models.

Keywords: astrochemistry; molecular reactions; ion-neutral reactions; molecular physics; interstellar dust processes