adsabs/SciX_UAT_keywords huggingface dataset:
Mapping Circumstellar Magnetic Fields of Late-type Evolved Stars with the Goldreich-Kylafis Effect: CARMA Observations at λ1.3 mm of R Crt and R Leo

Mapping magnetic fields is the key to resolving the unclear physical picture of circumstellar magnetic fields in late-type evolved stars. Observations of linearly polarized emission from thermal molecular line transitions due to the Goldreich-Kylafis (G-K) effect provide valuable insights into the magnetic field geometry in these sources that are complementary to other key studies. In this paper, we present the detection of spectral-line polarization from both the thermal J = 2-1 CO line and the v = 1, J = 5-4 SiO maser line toward two thermal-pulsating asymptotic giant branch stars, R Crt and R Leo. The observed fractional linear polarization in the CO emission is measured as ml ∼ 3.1% and ml ∼ 9.7% for R Crt and R Leo, respectively. A circumstellar envelope (CSE) model profile and the associated parameters are estimated and used as input to a more detailed modeling of the predicted linear polarization expected from the G-K effect. The observed thermal line polarization level is consistent with the predicted results from the G-K model for R Crt; additional effects need to be considered for R Leo.

Keywords: asymptotic giant branch stars; polarimetry; stellar magnetic fields; co line emission; circumstellar masers
CLASS Observations of Atmospheric Cloud Polarization at millimeter Wavelengths

The dynamic atmosphere imposes challenges to ground-based cosmic microwave background observation, especially for measurements on large angular scales. The hydrometeors in the atmosphere, mostly in the form of clouds, scatter the ambient thermal radiation and are known to be the main linearly polarized source in the atmosphere. This scattering-induced polarization is significantly enhanced for ice clouds due to the alignment of ice crystals under gravity, which are also the most common clouds seen at the millimeter-astronomy sites at high altitudes. This work presents a multifrequency study of cloud polarization observed by the Cosmology Large Angular Scale Surveyor experiment on Cerro Toco in the Atacama Desert of northern Chile, from 2016-2022, at the frequency bands centered around 40, 90, 150, and 220 GHz. Using a machine-learning-assisted cloud classifier, we made connections between the transient polarized emission found in all four frequencies with the clouds imaged by monitoring cameras at the observing site. The polarization angles of the cloud events are found to be mostly 90° from the local meridian, which is consistent with the presence of horizontally aligned ice crystals. The 90 and 150 GHz polarization data are consistent with a power law with a spectral index of 3.90 ± 0.06, while an excess/deficit of polarization amplitude is found at 40/220 GHz compared with a Rayleigh scattering spectrum. These results are consistent with Rayleigh-scattering-dominated cloud polarization, with possible effects from supercooled water absorption and/or Mie scattering from a population of large cloud particles that contribute to the 220 GHz polarization.

Keywords: earth's clouds; polarimetry; cosmic microwave background radiation
SpuBase: Solar Wind Ion Sputter Database for Modeling Purposes

We supply the modelers with a database, SpuBase (doi:10.5281/zenodo.10783295), that is based on the latest approach for obtaining solar wind ion sputter yields in agreement with experimental sputter data outlined in Jäggi et al. We include an overview of sputter results for typical Lunar and Hermean surfaces. To obtain total sputter yields for any given surface, we perform a mass balance of individual mineral sputter yields. For a set of impact angles, the angular and energy distribution data are scaled according to the sputter yield, summed up and fitted to obtain one probability distribution for each chemical element involved. Comparison of the results from different geochemical terranes on the Moon and Mercury has shown that variations in the abundance of silicates result in comparable energy and angular distribution data owing to the underlying model assumptions. The inclusion of sulfides relevant for Mercury, however, significantly affects the energy and angular distributions of sputtered particles. The application of the damage-driven sulfur diffusion rate in FeS in all sulfur-bearing minerals results in 35 times lower sulfur yields on average and a less prominent forward sputtering of sulfur at grazing incidence angles.

Keywords: solar wind; exosphere; mercury (planet); the moon; asteroids
Presolar Silicate and Oxide Grains Found in Lithic Clasts from Isheyevo and the Fine-grained Matrix of Northwest Africa 801

We report on the discovery of 33 oxygen-anomalous grains from the CH3/CBb3 chondrite Isheyevo and the CR2 chondrite Northwest Africa (NWA) 801. Oxygen isotopic compositions indicate the origin of the majority grains in stellar outflows of low-mass (∼1.2 to ∼2.2 M⊙), solar-metallicity red giant or asymptotic giant branch stars, while highly 17O-enriched grains probably have nova origins. Isotopic compositions of the eight 18O-rich grains, including an extremely 18O-rich grain (∼16 times solar 18O/16O ratio), are reproduced by zone mixing of SNe II ejecta. Close-to-normal silicon, magnesium, and calcium isotopic compositions of grains are consistent with the isotope exchange in the interstellar medium or the meteorite parent body, while two grains with Si isotopic anomalies and one grain with Mg isotopic anomalies reflect the Galactic chemical evolution. An Isheyevo clast showed several hot spots with moderate to high 15N enrichments, including a hot spot with an extreme 15N excess of (7225 ± 316)‰. However, no correlation between 15N enrichment and presolar oxygen-rich grain abundance is found. Grains with elliptical shapes probably indicate primary condensation feature. Two complex grains possibly display decoupling of the isotopic and elemental compositions in the grain formation environments. The low silicate-to-oxide abundance ratio for the fine-grained chondrule rims in NWA 801 likely reflects the preferential destruction of silicates due to terrestrial weathering. In NWA 801, the presolar O-rich grain abundance in fine-grained chondrule rims is higher than in the interchondrule matrix, similar to the trend observed for some aqueously altered chondrites of petrologic type 2.

Keywords: meteorites; carbonaceous chondrites; circumstellar dust; asymptotic giant branch stars; type ii supernovae; silicate grains; novae
Gravitational-wave Capture in Spinning Black Hole Encounters

The orbits of two black holes (BHs) that are initially unbound can be transformed into bound orbits by emitting gravitational waves during close encounters in a star cluster, which is called gravitational-wave (GW) capture. The effects of spin of BHs on GW capture are investigated in the context of numerical relativity. The radiated energy during the encounter is dependent on the effective spin when the BHs have equal masses, as expected from post-Newtonian approximation. The strongest emission is produced when the spins of both BHs are anti-aligned to the orbital angular momentum in the case of fly-by encounters. But the opposite is true in the case of direct merging: the strongest emission comes from the BHs with aligned spins to the orbital angular momentum. The fraction of direct merging among the GW captures increases in proportion to v4/7, assuming the uniform distribution of pericenter distances in the encounters, where v is the velocity dispersion of the cluster, which means about 5% of GW capture leads to the direct merging for star clusters with v = 150 km s-1.

Keywords: general relativity; two-body problem; rotating black holes
Evidence for Asteroid Scattering and Distal Solar System Solids From Meteorite Paleomagnetism

Asteroid-sized bodies are predicted to have been scattered throughout the solar system following gravitational interactions with the giant planets. This process could have delivered water-rich small bodies to the inner solar system. However, evidence from the meteorite record supporting this scattering is limited due to difficulties in recovering the formation distance of meteorite parent bodies from laboratory measurements. Moreover, ancient millimeter-sized solids that formed in the inner solar system (calcium-aluminum-rich inclusions (CAIs) and chondrules) have also been proposed to have migrated throughout the solar system, which could have been key to their survival. Our understanding of the driving mechanisms, distances, and timings involved in this motion is also restricted for the same reasons. Here, we address these limitations by recovering the formation distance of the parent asteroid of the Tagish Lake meteorite from measurements of its natural remanent magnetization. We find that this meteorite experienced an ancient field intensity <0.15 μT. Accounting for the average effect of a tilted parent body rotation axis and possible uncertainties associated with the remanence acquisition mechanism, this result argues that the Tagish Lake parent body formed at >8-13 au, suggesting this body originates from the distal solar system. Tagish Lake came to Earth from the asteroid belt which, combined with our recovered formation distance, suggests that some small bodies traveled large distances throughout the solar system. Moreover, Tagish Lake contains CAIs and chondrules, indicating that these solids were capable of traveling to the distal solar system within just a few million years.

Keywords: meteorites; magnetic fields; primordial magnetic fields; asteroid belt; asteroids; kuiper belt; protoplanetary disks; chondrites; chondrules; carbonaceous chondrites
Potential Signature of Population III Pair-instability Supernova Ejecta in the BLR Gas of the Most Distant Quasar at z = 7.54

The search for Population III stars has fascinated and eluded astrophysicists for decades. One promising place for capturing evidence of their presence must be high-redshift objects; signatures should be recorded in their characteristic chemical abundances. We deduce the Fe and Mg abundances of the broadline region (BLR) from the intensities of ultraviolet Mg II and Fe II emission lines in the near-infrared spectrum of UKIDSS Large Area Survey (ULAS) J1342+0928 at z = 7.54, by advancing our novel flux-to-abundance conversion method developed for quasars up to z ~ 3. We find that the BLR of this quasar is extremely enriched, by a factor of 20 relative to the solar Fe abundance, together with a very low Mg/Fe abundance ratio: [Fe/H] = +1.36 ± 0.19 and [Mg/Fe] =-1.11 ± 0.12, only 700 million years after the Big Bang. We conclude that such an unusual abundance feature cannot be explained by the standard view of chemical evolution that considers only the contributions from canonical supernovae. While there remains uncertainty in the high-mass end of the Population III initial mass function, here we propose that the larger amount of iron in ULAS J1342+0928 was supplied by a pair-instability supernova (PISN) caused by the explosion of a massive Population III star in the high-mass end of the possible range of 150-300 M ⊙ . Chemical evolution models based on initial PISN enrichment well explain the trend in [Mg/Fe]-z all the way from z < 3 to z = 7.54. We predict that stars with very low [Mg/Fe] at all metallicities are hidden in the galaxy, and they will be efficiently discovered by ongoing new-generation photometric surveys. *At the time of writing this paper, the highest redshift record has been updated to z = 7.642, ULAS J0313-1806, as reported by Wang et al. ().

Keywords: quasars; chemical abundances; population iii stars; nucleosynthesis
Curious Changes in Association of Complex Sunspot Groups with X-Ray Flares (≥M1) in Solar Cycles 22-24

We investigate the variations in the probabilities of complex sunspot groups (SGs)—large, asymmetric, or δ-type SGs—producing X-ray flares (≥M1) in solar cycles (SCs) 22, 23, and 24 based on the SG data collected by the United States Air Force/Mount Wilson Observatory and the flare data recorded by Geostationary Operational Environmental Satellites. The following are the main findings. (1) For complex SGs in the whole disk as well as the northern and southern hemispheres during SC 22, their numbers and probabilities of producing flares change almost synchronously. (2) For complex SGs during SC 23, probabilities of producing flares during the early declining phase in the whole disk do not decrease with decreasing complex SG number; in the northern hemisphere, the probability of producing flares during the declining phase is significantly higher than that during the maximum phase; in the southern hemisphere, there is no definite variation trend in the probabilities of producing flares during the maximum and declining phases. (3) For complex SGs during SC 24, the probabilities of producing flares during the later rising and early declining phases are significantly higher than or comparable to those during the maximum phase no matter how their numbers change; in the northern hemisphere, the probability of producing flares during the rising phase is significantly higher than or at least comparable to that during the maximum phase; in the southern hemisphere, there is no definite variation trend in the probabilities of producing flares during the maximum and declining phases.

Keywords: solar cycle; sunspot groups; solar x-ray flares
The Influence of Surface Binding Energy on Sputtering in Models of the Sodium Exosphere of Mercury

We have simulated the sodium (Na) exosphere of Mercury to show how the exosphere is affected by the assumed surface binding energy (SBE) of Na in the sputtered component. We constrained ion precipitation onto the surface using distributions for the cusp regions that are consistent with measurements by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging Fast Imaging Plasma Spectrometer instrument. We have simulated sputtering with SBEs of 0.27, 2.6, 4.4, and 7.9 eV, with the lowest value commonly used in exosphere models and the highest from recent molecular dynamics calculations for the Na-bearing feldspar end-member, albite. A gradual change in the exosphere is seen as the yield decreases and the ejecta energy increases with increasing SBE. We describe the corresponding exosphere source functions for ion sputtering (IS), as well as for the previously studied processes of micrometeoroid impact vaporization and photon-stimulated desorption (PSD), along with their release energy distributions and spatial distributions. We have summed the contributions of the various source processes to explain how and when the different sources can be distinguished by observations. The modeled exosphere scale heights range from 72 km for PSD to over 1000 km for IS using a SBE of 7.9 eV. We find that the processes responsible for generating Mercury's Na exosphere are separable by measuring line-of-sight column densities tangent to the planet at various altitudes and positions around the planet. Our initial results are consistent with the Na being sputtered from a high-SBE material such as feldspar, which has been predicted to be abundant on the Mercury's surface.

Keywords: mercury (planet); exosphere
SWASTi-CME: A Physics-based Model to Study Coronal Mass Ejection Evolution and Its Interaction with Solar Wind

Coronal mass ejections (CMEs) are primary drivers of space weather, and studying their evolution in the inner heliosphere is vital to prepare for a timely response. Solar wind streams, acting as background, influence their propagation in the heliosphere and associated geomagnetic storm activity. This study introduces SWASTi-CME, a newly developed MHD-based CME model integrated into the Space Weather Adaptive SimulaTion (SWASTi) framework. It incorporates a nonmagnetized elliptic cone and a magnetized flux rope CME model. To validate the model's performance with in situ observation at L1, two Carrington rotations were chosen: one during solar maxima with multiple CMEs, and one during solar minima with a single CME. The study also presents a quantitative analysis of CME-solar wind interaction using this model. To account for ambient solar wind effects, two scenarios of different complexity in solar wind conditions were established. The results indicate that ambient conditions can significantly impact some of the CME properties in the inner heliosphere. We found that the drag force on the CME front exhibits a variable nature, resulting in asymmetric deformation of the CME leading edge. Additionally, the study reveals that the impact on the distribution of CME internal pressure primarily occurs during the initial stage, while the CME density distribution is affected throughout its propagation. Moreover, regardless of the ambient conditions, it was observed that, after a certain propagation time (t), the CME volume follows a nonfractal power-law expansion (∝t 3.03-3.33) due to the attainment of a balanced state with ambient.

Keywords: solar coronal mass ejections; solar wind; magnetohydrodynamical simulations
Early Planet Formation in Embedded Disks (eDisk). X. Compact Disks, Extended Infall, and a Fossil Outburst in the Class I Oph IRS43 Binary

We present the first results from the Early Planet Formation in Embedded Disks Atacama Large Millimeter/submillimeter Array Large Program toward Oph IRS43, a binary system of solar mass protostars. The 1.3 mm dust continuum observations resolve a compact disk, ~6 au radius, around the northern component and show that the disk around the southern component is even smaller, ≲3 au. CO, 13CO, and C18O maps reveal a large cavity in a low-mass envelope that shows kinematic signatures of rotation and infall extending out to ~2000 au. An expanding CO bubble centered on the extrapolated location of the source ~130 yr ago suggests a recent outburst. Despite the small size of the disks, the overall picture is of a remarkably large and dynamically active region.

Keywords: protostars
Search for Extended Sources of Neutrino Emission in the Galactic Plane with IceCube

The Galactic plane, harboring a diffuse neutrino flux, is a particularly interesting target in which to study potential cosmic-ray acceleration sites. Recent gamma-ray observations by HAWC and LHAASO have presented evidence for multiple Galactic sources that exhibit a spatially extended morphology and have energy spectra continuing beyond 100 TeV. A fraction of such emission could be produced by interactions of accelerated hadronic cosmic rays, resulting in an excess of high-energy neutrinos clustered near these regions. Using 10 years of IceCube data comprising track-like events that originate from charged-current muon neutrino interactions, we perform a dedicated search for extended neutrino sources in the Galaxy. We find no evidence for time-integrated neutrino emission from the potential extended sources studied in the Galactic plane. The most significant location, at 2.6σ post-trials, is a 1.°7 sized region coincident with the unidentified TeV gamma-ray source 3HWC J1951+266. We provide strong constraints on hadronic emission from several regions in the galaxy.

Keywords: neutrino astronomy
Evidence for Magnetar Precession in X-Ray Afterglows of Gamma-Ray Bursts

Many gamma-ray bursts are followed by periods of extended emission. At least in some cases, the burst afterglow may be powered by a rapidly rotating, highly magnetized neutron star, which spins down due to electromagnetic and gravitational-wave emission. Such a remnant is likely to strongly precess in the early stages of its life, which would lead to modulations in the X-ray luminosity as the triaxiality of the system evolves over time. Using a radiation profile appropriate for a precessing, oblique rotator, we find that Swift-XRT data of a long (080602) and a short (090510) burst matches the model with significantly higher accuracy (mean-square residuals dropping by ≳200% in the early stages of the extended emission) than for an orthogonal rotator. We interpret this as evidence for precession in newborn magnetars.

Keywords: magnetars; gamma-ray bursts; stellar oscillations; magnetic fields
Impact of Changing Stellar and Planetary Magnetic Fields on (Exo)planetary Environments and Atmospheric Mass Loss

The magnetic activity of a star-which modulates the stellar wind outflow-shapes the immediate environments of orbiting (exo)planets and induces atmospheric loss, thereby impacting their habitability. We perform a detailed parameter space study using three-dimensional magnetohydrodynamic simulations to understand the effect of changing stellar wind magnetic field and planetary magnetic field strengths on planetary magnetospheric topology and atmospheric losses. It is observed that the relative strengths of stellar and planetary magnetic fields play a significant role in determining the steady-state magnetospheric configuration and atmospheric erosion. When the stellar field is strengthened or the planetary field is weakened, stellar magnetic field accumulation occurs at the dayside of the planet, forcing the magnetopause to shift closer to its surface. The magnetotail opens up, leading to the formation of Alfvén wings in the nightside wake region. We demonstrate how reconnection processes and wind conditions lead to the bifurcation of the magnetotail current sheet. With increasing stellar wind magnetic field strength, the dayside reconnection point approaches the planet, thereby enhancing mass loss. We establish an analytic equation relating the atmospheric mass-loss rates to stellar and planetary magnetic field strengths, which successfully explains the modeled behavior. Our results are relevant for understanding how the interplay of stellar and planetary magnetism influence (exo)planetary environments and their habitability in star-planet systems with differing relative magnetic field strengths or in a single star-planet system over the course of their evolution with age.

Keywords: stellar winds; planetary magnetospheres; exoplanet atmospheres; exoplanet atmospheric structure; star-planet interactions; magnetohydrodynamics
An Examination of Pulsational Changes in the Classical Cepheid X Cygni

Using an extensive archive for visual observations from the AAVSO, along with published times of maximum light, we determined a new model for the period of X Cygni. The best model is two linear fits for data before and after 1917 (JD2421512). Before that time the period is 16.38438 ± 0.00036 days. After we find a period of 16.386470 ± 0.000028 days. An examination of the O-C values for data after 1917 shows no clear evidence of a constant period change or of sinusoidal variations. The period looks to be constant. From an examination of H-alpha index measurements we find a drop in the value between data before 2013 October and data after 2014 July. This drop is not related to temperature and is likely related to mass loss in the star. Finally, we find that radial-velocity measurements match well with previously published values and show no seasonal variation over the 11 yr of data. This again seems to limit the possibility of a companion.

Keywords: cepheid variable stars; radial velocity; variable star period change
On the Theory of Ring Afterglows

Synchrotron and inverse Compton emission successfully explain the observed spectra of gamma-ray burst (GRB) afterglows. It is thought that most GRBs are products of extremely relativistic outflows and the afterglow marks the interaction of that ejecta with the surrounding matter. A faster decay of afterglow light curves at late times is indicative of nonspherical geometries, and is usually interpreted as evidence for jet geometry. Recent numerical simulations have shown that ring-like geometries are also permissible for relativistic outflows. We therefore extend the standard theory of afterglow evolution to ring geometries. An analytic prescription for the light curves and spectra produced by relativistic toroidal blast waves is presented. We compare these to their spherical and jet-like counterparts, and show that ring afterglows decay faster than spherical outflows but not as fast as jets.

Keywords: gamma-ray bursts; light curves; relativistic fluid dynamics