adsabs/SciX_UAT_keywords huggingface dataset:
Detectability of Ultra-compact X-Ray Binaries as LISA Sources

Ultra-compact X-ray binaries (UCXBs) are low-mass X-ray binaries with ultra-short orbital periods (usually less than 1 hr) and hydrogen-poor donor stars, which are proposed to be potential Laser Interferometer Space Antenna (LISA) sources. In this work, we first employ the Modules for Experiments in Stellar Astrophysics code to examine the parameter space of the progenitors of UCXBs that LISA will detect. Our simulations indicate that the initial binaries with a neutron star and a $0.4\mbox{--}3.5\,{M}_{\odot }$ companion star, in an orbit of initial orbital period smaller than the bifurcation period, could evolve into UCXBs, some of which will emit gravitational wave signals that can be detectable by LISA. However, the initial orbital periods of the binaries that will evolve into UCXB-LISA sources in a distance of 10 kpc are located in a very narrow range, i.e., the formation of these LISA source requires an extreme fine-tuning of initial parameter. According to the characteristic strains and the derived maximum detectable distances, four sources among eight UCXBs with the observed distances are expected to be detected by LISA. Based on the parameter space given by the detailed binary evolution models and the rapid binary star evolution code, the birthrate of UCXBs appearing as LISA sources in the Galaxy is estimated to be $(2\mbox{--}2.6)\times {10}^{-6}\,{\mathrm{yr}}^{-1}$. Considering the contribution of UCXBs in globular clusters, the number of UCXB-LISA sources can reach 240-320. Although the formation condition is severe, the detectability of UCXBs by LISA is still significant because it provides an opportunity to pursue full multi-messenger investigations.

Keywords: gravitational wave sources; gravitational waves; x-ray binary stars; compact binary stars; stellar evolution
Jupiter Atmospheric Models and Outer Boundary Conditions for Giant Planet Evolutionary Calculations

We present updated atmospheric tables suitable for calculating the post-formation evolution and cooling of Jupiter and Jupiter-like exoplanets. These tables are generated using a 1D radiative transfer modeling code that incorporates the latest opacities and realistic prescriptions for stellar irradiation and ammonia clouds. To ensure the accuracy of our model parameters, we calibrate them against the measured temperature structure and geometric albedo spectrum of Jupiter, its effective temperature, and its inferred internal temperature. As a test case, we calculate the cooling history of Jupiter using an adiabatic and homogeneous interior and compare with extant models now used to evolve Jupiter and the giant planets. We find that our model reasonably matches Jupiter after evolving a hot-start initial condition to the present age of the solar system, with a discrepancy in brightness temperature/radius within 2%. Our algorithm allows us to customize for different cloud, irradiation, and metallicity parameters. This class of boundary conditions can be used to study the evolution of solar system giant planets and exoplanets with more complicated interior structures and nonadiabatic, inhomogeneous internal profiles.

Keywords: extrasolar gaseous giant planets; solar system gas giant planets; jupiter; exoplanet atmospheres; planetary atmospheres
Tidal Heating at Europa Using the Multifrequency Analysis of Tidal Heating Toolkit

We evaluate the thermal response of Europa's ice shell to the gravity perturbation of Jupiter using a comprehensive toolkit (dubbed Multifrequency Analysis of Tidal Heating, MATH) that evaluates tidal heating and heat flow in planetary bodies. The tidal heating source is radially resolved and can capture the temperature-dependent pattern of heat production with depth. We use MATH to examine the steady-state thermal profiles through a conductive Europan ice shell, considering the tidal effects of long-term eccentricity variations, obliquity, libration, and nonsynchronous rotation (NSR). In each case, we vary the shell thickness, calculate the combination of tidal heating generated within the shell and heat flux into the shell base that would maintain that thickness, and track the resulting surface heat flux. We find that Europa's ice shell should be, on average, no more than 12-17 km thick, due to long-term eccentricity variations, and could be even thinner if the basal heat flux is nonnegligible. These results are more consistent with inferences from Europa's surface geology than previous tidal heating studies that used simplified interior models, a globally averaged tidal heating rate, and/or constant eccentricity. We also find that, for a given stable shell thickness, the surface heat flow remains fairly consistent even as other parameters are varied, perhaps providing an additional method for constraining ice shell thicknesses on ocean-bearing moons. Although Europa's tidal heat budget and shell thickness seem relatively insensitive to constant obliquity, libration, and NSR, moons in closer-in orbits may be more sensitive to these other effects and should be further explored.

Keywords: tides; europa
Detection of Metal Enrichment by SN 2011jm in NGC 4809

Cosmic metals are believed to originate from stellar and supernovae (SNe) nucleosynthesis, dispersed into the interstellar medium (ISM) through stellar winds and supernova explosions. In this paper, we present the clear evidence of metal enrichment by a Type Ic SN 2011jm in the galaxy NGC 4809, utilizing high spatial resolution integral field unit observations obtained from the Very Large Telescope/Multi Unit Spectroscopic Explorer. Despite SN 2011jm being surrounded by metal-deficient ISM (∼0.25 Z ⊙) at a scale about 100 pc, we clearly detect enriched oxygen abundance (∼0.35 Z ⊙) and a noteworthy nitrogen-to-oxygen ratio at the SN site. Remarkably, the metal pollution is confined to a smaller scale (≲13 pc). We posit that the enhanced ionized metal stems from stellar winds emitted by massive stars or previous SN explosions. This observation may represent the first direct detection of chemical pollution by stellar feedback in star-forming galaxies beyond the Local Volume.

Keywords: metallicity; interstellar medium; type ic supernovae; dwarf irregular galaxies
Light Curves and Event Rates of Axion Instability Supernovae

It was recently proposed that exotic particles can trigger a new stellar instability that is analogous to the e - e + pair instability if they are produced and reach equilibrium in the stellar plasma. In this study, we construct axion instability supernova (AISN) models caused by the new instability to predict their observational signatures. We focus on heavy axion-like particles (ALPs) with masses of ~400 keV-2 MeV and coupling with photons of g a γ ~ 10-5 GeV-1. It is found that the 56Ni mass and the explosion energy are significantly increased by ALPs for a fixed stellar mass. As a result, the peak times of the light curves of AISNe occur earlier than those of standard pair-instability supernovae by 10-20 days when the ALP mass is equal to the electron mass. Also, the event rate of AISNe is 1.7-2.6 times higher than that of pair-instability supernovae, depending on the high mass cutoff of the initial mass function.

Keywords: particle astrophysics; stellar evolution; supernovae
Young, Blue, and Isolated Stellar Systems in the Virgo Cluster. I. 2D Optical Spectroscopy

We use panoramic optical spectroscopy obtained with the Very Large Telescope/MUSE to investigate the nature of five candidate extremely isolated low-mass star-forming regions (Blue Candidates; hereafter, BCs) toward the Virgo cluster of galaxies. Four of the five (BC1, BC3, BC4, and BC5) are found to host several H II regions and to have radial velocities fully compatible with being part of the Virgo cluster. All the confirmed candidates have mean metallicity significantly in excess of that expected from their stellar mass, indicating that they originated from gas stripped from larger galaxies. In summary, these four candidates share the properties of the prototype system SECCO 1, suggesting the possible emergence of a new class of stellar systems, intimately linked to the complex duty cycle of gas within clusters of galaxies. A thorough discussion of the nature and evolution of these objects is presented in a companion paper, where the results obtained here from the MUSE data are complemented with Hubble Space Telescope (optical) and Very Large Array (HI) observations.

Keywords: star forming regions; virgo cluster; intracluster medium; low surface brightness galaxies; ram pressure stripped tails; tidal tails; galaxy interactions
Parkes Transient Events. I. Database of Single Pulses, Initial Results, and Missing Fast Radio Bursts

A large number of observations from the Parkes 64 m diameter radio telescope, recorded with high time resolution, are publicly available. We have reprocessed all of the observations obtained during the first four years (from 1997-2001) of the Parkes Multibeam Receiver system in order to identify transient events, and have built a database that records the 568,736,756 pulse candidates generated during this search. We have discovered a new fast radio burst (FRB), FRB 010305, with a dispersion measure (DM) of 350 ± 5 cm-3 pc and explored why so few FRBs have been discovered in data prior to 2001. After accounting for the dispersion smearing across the channel bandwidth and the sky regions surveyed, the number of FRBs is found to be consistent with model predictions. We also present five single pulse candidates from unknown sources, but with Galactic DMs. We extract a diverse range of sources from the database, which can be used, for example, as a training set of data for new software being developed to search for FRBs in the presence of radio frequency interference.

Keywords: radio transient sources; radio bursts; astronomy databases
Resolving the Fastest Ejecta from Binary Neutron Star Mergers: Implications for Electromagnetic Counterparts

We examine the effect of spatial resolution on initial mass ejection in grid-based hydrodynamic simulations of binary neutron star mergers. The subset of the dynamical ejecta with velocities greater than ~0.6c can generate an ultraviolet precursor to the kilonova on approximately hour timescales and contribute to a years long nonthermal afterglow. Previous work has found differing amounts of this fast ejecta, by one to two orders of magnitude, when using particle-based or grid-based hydrodynamic methods. Here, we carry out a numerical experiment that models the merger as an axisymmetric collision in a corotating frame, accounting for Newtonian self-gravity, inertial forces, and gravitational wave losses. The lower computational cost allows us to reach spatial resolutions as high as 4 m, or ~3 × 10-4 of the stellar radius. We find that fast ejecta production converges to within 10% for a cell size of 20 m. This suggests that fast ejecta quantities found in existing grid-based merger simulations are unlikely to increase to the level needed to match particle-based results upon further resolution increases. The resulting neutron-powered precursors are in principle detectable out to distances ≲200 Mpc with upcoming facilities.We also find that head-on collisions at the freefall speed, relevant for eccentric mergers, yield fast and slow ejecta quantities of order 10-2 M⊙, with a kilonova signature distinct from that of quasi-circular mergers.

Keywords: gravitational waves; hydrodynamics; neutron stars; nuclear astrophysics; shocks; transient sources
Star and Cluster Formation in the Sh2-112 Filamentary Cloud Complex

We present the star formation activity around the emission nebula Sh2-112. At a distance of ~2.1 kpc, this H II complex, itself 3 pc in radius, is illuminated by the massive star (O8 V) BD+45 3216. The associated molecular cloud extends in angular scales of 2.°0 × 0.°83, corresponding to linear sizes of 73 pc by 30 pc, along the Galactic longitude. The high-resolution (30″) extinction map reveals a chain of dust clumps aligned with the filament-like structure with an average extinction of A V ~ 2.78 mag, varying up to a maximum of ~17 mag. Our analysis led to identification of a rich population (~500) of young (average age of ~1 Myr) stars, plus a numerous number (~350) of Hα emitters, spatially correlated with the filamentary clouds. Located near the edge of the cloud, the luminous star BD+45 3216 has created an arc-like pattern as the ionizing radiation encounters the dense gas, forming a blister-shaped morphology. We found three distinct young stellar groups, all coincident with relatively dense parts of the cloud complex, signifying ongoing star formation. Moreover, the cloud filament (excitation temperature ~10 K) traced by the CO isotopologues and extending nearly ~80 pc is devoid of ionized gas except at the dense cores (excitation temperature ~28-32 K) wherein significant ionized emission excited by OB stars (dynamical age ~0.18-1.0 Myr) pertains. The radial velocity is dynamic (median ~-3.65 km s-1) along the main filament, increasing from Galactic east to west, indicating mass flow to form the massive stars/clusters at the central hubs.

Keywords: star formation; star forming regions; h ii regions; pre-main sequence stars; interstellar extinction; molecular clouds; ionization; stellar feedback
Hot Super-Earths with Hydrogen Atmospheres: A Model Explaining Their Paradoxical Existence

In this paper, we propose a new mechanism that could explain the survival of hydrogen atmospheres on some hot super-Earths. We argue that on close-orbiting tidally locked super-Earths, the tidal forces, together with the orbital and rotational centrifugal forces, can partially confine the atmosphere on the nightside. Assuming a super-terran body with an atmosphere dominated by volcanic species and a large hydrogen component, the heavier molecules can be shown to be confined within latitudes of ≲80° while the volatile hydrogen is not. Because of this disparity, the hydrogen has to slowly diffuse out into the dayside where X-ray and ultraviolet irradiation destroys it. For this mechanism to take effect, it is necessary for the exoplanet to become tidally locked before losing the totality of its hydrogen envelope. Consequently, for super-Earths with this proposed configuration, it is possible to solve the tidal-locking and mass-loss timescales in order to constrain their formation "birth" masses. Our model predicts that 55 Cancri e formed with a day length between approximately 17-18.5 hr and an initial mass less than ∼12M⊕, hence allowing it to become tidally locked before the complete destruction of its atmosphere. For comparison, CoRoT-7b, an exoplanet with very similar properties to 55 Cancri e but lacking an atmosphere, formed with a day length significantly different from ∼20.5 hr while also having an initial mass smaller than ∼9M⊕.

Keywords: super earths; exoplanet atmospheres; atmospheric circulation; near ultraviolet astronomy; solar ultraviolet emission; solar extreme ultraviolet emission; tidal interaction
Stellar Parameters and Spectroscopic Properties of TESS Objects Observed in the LAMOST Low- and Medium-resolution Spectral Survey

Stellar parameters and magnetic activity are important for the understanding of stellar physics and dynamo theory. We have used LAMOST spectroscopic surveys to study stellar parameters and magnetic activity properties of TESS objects. There are 46,684 spectra of 31,385 TESS objects in the LAMOST low-resolution spectral survey. We have calculated equivalent widths of Ca II H and K, and Hα lines, and discussed the relationship of chromospheric activity with stellar temperature. There are 25,710 spectra of 10,404 stars with repeated low-resolution observations. We found that there are 694 objects with variations of the Hα line and 1406 objects with varying radial velocities. Moreover, there are 14,099 spectra of 5834 TESS objects in the LAMOST medium-resolution survey, of which there are 2666 objects with Hα variations and 1480 objects with variation in radial velocities. By using the light curves of the TESS objects in the LAMOST field, we detected 4269 flare events and determined their flare parameters. We have confirmed that the fraction of the flare stars increases as stellar temperature decreases. There is also an observed relationship between the flare energy and chromospheric activity. We have calculated the power-law index between the flare energy and decay time using TESS data to be 0.27(0.01), which can be explained by the magnetic reconnection theory. We confirmed that ${R}_{{\rm{H}}\alpha }^{{\prime} }$ is stable for Rossby number R < 0.1 and decreases with the increase of Rossby number R > 0.1. There is a positive correlation between the brightness variation amplitude due to star spots from TESS and the Hα intensity from LAMOST.

Keywords: stellar activity; stellar chromospheres; stellar flares
Onboard Science Instrument Autonomy for the Detection of Microscopy Biosignatures on the Ocean Worlds Life Surveyor

The quest to find extraterrestrial life is a critical scientific endeavor with civilization-level implications. Icy moons in our solar system are promising targets for exploration because their liquid oceans make them potential habitats for microscopic life. However, the lack of a precise definition of life poses a fundamental challenge to formulating detection strategies. To increase the chances of unambiguous detection, a suite of complementary instruments must sample multiple independent biosignatures (e.g., composition, motility/behavior, and visible structure). Such an instrument suite could generate 10,000× more raw data than is possible to transmit from distant ocean worlds like Enceladus or Europa. To address this bandwidth limitation, Onboard Science Instrument Autonomy (OSIA) is an emerging discipline of flight systems capable of evaluating, summarizing, and prioritizing observational instrument data to maximize science return. We describe two OSIA implementations developed as part of the Ocean World Life Surveyor (OWLS) prototype instrument suite at the Jet Propulsion Laboratory. The first identifies life-like motion in digital holographic microscopy videos, and the second identifies cellular structure and composition via innate and dye-induced fluorescence. Flight-like requirements and computational constraints were used to lower barriers to infusion, similar to those available on the Mars helicopter, "Ingenuity." We evaluated the OSIA's performance using simulated and laboratory data and conducted a live field test at the hypersaline Mono Lake planetary analog site. Our study demonstrates the potential of OSIA for enabling biosignature detection and provides insights and lessons learned for future mission concepts aimed at exploring the outer solar system.

Keywords: biosignatures; astrobiology; saturnian satellites; galilean satellites; ocean planets
Simple Physics and Integrators Accurately Reproduce Mercury Instability Statistics

The long-term stability of the solar system is an issue of significant scientific and philosophical interest. The mechanism leading to instability is Mercury's eccentricity being pumped up so high that Mercury either collides with Venus or is scattered into the Sun. Previously, only three five-billion-year N-body ensembles of the solar system with thousands of simulations have been run to assess long-term stability. We generate two additional ensembles, each with 2750 members, and make them publicly available at https://archive.org/details/@dorianabbot. We find that accurate Mercury instability statistics can be obtained by (1) including only the Sun and the eight planets, (2) using a simple Wisdom-Holman scheme without correctors, (3) using a basic representation of general relativity, and (4) using a time step of 3.16 days. By combining our solar system ensembles with previous ensembles, we form a 9601-member ensemble of ensembles. In this ensemble of ensembles, the logarithm of the frequency of a Mercury instability event increases linearly with time between 1.3 and 5 Gyr, suggesting that a single mechanism is responsible for Mercury instabilities in this time range and that this mechanism becomes more active as time progresses. Our work provides a robust estimate of Mercury instability statistics over the next five billion years, outlines methodologies that may be useful for exoplanet system investigations, and provides two large ensembles of publicly available solar system integrations that can serve as test beds for theoretical ideas as well as training sets for artificial intelligence schemes.

Keywords: solar system; mercury (planet); planetary dynamics
Streaming Instabilities in Accreting and Magnetized Laminar Protoplanetary Disks

The streaming instability (SI) is one of the most promising pathways to the formation of planetesimals from pebbles. Understanding how this instability operates under realistic conditions expected in protoplanetary disks (PPDs) is therefore crucial to assess the efficiency of planet formation. Contemporary models of PPDs show that magnetic fields are key to driving gas accretion through large-scale, laminar magnetic stresses. However, the effect of such magnetic fields on the SI has not been examined in detail. To this end, we study the stability of dusty, magneftized gas in a protoplanetary disk. We find the SI can be enhanced by passive magnetic torques and even persist in the absence of a global radial pressure gradient. In this case, instability is attributed to the azimuthal drift between dust and gas, unlike the classical SI, which is driven by radial drift. This suggests that the SI can remain effective inside dust-trapping pressure bumps in accreting disks. When a live vertical field is considered, we find the magneto-rotational instability can be damped by dust feedback, while the classic SI can be stabilized by magnetic perturbations. We also find that Alfvén waves can be destabilized by dust-gas drift, but this instability requires nearly ideal conditions. We discuss the possible implications of these results for dust dynamics and planetesimal formation in PPDs.

Keywords: protoplanetary disks; hydrodynamics; planet formation; astrophysical fluid dynamics; magnetohydrodynamics
Molecular Dynamics Approach for Predicting Release Temperatures of Noble Gases in Presolar Nanodiamonds

Presolar meteoritic nanodiamond grains carry an array of isotopically distinct noble gas components and provide information on the history of nucleosynthesis, galactic mixing, and the formation of the solar system. In this paper, we develop a molecular dynamics approach to predict the thermal release pattern of implanted noble gases (He and Xe) in nanodiamonds. We provide atomistic details of the unimodal temperature release distribution for He and a bimodal behavior for Xe. Intriguingly, our model shows that the thermal release process of noble gases is highly sensitive to the impact and annealing parameters, as well as the position of the implanted ion in the crystal lattice and morphology of the nanograin. In addition, the model elegantly explains the unimodal and bimodal patterns of noble gas release via the interstitial and substitutional types of defects formed. In summary, our simulations confirm that low-energy ion implantation is a viable way to incorporate noble gases into nanodiamonds, and we provide an explanation of the experimentally observed peculiarities of gas release.

Keywords: meteorites; n-body simulations