adsabs/SciX_UAT_keywords huggingface dataset:
Shell-type Tidal Features Are More Frequently Detected in Slowly Rotating Early-type Galaxies than Stream- and Tail-type Features

To enhance our understanding of the impact of galaxy mergers on the kinematics of early-type galaxies (ETGs), we examine differences in specific stellar angular momentum within the half-light radius ( ${\lambda }_{{R}_{e}}$ ) among ETGs with different types of tidal features and those without such features. This is accomplished by categorizing tidal features, which serve as direct evidence of recent mergers, into shells, streams, and tails, through deep images from the DESI Legacy Survey, and by using MaNGA data for the analysis of the kinematics of 1244 ETGs at z < 0.055. We find that ETGs with tidal features typically have reduced ${\lambda }_{{R}_{e}}$ values that are lower by 0.12 dex than ETGs without tidal features. ETGs with shells contribute most to the reduction in ${\lambda }_{{R}_{e}}$ . Consequently, nearly half of ETGs with shells are classified as slow rotators, a fraction that is more than twice as high as that of ETGs with tails or streams, and over three times higher than that of ETGs without tidal features. These trends generally remain valid even when ETGs are divided into several mass bins. Our findings support the idea that radial mergers, which are more effective at reducing ${\lambda }_{{R}_{e}}$ than circular mergers, are more closely associated with the formation of shells rather than streams or tails. The detection of shells in slightly more massive ETGs compared to streams and tails may be attributed to the fact that massive satellite galaxies are more likely to be accreted through radial orbits, due to the nature of dynamical friction.

Keywords: early-type galaxies; galaxy kinematics; galaxy mergers; galaxy properties; tidal tails; galaxy rotation
Mirror and Proton-cyclotron Instabilities Coexisting with Ambient Turbulence in a Proton-Alpha Plasma

We investigate the effect of ambient turbulence on the mirror and proton-cyclotron instabilities in a proton-alpha particle plasma. We perform three-dimensional hybrid simulations with particle-in-cell ions and a quasi-neutralizing electron fluid. The instabilities are driven by the protons with temperature perpendicular to the mean magnetic field larger than the parallel temperature. The description of these instabilities is usually based on the assumption of a uniform and stationary background. However, this assumption is violated by the ambient turbulence. In particular, the turbulent fluctuations modify the particle distribution function by making it spatially inhomogeneous and time-dependent. We compare the properties of the instabilities to the case of a uniform and stationary background and the same average temperature anisotropy and plasma beta. We find that the initial growth rates of the mirror mode are close, but the saturation level is significantly reduced when the turbulence is present. The saturation level of the proton-cyclotron mode is not affected as strongly.

Keywords: solar wind; interplanetary turbulence; space plasmas
GRB 171205A: Hypernova and Newborn Neutron Star

GRB 171205A is a low-luminosity, long-duration gamma-ray burst (GRB) associated with SN 2017iuk, a broad-line type Ic supernova (SN). It is consistent with having been formed in the core collapse of a widely separated binary, which we have called the binary-driven hypernova of type III. The core collapse of the CO star forms a newborn NS (νNS) and the SN explosion. Fallback accretion transfers mass and angular momentum to the νNS, here assumed to be born non-rotating. The accretion energy injected into the expanding stellar layers powers the prompt emission. The multiwavelength power-law afterglow is explained by the synchrotron radiation of electrons in the SN ejecta, powered by energy injected by the spinning νNS. We calculate the amount of mass and angular momentum gained by the νNS, as well as the νNS rotational evolution. The νNS spins up to a period of 47 ms, then releases its rotational energy powering the synchrotron emission of the afterglow. The paucity of the νNS spin explains the low-luminosity characteristic and that the optical emission of the SN from the nickel radioactive decay outshines the optical emission from the synchrotron radiation. From the νNS evolution, we infer that the SN explosion had to occur at most 7.36 h before the GRB trigger. Therefore, for the first time, the analysis of the GRB data leads to the time of occurrence of the CO core collapse leading to the SN explosion and the electromagnetic emission of the GRB event.

Keywords: gamma-ray bursts; neutron stars; pulsars
Mass Transfer Theory Based Analysis of Influencing Factors on Component Gradient of Near-surface Atmosphere on Venus

The atmosphere of Venus differs completely from that of Earth despite the planets' similarity in size and mass. At Venus's surface, the atmosphere is hot and dense, with a temperature of approximately 735 K and a pressure of approximately 92 bar. The temperature profile from the Soviet VeGa-2 probe shows high instability of the near-ground potential temperature, which, according to relevant research, can be explained by the vertical gradient of N2 mole fraction. Based on the Maxwell-Stefan mass transfer theory, we propose a theoretical model of binary gas component for a quantitative discussion of influencing factors for the N2 vertical concentration gradient, which consist of temperature, gravity, specific heat ratio, mass relative factor, thermal diffusion factor, and CO2 flux. Our model shows that the 0%-3.5% N2 concentration gradient cannot be generated without CO2 flux in the near-ground atmosphere of Venus. And the result with CO2 source indicates that the 0.000001%-3.5% N2 concentration gradient at 0-7 km atmosphere can be generated by the 2.7 × 10-6 mol m-2 s-6 CO2 flux on Venusian surface, which is in agreement of gradient reckoned by VeGa-2's data. This magnitude of CO2 flux is close to the one produced by volcanic eruptions on Earth, indicating possible existence of volcanic activities on the surface of Venus. This work has provided the community a new vision to understand the influencing factors of Venusian atmospheres composition distribution.

Keywords: solar system terrestrial planets; venus; solar system; atmospheric composition; planetary atmospheres
Elemental Abundances of the Super-Neptune WASP-107b's Host Star Using High-resolution, Near-infrared Spectroscopy

We present the first elemental abundance measurements of the K dwarf (K7V) exoplanet-host star WASP-107 using high-resolution (R ≃45,000), near-infrared (H- and K-band) spectra taken from Gemini-S/IGRINS. We use the previously determined physical parameters of the star from the literature and infer the abundances of 15 elements—C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni, all with precision < 0.1 dex—based on model fitting using MARCS model atmospheres and the Turbospectrum spectral synthesis code. Our results show near-solar abundances and a carbon-to-oxygen ratio (C/O) of 0.50 ± 0.10, which is consistent with the solar value of 0.54 ± 0.09. The orbiting planet, WASP-107b, is a super-Neptune with a mass in the Neptune regime (=1.8 M Nep) and a radius close to Jupiter's (=0.94 R Jup). This planet is also being targeted by four JWST Cycle 1 programs in transit and eclipse, which should provide highly precise measurements of atmospheric abundances. This will enable us to properly compare the planetary and stellar chemical abundances, which is essential in understanding the formation mechanisms, internal structure, and chemical composition of exoplanets. Our study is a proof-of-concept that will pave the way for such measurements to be made for all of JWST's cooler exoplanet-host stars.

Keywords: k dwarf stars
Implementation of Chemistry in the Athena++ Code

Chemistry plays a key role in many aspects of astrophysical fluids. Atoms and molecules are agents for heating and cooling, determine the ionization fraction, serve as observational tracers, and build the molecular foundation of life. We present the implementation of a chemistry module in the publicly available magnetohydrodynamic code Athena++. We implement several chemical networks and heating and cooling processes suitable for simulating the interstellar medium (ISM). A general chemical network framework in the KIDA format is also included, allowing users to easily implement their own chemistry. Radiation transfer and cosmic-ray ionization are coupled with chemistry and solved with the simple six-ray approximation. The chemical and thermal processes are evolved as a system of coupled ordinary differential equations with an implicit solver from the CVODE library. We perform and present a series of tests to ensure the numerical accuracy and convergence of the code. Many tests combine chemistry with gas dynamics, including comparisons with analytic solutions, 1D problems of the photodissociation regions and shocks, and realistic 3D simulations of the turbulent ISM. We release the code with the new public version of Athena++, aiming to provide a robust and flexible code for the astrochemical simulation community.

Keywords: astrochemistry; magnetohydrodynamical simulations; interstellar medium
Electrostatic Repulsion of Dust from Planetary Surfaces

Surfaces of planetary bodies can have strong electric fields, subjecting conductive grains to repulsive electrostatic forces. This has been proposed as a mechanism to eject grains from the ground. To quantify this process, we study millimeter-sized basalt aggregates consisting of micrometer constituents exposed to an electric field in drop-tower experiments. The dust aggregates acquire high charges on subsecond timescales while sticking to the electrodes according to the field polarity. Charging at the electrodes results in a repulsive (lifting) force and continues until repulsion overcomes adhesion and particles are lifted, moving toward the opposite electrode. Some aggregates remain attached, which is consistent with a maximum charge limit being reached, providing an electrostatic force too small to counteract adhesion. All observations are in agreement with a model of moderately conductive grains with a small but varying number of adhesive contacts to the electrodes. This supports the idea that on planetary surfaces with atmospheres, electrostatic repulsion can significantly contribute to airborne dust and sand, i.e., decrease the threshold wind speed that is required for saltation and increase the particle flux as suggested before.

Keywords: dust physics; charge transfer; atmospheric dynamics; planetary surfaces; surface processes
Potential Melting of Extrasolar Planets by Tidal Dissipation

Tidal heating on Io due to its finite eccentricity was predicted to drive surface volcanic activity, which was subsequently confirmed by the Voyager spacecraft. Although the volcanic activity in Io is more complex, in theory volcanism can be driven by runaway melting in which the tidal heating increases as the mantle thickness decreases. We show that this runaway melting mechanism is generic for a composite planetary body with liquid core and solid mantle, provided that (i) the mantle rigidity, μ, is comparable to the central pressure, i.e., μ/(ρ gR P) ≳ 0.1 for a body with density ρ, surface gravitational acceleration g, and radius R P; (ii) the surface is not molten; (iii) tides deposit sufficient energy; and (iv) the planet has nonzero eccentricity. We calculate the approximate liquid core radius as a function of μ/(ρ gR P), and find that more than 90% of the core will melt due to this runaway for μ/(ρ gR P) ≳ 1. From all currently confirmed exoplanets, we find that the terrestrial planets in the L 98-59 system are the most promising candidates for sustaining active volcanism. However, uncertainties regarding the quality factors and the details of tidal heating and cooling mechanisms prohibit definitive claims of volcanism on any of these planets. We generate synthetic transmission spectra of these planets assuming Venus-like atmospheric compositions with an additional 5%, 50%, and 98% SO2 component, which is a tracer of volcanic activity. We find a ≳3σ preference for a model with SO2 with 5-10 transits with JWST for L 98-59bcd.

Keywords: volcanism; exoplanet tides; tides
Measuring the Total Ultraviolet Light from Galaxy Clusters at z = 0.5-1.6: The Balance of Obscured and Unobscured Star Formation

Combined observations from UV to IR wavelengths are necessary to fully account for the star formation in galaxy clusters. Low-mass galaxies with ${\rm{log}}({M}_{\ast }/{M}_{\odot })\lt 10$ are typically not individually detected, particularly at higher redshifts (z ~ 1-2) where galaxy clusters are undergoing rapid transitions from hosting mostly active, dust-obscured star-forming galaxies to hosting quiescent, passive galaxies. To account for these undetected galaxies, we measure the total light emerging from GALEX/near-UV stacks of galaxy clusters at z = 0.5-1.6. Combined with existing measurements from Spitzer, WISE, and Herschel, we study the average UV through far-IR spectral energy distribution (SED) of clusters. From the SEDs, we measure the total stellar mass and amount of dust-obscured and unobscured star formation arising from all cluster-member galaxies, including the low-mass population. The relative fraction of unobscured star formation we observe in the UV is consistent with what is observed in field galaxies. There is tentative evidence for lower than expected unobscured star formation at z ~ 0.5, which may arise from rapid redshift evolution in the low-mass quenching efficiency in clusters reported by other studies. Finally, the GALEX data place strong constraints on derived stellar-to-halo mass ratios at z < 1, which anticorrelate with the total halo mass, consistent with trends found from local X-ray observations of clusters. The data exhibit steeper slopes than implementations of the cluster star formation efficiency in semianalytical models.

Keywords: galaxy evolution; high-redshift galaxy clusters; galaxy clusters; star formation
The Variation of the Solar Wind Correlation Scale and Taylor Scale Upstream of Mars Observed by MAVEN

The correlation scale and Taylor scale, which characterize the turbulence and dissipation levels, of the solar wind upstream of Mars are determined using the Mars atmosphere and volatile evolution magnetic field data from 2015 to 2020, which covers half of a solar cycle from the solar maximum to the solar minimum. Our analysis suggests that the correlation scale varies between 10 and 20 hr and the Taylor scale between 0.3 and 1 s. Applying the frozen-in flow approximation, we convert the two temporal scales to the two spatial scales, which are about (1.5-3.0) × 107 km and 150-500 km, respectively. We further compare the correlation scale and Taylor scale to the sunspot number (SSN) to study the impacts of solar activity. The highest correlation coefficient between the correlation scale and the SSN is 0.78, where the two data sets are shifted by 16 months with the correlation scale behind the SSN. For the Taylor scale, the highest correlation coefficient is 0.52 with the time lag of 17 months. We also analyze the effective magnetic Reynolds number that is the square of the ratio of the two scales. It is more than 3 × 109, suggesting the good assumption of the frozen-in flow. However, its correlation with the SSN is weak.

Keywords: solar wind; mars; interplanetary magnetic fields; solar activity; interplanetary turbulence
An Unusual Pulse Shape Change Event in PSR J1713+0747 Observed with the Green Bank Telescope and CHIME

The millisecond pulsar J1713+0747 underwent a sudden and significant pulse shape change between 2021 April 16 and 17 (MJDs 59320 and 59321). Subsequently, the pulse shape gradually recovered over the course of several months. We report the results of continued multifrequency radio observations of the pulsar made using the Canadian Hydrogen Intensity Mapping Experiment and the 100 m Green Bank Telescope in a 3 yr period encompassing the shape change event, between 2020 February and 2023 February. As of 2023 February, the pulse shape had returned to a state similar to that seen before the event, but with measurable changes remaining. The amplitude of the shape change and the accompanying time-of-arrival residuals display a strong nonmonotonic dependence on radio frequency, demonstrating that the event is neither a glitch (the effects of which should be independent of radio frequency, ν) nor a change in dispersion measure alone (which would produce a delay proportional to ν ‑2). However, it does bear some resemblance to the two previous "chromatic timing events" observed in J1713+0747, as well as to a similar event observed in PSR J1643‑1224 in 2015.

Keywords: pulsars; millisecond pulsars; radio astrometry
Abundant Atmospheric Methane from Volcanism on Terrestrial Planets Is Unlikely and Strengthens the Case for Methane as a Biosignature

The disequilibrium combination of abundant methane and carbon dioxide has been proposed as a promising exoplanet biosignature that is readily detectable with upcoming telescopes such as the James Webb Space Telescope. However, few studies have explored the possibility of nonbiological CH4 and CO2 and related contextual clues. Here we investigate whether magmatic volcanic outgassing on terrestrial planets can produce atmospheric CH4 and CO2 with a thermodynamic model. Our model suggests that volcanoes are unlikely to produce CH4 fluxes comparable to biological fluxes. Improbable cases where volcanoes produce biological amounts of CH4 also produce ample carbon monoxide. We show, using a photochemical model, that high abiotic CH4 abundances produced by volcanoes would be accompanied by high CO abundances, which could be a detectable false-positive diagnostic. Overall, when considering known mechanisms for generating abiotic CH4 on terrestrial planets, we conclude that observations of atmospheric CH4 with CO2 are difficult to explain without the presence of biology when the CH4 abundance implies a surface flux comparable to modern Earth's biological CH4 flux. A small or negligible CO abundance strengthens the CH4+CO2 biosignature because life readily consumes atmospheric CO, while reducing volcanic gases likely cause CO to build up in a planet's atmosphere. Furthermore, the difficulty of volcanically generated CH4-rich atmospheres suitable for an origin of life may favor alternatives such as impact-induced reducing atmospheres.

Keywords: biosignatures; astrobiology; planetary atmospheres; volcanoes
The First Ultracompact Roche Lobe-Filling Hot Subdwarf Binary

We report the discovery of the first short-period binary in which a hot subdwarf star (sdOB) filled its Roche lobe and started mass transfer to its companion. The object was discovered as part of a dedicated high-cadence survey of the Galactic plane named the Zwicky Transient Facility and exhibits a period of P = 39.3401(1) minutes, making it the most compact hot subdwarf binary currently known. Spectroscopic observations are consistent with an intermediate He-sdOB star with an effective temperature of T_{eff} = 42,400 ± 300 K and a surface gravity of log (g) = 5.77 ± 0.05. A high signal-to-noise ratio GTC+HiPERCAM light curve is dominated by the ellipsoidal deformation of the sdOB star and an eclipse of the sdOB by an accretion disk. We infer a low-mass hot subdwarf donor with a mass MsdOB = 0.337 ± 0.015 M_{⊙} and a white dwarf accretor with a mass MWD = 0.545 ± 0.020 M_{⊙}. Theoretical binary modeling indicates the hot subdwarf formed during a common envelope phase when a 2.5-2.8 M_{⊙} star lost its envelope when crossing the Hertzsprung gap. To match its current P_{orb}, T_{eff}, log (g), and masses, we estimate a post-common envelope period of P_{orb} ≈ 150 minutes and find that the sdOB star is currently undergoing hydrogen shell burning. We estimate that the hot subdwarf will become a white dwarf with a thick helium layer of ≈0.1 M_{⊙}, merge with its carbon/oxygen white dwarf companion after ≈17 Myr, and presumably explode as a thermonuclear supernova or form an R CrB star.

Keywords: b subdwarf stars; stellar evolution; compact binary stars; white dwarf stars
Advancing Precision Particle Background Estimation for Future X-Ray Missions: Correlated Variability between the Alpha Magnetic Spectrometer and Chandra/XMM-Newton

Galactic cosmic-ray (GCR) particles have a significant impact on the particle-induced background of X-ray observatories, and their flux exhibits substantial temporal variability, potentially influencing background levels. In this study, we present 1 day binned high-energy reject rates derived from the Chandra-ACIS and XMM-Newton EPIC-pn instruments, serving as proxies for the GCR particle flux. We systematically analyze the ACIS and EPIC-pn reject rates and compare them with the AMS proton flux. Our analysis initially reveals robust correlations between the AMS proton flux and the ACIS/EPIC-pn reject rates when binned over 27 day intervals. However, a closer examination reveals substantial fluctuations within each 27 day bin, indicating shorter-term variability. Upon daily binning, we observe finer temporal structures in the data sets, demonstrating the presence of recurrent variations with periods of ∼25 days and 23 days in the ACIS and EPIC-pn reject rates, respectively, spanning the years 2014–2018. Notably, during the 2016–2017 period, we additionally detect periodicities of ∼13.5 days and 9 days in the ACIS and EPIC-pn reject rates, respectively. Intriguingly, we observe a time lag of ∼6 days between the AMS proton flux and the ACIS/EPIC-pn reject rates during the second half of 2016. This time lag is not visible before 2016 and after 2017. The underlying physical mechanisms responsible for this time lag remain a subject of ongoing investigation.

Keywords: galactic cosmic rays
Energy Conversion during Asymmetric Magnetic Reconnection

Asymmetric magnetic reconnection usually occurs at the Earth's magnetopause, where the magnetic field strength and plasma density are different between the magnetosheath and magnetosphere. In this paper, a two-dimensional particle-in-cell simulation model is used to study the energy conversion during asymmetric magnetic reconnection. Energy conversion can occur in the vicinity of the X-line, magnetosphere separatrix region, and reconnection fronts. In the vicinity of the X-line and magnetosphere separatrix region, the electromagnetic field energy is mainly transferred to electrons, while at the reconnection fronts, the electromagnetic field energy is mainly transferred to ions. For the case with weak magnetic field asymmetry, the reconnection fronts dominate the energy conversion, which is related to the inflowing Poynting flux S z at the fronts. For the case with strong magnetic field asymmetry, the energy conversion occurs around the X-line and magnetosphere separatrix region, but no longer at the reconnection fronts. This is because the inflowing Poynting flux S x near the magnetosphere separatrices provides electromagnetic energy for energy conversion. The density asymmetry has no significant effect on the spatial distribution of the energy conversion.

Keywords: plasma physics; magnetic fields