adsabs/SciX_UAT_keywords huggingface dataset:
Evidence of Early-stage Tidal Structures of Open Clusters Revealed by Kinematics with Gaia EDR3

Blanco 1, a 100 Myr open cluster in the solar neighborhood, is well known for its two 50 pc long tidal tails. Taking Blanco 1 as a reference, we find evidence of early-stage tidal disruption in two other open clusters of ~120 Myr: the Pleiades and NGC 2516, via Gaia EDR3 data. These two clusters have a total mass of 2-6 times that of Blanco 1. Despite having a similar age as Blanco 1, the Pleiades and NGC 2516 have a larger fraction of their members bound: 86% of their mass is inside the tidal radius, versus 63% for Blanco 1. However, a correlation between Blanco 1's 50 pc long tidal tails and the "kinematic tails" in velocity space is also found for the Pleiades and NGC 2516. This evidence supports the idea that the modest elongation seen in the spatial distribution for the Pleiades and NGC 2516 is a result of early-stage tidal disruption.

Keywords: open star clusters; stellar kinematics; tidal distortion
Chemical Modeling of Orion Nebula Cluster Disks: Evidence for Massive, Compact Gas Disks with Interstellar Gas-to-dust Ratios

The stellar cluster environment is expected to play a central role in the evolution of circumstellar disks. We use thermochemical modeling to constrain the dust and gas masses, disk sizes, UV and X-ray radiation fields, viewing geometries, and central stellar masses of 20 class II disks in the Orion Nebula Cluster (ONC). We fit a large grid of disk models to 350 GHz continuum, CO J = 3 - 2, and HCO+ J = 4 - 3 Atacama Large Millimeter/submillimeter Array observations of each target, and we introduce a procedure for modeling interferometric observations of gas disks detected in absorption against a bright molecular cloud background. We find that the ONC disks are massive and compact, with typical radii <100 au, gas masses ≥10-3 M ⊙, and gas-to-dust ratios ≥100. The interstellar‑medium‑like gas-to-dust ratios derived from our modeling suggest that compact, externally irradiated disks in the ONC are less prone to gas-phase CO depletion than the massive and extended gas disks that are commonly found in nearby low-mass star-forming regions. The presence of massive gas disks indicates that external photoevaporation may have only recently begun operating in the ONC; though it remains unclear whether other cluster members are older and more evaporated than the ones in our sample. Finally, we compare our dynamically derived stellar masses with the stellar masses predicted from evolutionary models and find excellent agreement. Our study has significantly increased the number of dynamical mass measurements in the mass range ≤0.5 M ⊙, demonstrating that the ONC is an ideal region for obtaining large samples of dynamical mass measurements toward low-mass M-dwarfs.

Keywords: protoplanetary disks; circumstellar disks; proplyds; young star clusters; young stellar objects; pre-main sequence stars; planet formation; radio astronomy; submillimeter astronomy
Resolving Massive Black Hole Binary Evolution via Adaptive Particle Splitting

The study of the interaction of a massive black hole binary with its gaseous environment is crucial in order to be able to predict merger rates and possible electromagnetic counterparts of gravitational-wave signals. The evolution of the binary semimajor axis resulting from this interaction has been recently debated, and a clear consensus is still missing because of several numerical limitations, i.e., fixed orbit binaries or lack of resolution inside the cavity carved by the binary in its circumbinary disk. Using on-the-fly particle splitting in the 3D meshless code GIZMO, we achieve hyper-Lagrangian resolution, which allows us to properly resolve the dynamics inside the cavity-in particular, for the first time, the disks that form around the two components of a live binary surrounded by a locally isothermal gaseous circumbinary disk. We show that the binary orbit decays with time for very cold and very warm disks and that the result of the interaction in the intermediate regime is strongly influenced by the disk viscosity, as this essentially regulates the fraction of mass contained in the disks around the binary components, as well as the fraction that is accreted by the binary. We find the balance between these two quantities to determine whether the binary semimajor axis decreases with time.

Keywords: stellar accretion disks; accretion; hydrodynamical simulations; binary stars; black holes
Erosion of Volatiles by Micrometeoroid Bombardment on Ceres and Comparison to the Moon and Mercury

Ceres, the largest reservoir of water in the main belt, was recently visited by the Dawn spacecraft, which revealed several areas bearing H2O-ice features. Independent telescopic observations showed a water exosphere of currently unknown origin. We explore the effects of meteoroid impacts on Ceres by considering the topography obtained from the Dawn mission using a widely used micrometeoroid model and ray-tracing techniques. Meteoroid populations with 0.01-2 mm diameters are considered. We analyze the short-term effects Ceres experiences during its current orbit, as well as long-term effects over the entire precession cycle. We find that the entire surface is subject to meteoroid bombardment, leaving no areas in permanent shadow with respect to meteoroid influx. The equatorial parts of Ceres produce 80% more ejecta than the polar regions due to the large impact velocity of long-period comets. Mass flux, energy flux, and ejecta production vary seasonally by a factor of 3-7 due to the inclined eccentric orbit. Compared to Mercury and the Moon, Ceres experiences significantly smaller effects of micrometeoroid bombardment, with a total mass flux of 4.5 ± 1.2 × 10-17 kg m-2 s-1. On average, Mercury is subjected to a 50× larger mass flux and generates 700× more ejecta than Ceres, while the lunar mass flux is 10× larger and the ejecta generation is 30× larger than on Ceres. For these reasons, we find that meteoroid impacts are an unlikely candidate for the production of a water exosphere or significant excavation of surface features. The surface turnover rate from the micrometeoroid populations considered is estimated to be 1.25 Myr on Ceres.

Keywords: zodiacal cloud; impact phenomena; mercury (planet); the moon; space weather; meteoroid dust clouds; micrometeoroids; meteoroids
Rotation, Convective Core Overshooting, and Period Changes in Classical Cepheid Stellar Evolution Models

Classical Cepheids are powerful probes of both stellar evolution and near-field cosmology thanks to their great luminosities, pulsations, and their adherence to the Leavitt (period-luminosity) Law. However, there still exist a number of questions regarding their evolution, such as the roles of rotation, convective core overshooting, and winds. ln particular, how do these processes impact Cepheid evolution and the predicted fundamental properties such as stellar mass? In this work, we compare a sample of Cepheids with measured rates of period change with new evolution models to test the impact of these first two processes. In our previous study we found that enhanced mass loss is crucial for describing the sample, and here we continue that analysis but for rotational mixing and core overshooting. We show that while rotation is important for stellar evolution studies, rotation itself is insufficient to model the distribution of period change rates from the observed sample. On the other hand, convective core overshooting is needed to explain the magnitude of the rates of period change, but does not explain the number of stars with positive and negative period change rates. In conclusion, we determine that convective core overshooting and stellar rotation alone are not enough to account for the observed distribution of Cepheid rates of period change and another mechanism, such as pulsation-driven mass loss, may be required.

Keywords: stellar evolution; fundamental parameters of stars; stellar mass loss; delta cepheid variable stars
Radio and X-Ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare

Solar flares are sudden energy release events in the solar corona, resulting from magnetic reconnection, that accelerate particles and heat the ambient plasma. During a flare, there are often multiple temporally and spatially separated individual energy release episodes that can be difficult to resolve depending on the observing instrument. We present multiwavelength imaging and spectroscopy observations of multiple electron acceleration episodes during a GOES B1.7-class two-ribbon flare on 2012 February 25, observed simultaneously with the Karl G. Jansky Very Large Array at 1-2 GHz, the Reuven Ramatay High Energy Solar Spectroscopic Imager in X-rays, and the Solar Dynamics Observatory in extreme ultraviolet. During the initial phase of the flare, five radio bursts were observed. A nonthermal X-ray source was seen to be cotemporal but not cospatial with the first three radio bursts. Their radio spectra are interpreted as optically thick gyrosynchrotron emission. By fitting the radio spectra with a gyrosynchrotron model, we derive the magnetic field strength and nonthermal electron spectral parameters in each acceleration episode. Notably, the nonthermal parameters derived from X-rays differ considerably from the nonthermal parameters inferred from the radio. The observations are indicative of multiple cotemporal acceleration episodes during the impulsive phase of a solar microflare. The X-ray and radio burst sources likely originate from separate electron distributions in different magnetic loops.

Keywords: the sun; solar flares; solar energetic particles; solar radio flares; solar radio emission
Kinematic Evidence of an Embedded Protoplanet in HD 142666 Identified by Machine Learning

Observations of protoplanetary disks have shown that forming exoplanets leave characteristic imprints on the gas and dust of the disk. In the gas, these forming exoplanets cause deviations from Keplerian motion, which can be detected through molecular line observations. Our previous work has shown that machine learning can correctly determine if a planet is present in these disks. Using our machine-learning models, we identify strong, localized non-Keplerian motion within the disk HD 142666. Subsequent hydrodynamics simulations of a system with a 5 M J planet at 75 au recreate the kinematic structure. By currently established standards in the field, we conclude that HD 142666 hosts a planet. This work represents a first step toward using machine learning to identify previously overlooked non-Keplerian features in protoplanetary disks.

Keywords: protoplanetary disks; planetary system formation; hydrodynamical simulations; astronomical simulations; radiative transfer simulations
Gap-opening Planets Make Dust Rings Wider

As one of the most commonly observed disk substructures, dust rings from high-resolution disk surveys appear to have different radial widths. Recent observations on PDS 70 and AB Aur reveal not only planets in the disk, but also the accompanying wide dust rings. We use three-dimensional dust-and-gas disk simulations to study whether gap-opening planets are responsible for the large ring width in disk observations. We find that gap-opening planets can widen rings of dust trapped at the pressure bump via planetary perturbations, even with the midplane dust-to-gas ratio approaching order unity and with the dust back-reaction accounted for. We show that the planet-related widening effect of dust rings can be quantified using diffusion-advection theory, and we provide a generalized criterion for an equilibrated dust ring width in three-dimensional disk models. We also suggest that the ring width can be estimated using the gas turbulent viscosity α turb, but with cautions about the Schmidt number being greater than order unity.

Keywords: protoplanetary disks; planet formation; circumstellar dust; astrophysical dust processes; astronomical simulations
Fractionation of Solar Wind Minor Ion Precipitation by the Lunar Paleomagnetosphere

The analysis of solar wind material implanted within lunar soil has provided significant insight into the makeup and evolutionary history of the solar wind and, by extension, the Sun and protosolar nebula. These analyses often rely on the tacit assumption that the Moon has served as an unbiased recorder of solar wind composition over its 4.5 billion yr lifetime. Recent work, however, has shown that for a majority of its lifetime, the Moon has possessed a dynamo that generates a global magnetic field with surface field strengths of at least 5 μT. In turn, the presence of such a field has been shown to significantly alter the lunar-solar wind interaction via the formation of a lunar "paleomagnetosphere." This paleomagnetosphere has implications for the flux of solar wind minor ions to the lunar surface and their subsequent implantation in lunar soil grains. Here we use a three-dimensional hybrid plasma model to investigate the effects of the lunar paleomagnetosphere on the dynamics and precipitation of solar wind minor ions to the lunar surface. The model results show that the lunar paleomagnetosphere can suppress minor ion fluxes to the lunar surface by more than an order of magnitude and strongly fractionates the precipitating solar wind in a complex, nonlinear fashion with respect to both the minor ion charge-to-mass ratio and the surface paleomagnetic field strength. We discuss the implications of these results with respect to both the analysis of trapped material in lunar grains and the semiquantitative 40Ar/36Ar antiquity indicator for lunar soils.

Keywords: the moon; lunar magnetic fields; planetary magnetospheres; solar wind
The Effects of Large-scale Magnetic Fields on the Model for Repeating Changing-look AGNs

Periodic outbursts are observed in several changing-look (CL) active galactic nuclei (AGNs). Sniegowska et al. suggested a model to explain the repeating CL in these AGNs, where the periodic outbursts are triggered in a narrow unstable zone between an inner advection-dominated accretion flow and outer thin disk. In this work, we intend to investigate the effects of large-scale magnetic fields on the limit cycle behaviors of CL AGNs. The winds driven by magnetic fields can significantly change the structure of thin disk by taking away the angular momentum and energy of the disk. It is found that the period of outburst in repeating CL AGNs can be substantially reduced by the magnetic fields. Conversely, if we keep the period unchanged, the outburst intensity can be raised by several times. These results can help to explain the observational properties of multiple CL AGNs. Besides the magnetic fields, the effects of transition radius ${R}_{\mathrm{tr}}$ <!-- --> , the width of the transition zone ΔR, and the Shakura-Sunyaev parameter α are also explored in this work.

Keywords: magnetic fields; galaxy accretion disks; active galactic nuclei
Introducing the Texas Euclid Survey for Lyα (TESLA) Survey: Initial Study Correlating Galaxy Properties to Lyα Emission

We present the Texas Euclid Survey for Lyα (TESLA), a spectroscopic survey in the 10 deg2 of the Euclid North Ecliptic Pole (NEP) field. Using TESLA, we study how the physical properties of Lyα emitters (LAEs) correlate with Lyα emission to understand the escape of Lyα emission from galaxies at redshifts of 2-3.5. We present an analysis of 43 LAEs performed in the NEP field using early data from the TESLA survey. We use Subaru Hyper Suprime-Cam imaging in the grizy bands, Spitzer/IRAC channels 1 and 2 from the Hawaii 20 deg2 (H20) survey, and spectra acquired by the Visible Integral-Field Replicable Unit Spectrograph (VIRUS) on the Hobby-Eberly Telescope. We perform spectral energy distribution (SED) fitting to compute the galaxy properties of 43 LAEs, and study correlations between stellar mass, star formation rate (SFR), and dust to the Lyα rest-frame equivalent width (W Lyα ). We uncover marginal (1σ significance) correlations between stellar mass and W Lyα , and SFR and W Lyα , with a Spearman correlation coefficient of -0. ${34}_{-.14}^{+.17}$ and -0. ${37}_{-.14}^{+.16}$ , respectively. We show that the W Lyα distribution of the 43 LAEs is consistent with being drawn from an exponential distribution with an e-folding scale of W 0 = 150 Å. Once complete the TESLA survey will enable the study of ≳50,000 LAEs to explore more correlations between galaxy properties and W Lyα . The large sample size will allow the construction of a predictive model for W Lyα as a function of SED-derived galaxy properties, which could be used to improve Lyα-based constraints on reionization.

Keywords: galaxies; surveys; reionization; lyman-alpha galaxies
Solar Filament Detection Based on Improved DeepLab V3+

A novel solar filament detection method based on an improved DeepLab V3+ is proposed to address the low detection accuracy of small solar filaments in Hα full-disk solar images. First, the Xception structure of the backbone network is fine-tuned, and the low-level feature information of the filaments is added to the decoder module of the network to improve the utilization of the solar filament features. Second, the receptive field of dilated convolution is expanded, and the information utilization rate is increased via cascaded dilated convolution to improve the detection accuracy of the small solar filaments. In the decoder module, two depthwise separable convolutions are used instead of ordinary convolutions to reduce incomplete detections. Finally, a dense conditional random field is added to optimize the edge of the detection results. Experiments on a public data set comprising full-disk Hα images show that compared with the original Deeplab V3+ algorithm, the proposed method improves the mean pixel accuracy, mean intersection over union, and F1-score by 1.86%, 1.95%, and 2.18%, respectively, which also demonstrates its superiority over other existing solar filament detection algorithms.

Keywords: solar filaments; detection; convolutional neural networks
Asteroseismology and Spectropolarimetry of the Exoplanet Host Star λ Serpentis

The bright star λ Ser hosts a hot Neptune with a minimum mass of 13.6 M ⊕ and a 15.5 day orbit. It also appears to be a solar analog, with a mean rotation period of 25.8 days and surface differential rotation very similar to the Sun. We aim to characterize the fundamental properties of this system and constrain the evolutionary pathway that led to its present configuration. We detect solar-like oscillations in time series photometry from the Transiting Exoplanet Survey Satellite, and we derive precise asteroseismic properties from detailed modeling. We obtain new spectropolarimetric data, and we use them to reconstruct the large-scale magnetic field morphology. We reanalyze the complete time series of chromospheric activity measurements from the Mount Wilson Observatory, and we present new X-ray and ultraviolet observations from the Chandra and Hubble space telescopes. Finally, we use the updated observational constraints to assess the rotational history of the star and estimate the wind braking torque. We conclude that the remaining uncertainty on the stellar age currently prevents an unambiguous interpretation of the properties of λ Ser, and that the rate of angular momentum loss appears to be higher than for other stars with a similar Rossby number. Future asteroseismic observations may help to improve the precision of the stellar age.

Keywords: spectropolarimetry; stellar activity; stellar evolution; stellar oscillations; stellar rotation
Gamma-Ray Burst Detection with Poisson-FOCuS and Other Trigger Algorithms

We describe how a novel online change-point detection algorithm, called Poisson-FOCuS, can be used to optimally detect gamma-ray bursts within the computational constraints imposed by miniaturized satellites such as the upcoming HERMES-Pathfinder constellation. Poisson-FOCuS enables testing for gamma-ray burst onset at all intervals in a count time series, across all timescales and offsets, in real time and at a fraction of the computational cost of conventional strategies. We validate an implementation with automatic background assessment through exponential smoothing, using archival data from Fermi-GBM. Through simulations of lightcurves modeled after real short and long gamma-ray bursts, we demonstrate that the same implementation has higher detection power than algorithms designed to emulate the logic of Fermi-GBM and Compton-BATSE, reaching the performance of a brute-force benchmark with oracle information on the true background rate, when not hindered by automatic background assessment. Finally, using simulated data with different lengths and means, we show that Poisson-FOCuS can analyze data twice as fast as a similarly implemented benchmark emulator for the historic Fermi-GBM on-board trigger algorithms.

Keywords: astrostatistics techniques; algorithms; transient detection; gamma-ray bursts; artificial satellites
Subseasonal Variation in Neptune's Mid-infrared Emission

We present an analysis of all currently available ground-based imaging of Neptune in the mid-infrared. Dating between 2003 and 2020, the images reveal changes in Neptune's mid-infrared (~8-25 μm) emission over time in the years surrounding Neptune's 2005 southern summer solstice. Images sensitive to stratospheric ethane (~12 μm), methane (~8 μm), and CH3D (~9 μm) display significant subseasonal temporal variation on regional and global scales. Comparison with H2 S(1) hydrogen quadrupole (~17.035 μm) spectra suggests that these changes are primarily related to stratospheric temperature changes. The stratosphere appears to have cooled between 2003 and 2009 across multiple filtered wavelengths, followed by a dramatic warming of the south pole between 2018 and 2020. Conversely, upper-tropospheric temperatures-inferred from ~17 to 25 μm imaging-appear invariant during this period, except for the south pole, which appeared warmest between 2003 and 2006. We discuss the observed variability in the context of seasonal forcing, tropospheric meteorology, and the solar cycle. Collectively, these data provide the strongest evidence to date that processes produce subseasonal variation on both global and regional scales in Neptune's stratosphere.

Keywords: atmospheric variability; planetary science; atmospheric science; solar system astronomy; planetary atmospheres; neptune; atmospheric circulation; atmospheric composition; atmospheric clouds
Kilonova Emission from Black Hole-Neutron Star Mergers. I. Viewing-angle-dependent Lightcurves

In this paper, we explore the viewing angle effect on black hole-neutron star (BH-NS) merger kilonova lightcurves. We extrapolate the fitting formulae for the mass and velocity of dynamical ejecta across a wide mass ratio range validated with 66 simulations and use them in kilonova lightcurve calculations. The calculated peak luminosity of a BH-NS merger kilonova is typically about a few times 1041 erg s-1, which is always ≲4.5 × 1041 erg s-1. This corresponds to AB absolute magnitudes fainter than ∼-15 mag in the optical and ∼-16 mag in the infrared. The dynamical ejecta usually contribute to the majority of the kilonova emission, as its projected photosphere area is much larger than that of the disk wind outflows. The fitted blackbody temperature and the observed multiband lightcurve shape are insensitive to the line of sight. The peak time of the observed multiband lightcurves, affected by the light-propagation effect, is related to the relative motion direction between the dynamical ejecta and the observer. The predicted peak luminosity, which changes with the projected photosphere area, only varies by a factor of ∼(2-3) (or by ∼1 mag) for different viewing angles. When taking the short-duration gamma-ray burst afterglow into account, for an on-axis geometry, the kilonova emission is usually outshone by the afterglow emission and can only be observed in the redder bands, especially in the K band at late times. Compared with GW 170817/AT 2017gfo, BH-NS merger kilonovae are optically dim but possibly infrared bright, and have lower fitting temperature at the same epoch after the merger.

Keywords: neutron stars; gamma-ray bursts; gravitational waves; black holes