adsabs/SciX_UAT_keywords huggingface dataset:
High-contrast Imaging around a 2 Myr-old CI Tau with a Close-in Gas Giant

Giant planets around young stars serve as a clue to unveiling their formation history and orbital evolution. CI Tau is a 2 Myr-old classical T Tauri star hosting an eccentric hot Jupiter, CI Tau b. The standard formation scenario of a hot Jupiter predicts that planets formed further out and migrated inward. A high eccentricity of CI Tau b may be suggestive of high-e migration due to secular gravitational perturbations by an outer companion. Also, the Atacama Large Millimeter/submillimeter Array 1.3 mm-continuum observations show that CI Tau has at least three annular gaps in which unseen planets may exist. We present high-contrast imaging around CI Tau taken from the Keck/NIRC2 ${L}^{{\prime} }$ -band filter and vortex coronagraph that allows us to search for an outer companion. We did not detect any outer companion around CI Tau from angular differential imaging (ADI) using two deep imaging data sets. The detection limits from ADI-reduced images rule out the existence of an outer companion beyond ~30 au that can cause the Kozai-Lidov migration of CI Tau b. Our results suggest that CI Tau b may have experienced type II migration from ≲2 au in megayears. We also confirm that no planets with ≥2-4 M Jup are hidden in two outer gaps.

Keywords: direct imaging; planet formation; protoplanetary disks; planetary migration
Understanding the Origin of the Magnetic Field Morphology in the Wide-binary Protostellar System BHR 71

We present 1.3 mm Atacama Large Millimeter/submillimeter Array observations of polarized dust emission toward the wide-binary protostellar system BHR 71 IRS1 and IRS2. IRS1 features what appears to be a natal, hourglass-shaped magnetic field. In contrast, IRS2 exhibits a magnetic field that has been affected by its bipolar outflow. Toward IRS2, the polarization is confined mainly to the outflow cavity walls. Along the northern edge of the redshifted outflow cavity of IRS2, the polarized emission is sandwiched between the outflow and a filament of cold, dense gas traced by N2D+, toward which no dust polarization is detected. This suggests that the origin of the enhanced polarization in IRS2 is the irradiation of the outflow cavity walls, which enables the alignment of dust grains with respect to the magnetic field - but only to a depth of ∼300 au, beyond which the dust is cold and unpolarized. However, in order to align grains deep enough in the cavity walls, and to produce the high polarization fraction seen in IRS2, the aligning photons are likely to be in the mid- to far-infrared range, which suggests a degree of grain growth beyond what is typically expected in very young, Class 0 sources. Finally, toward IRS1 we see a narrow, linear feature with a high (10%-20%) polarization fraction and a well-ordered magnetic field that is not associated with the bipolar outflow cavity. We speculate that this feature may be a magnetized accretion streamer; however, this has yet to be confirmed by kinematic observations of dense-gas tracers.

Keywords: astrochemistry; compact radiation sources; polarimetry; dust continuum emission; star formation; protostars; wide binary stars; interstellar dust; young stellar objects; interstellar magnetic fields
Detection of p-mode Oscillations in HD 35833 with NEID and TESS

We report the results of observations of p-mode oscillations in the G0 subgiant star HD 35833 in both radial velocities and photometry with NEID and TESS, respectively. We achieve separate, robust detections of the oscillation signal with both instruments (radial velocity amplitude A RV = 1.11 ± 0.09 m s-1, photometric amplitude A phot = 6.42 ± 0.60 ppm, frequency of maximum power ${\nu }_{\max }=595.71\pm 17.28$ μHz, and mode spacing Δν = 36.65 ± 0.96 μHz) as well as a nondetection in a TESS sector concurrent with the NEID observations. These data shed light on our ability to mitigate the correlated noise impact of oscillations with radial velocities alone and on the robustness of commonly used asteroseismic scaling relations. The NEID data are used to validate models for the attenuation of oscillation signals for exposure times $t\lt {\nu }_{\max }^{-1}$ , and we compare our results to predictions from theoretical scaling relations and find that the observed amplitudes are weaker than expected by >4σ, hinting at gaps in the underlying physical models.

Keywords: asteroseismology; exoplanet detection methods; radial velocity; stellar astronomy; black hole thermodynamics
GIGA-Lens: Fast Bayesian Inference for Strong Gravitational Lens Modeling

We present GIGA-Lens: a gradient-informed, GPU-accelerated Bayesian framework for modeling strong gravitational lensing systems, implemented in TensorFlow and JAX. The three components, optimization using multistart gradient descent, posterior covariance estimation with variational inference, and sampling via Hamiltonian Monte Carlo, all take advantage of gradient information through automatic differentiation and massive parallelization on graphics processing units (GPUs). We test our pipeline on a large set of simulated systems and demonstrate in detail its high level of performance. The average time to model a single system on four Nvidia A100 GPUs is 105 s. The robustness, speed, and scalability offered by this framework make it possible to model the large number of strong lenses found in current surveys and present a very promising prospect for the modeling of ${ \mathcal O }({10}^{5})$ lensing systems expected to be discovered in the era of the Vera C. Rubin Observatory, Euclid, and the Nancy Grace Roman Space Telescope.

Keywords: gpu computing; markov chain monte carlo; strong gravitational lensing; einstein rings; bayesian statistics; cosmology
CASA, the Common Astronomy Software Applications for Radio Astronomy

CASA, the Common Astronomy Software Applications, is the primary data processing software for the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA), and is frequently used also for other radio telescopes. The CASA software can handle data from single-dish, aperture-synthesis, and Very Long Baseline Interferometery (VLBI) telescopes. One of its core functionalities is to support the calibration and imaging pipelines for ALMA, VLA, VLA Sky Survey, and the Nobeyama 45 m telescope. This paper presents a high-level overview of the basic structure of the CASA software, as well as procedures for calibrating and imaging astronomical radio data in CASA. CASA is being developed by an international consortium of scientists and software engineers based at the National Radio Astronomy Observatory (NRAO), the European Southern Observatory, the National Astronomical Observatory of Japan, and the Joint Institute for VLBI European Research Infrastructure Consortium (JIV-ERIC), under the guidance of NRAO.

Keywords: single-dish antennas; aperture synthesis; radio astronomy; radio interferometry; long baseline interferometry; astronomy software; open source software; software documentation; astronomy data reduction; astronomy data analysis
Timing and Abundance of Clathrate Formation Control Ocean Evolution in Outer Solar System Bodies: Challenges of Maintaining a Thick Ocean within Pluto

Clathrate hydrates may represent a sizable fraction of material within the icy shells of Kuiper Belt objects and icy moons. They influence the chemical and thermal evolution of subsurface oceans by locking volatiles into the ice shell and by providing more thermal insulation than pure water ice. We model the formation of these crystalline compounds in conditions relevant to outer solar system objects, using Pluto as an example. Although Pluto may have hosted a thick ocean in its early history, Pluto's overall heat budget is probably insufficient to preserve liquid today if its outer shell is pure water ice. One previously proposed reconciliation is that Pluto's ocean has a winter jacket: an insulating layer of methane clathrate hydrates. Unfortunately, assessments of the timing, quantity, and type of clathrate hydrates forming within planetary bodies are lacking. Our work quantifies the abundance of clathrate-forming gases present in Pluto's ocean from accreted ices and volatiles released during thermal metamorphism throughout Pluto's history. We find that if Pluto formed with the same relative abundances of ices found in comets, then a buoyant layer of mixed methane and carbon dioxide clathrate hydrates may form above Pluto's ocean, though we find it insufficient to preserve a thick ocean today. In general, our study provides methodology for predicting clathrate formation in ocean worlds, which is necessary to predict the evolution of the ocean's composition and whether a liquid layer remains at present.

Keywords: pluto; planetary thermal histories; planetary interior; chemical abundances
KIC 10975348: A Double-mode or Triple-mode High-amplitude δ Scuti Star?

In this paper, we analyze the light variations of KIC 10975348 using photometric data delivered from the Kepler mission. This star is exceptionally faint (Kp = 18.6 mag) compared to most well-studied δ Scuti stars. The Fourier analysis of the short-cadence data (i.e., Q14, Q15, and Q16, spanning 220 days) reveals that the variations are dominated by the strongest mode with a frequency of F0 = 10.231899 day-1, which is compatible with that obtained from RATS-Kepler. The other two independent modes with F1 (=13.4988 day-1) and F2 (=19.0002 day-1) are newly detected and have amplitudes two orders of magnitude smaller than F0. We note that, for the first time, this star is identified to be a high-amplitude δ Sct (HADS) star with an amplitude of about 0.7 mag, and the lower ratio of F0/F1 = 0.758 suggests that it might be a metal-rich variable star. The frequency F2 may be a third overtone mode, suggesting that this target might be a new radial triple-mode HADS star. We perform an O - C analysis using 1018 newly determined times of maximum light and derive an ephemeris formula of Tmax = 2456170.241912(0)+0.097734(1) × E. The O - C diagram shows that the pulsation period of KIC 10975348 seems to show no obvious change, which is in contrast to that of the majority of HADS stars. The possible cause of that may be due to the current short time span of the observations. To verify its possible period variations, regular observation from space with a longer time span in the future is needed.

Keywords: stellar oscillations; delta scuti variable stars; short period variable stars
Evaporation from the Lunar Magma Ocean Was Not the Mechanism for Fractionation of the Moon's Moderately Volatile Elements

The cause of chemical depletion and isotopic fractionation of moderately volatile elements (MVEs) in the Moon is a long-standing problem. Here we examine MVE isotopic fractionation during Moon formation using potassium as a primary example. We show that the degree of isotopic fractionation due to evaporation of the lunar magma ocean (LMO) depended critically on the vapor pressure above the LMO. Based on our analysis of evaporation and escape of the resulting rock-vapor atmosphere, LMO evaporation alone could not have caused the observed MVE isotopic compositions. The combination of exposure of the liquid of the LMO to the surface for on the order of 102-103 yr, near-equilibrium evaporation at the melt surface, and hydrodynamic escape facilitated by proximity of the Earth leads to no resolvable isotope or elemental fractionation. This study provides a basis for the simplifying assumption that rock vapor immediately above a magma ocean will be in thermodynamic equilibrium with the melt at the surface of the planetary body even where hydrodynamic escape is operative.

Keywords: earth-moon system; isotope shifts; lunar evolution; the moon; lunar science
The Ariel Target List: The Impact of TESS and the Potential for Characterizing Multiple Planets within a System

The ESA Ariel mission has been adopted for launch in 2029 and will conduct a survey of around 1000 exoplanetary atmospheres during its primary mission life. By providing homogeneous data sets with a high signal-to-noise ratio and wide wavelength coverage, Ariel will unveil the atmospheric demographics of these faraway worlds, helping to constrain planet formation and evolution processes on a galactic scale. Ariel seeks to undertake a statistical survey of a diverse population of planets; therefore, the sample of planets from which this selection can be made is of the utmost importance. While many suitable targets have already been found, hundreds more will be discovered before the mission is operational. Previous studies have used predictions of exoplanet detections to forecast the available planet population by the launch date of Ariel, with the most recent noting that the Transiting Exoplanet Survey Satellite (TESS) alone should provide over 1000 potential targets. In this work, we consider the planet candidates found to date by TESS to show that, with the addition of already confirmed planets, Ariel will already have a more than sufficient sample to choose its target list from once these candidates are validated. We showcase the breadth of this population, as well as exploring, for the first time, the ability of Ariel to characterize multiple planets within a single system. Comparative planetology of worlds orbiting the same star, as well as across the wider population, will undoubtedly revolutionize our understanding of planet formation and evolution.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; exoplanet systems; exoplanet catalogs; infrared telescopes; infrared observatories; infrared astronomical satellite
A New Covariant Formalism for Kinetic Plasma Simulations in Curved Spacetimes

Low-density plasmas are characterized by a large-scale separation between the gyromotion of particles around local magnetic fields and the macroscopic scales of the system, often making global kinetic simulations computationally intractable. The guiding center formalism has been proposed as a powerful tool to bridge the gap between these scales. Despite its usefulness, the guiding center approach has been formulated successfully only in flat spacetimes, limiting its applicability in astrophysical settings. Here, we present a new covariant formalism that leads to kinetic equations in the guiding center limit that are valid in arbitrary spacetimes. Through a variety of experiments, we demonstrate that our equations capture all known gyrocenter drifts while overcoming one severe limitation imposed on numerical algorithms by the fast timescales of the particle gyromotion. This formalism will enable explorations of a variety of global plasma kinetic phenomena in the curved spacetimes around black holes and neutron stars.

Keywords: plasma astrophysics; plasma physics; accretion; classical black holes; black holes
A Gaia Survey for Young Stars Associated with the Lupus Clouds

I have used high-precision photometry and astrometry from the second data release of the Gaia mission to perform a survey for young stars associated with the Lupus clouds, which have distances of ∼160 pc and reside within the Scorpius-Centaurus (Sco-Cen) OB association. The Gaia data have made it possible to distinguish Lupus members from most of the stars in other groups in Sco-Cen that overlap with the Lupus clouds, which have contaminated previous surveys. The new catalog of candidate Lupus members should be complete for spectral types earlier than M7 at AK < 0.2 within fields encompassing clouds 1-4. I have used that catalog to characterize various aspects of the Lupus stellar population. For instance, the sequence of low-mass stars in Lupus is ∼0.4 mag brighter than the sequence for Upper Sco, which implies an age of ∼6 Myr based an adopted age of 10-12 Myr for Upper Sco and the change in luminosity with age predicted by evolutionary models. I also find that the initial mass function in Lupus is similar to that in other nearby star-forming regions based on a comparison of their distributions of spectral types. * Based on observations made with the Gaia mission, the Two Micron All Sky Survey, the Wide-field Infrared Survey Explorer, the Spitzer Space Telescope, and the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey.

Keywords: brown dwarfs; star formation; initial mass function; low mass stars; ob associations; stellar associations; circumstellar disks; protoplanetary disks
Removal of Active Region Inflows Reveals a Weak Solar Cycle Scale Trend in the Near-surface Meridional Flow

Using time-distance local helioseismology flow maps within 1 Mm of the solar photosphere, we detect inflows toward activity belts that contribute to solar-cycle scale variations in the near-surface meridional flow. These inflows stretch out as far as 30° away from the active region centroids. If active region neighborhoods are excluded, the solar-cycle-scale variation in the background meridional flow diminishes to below 2 m s-1, but still shows systematic variations in the absence of active regions between sunspot cycles 24 and 25. We therefore propose that the near-surface meridional flow is a three-component flow made up of a constant baseline flow profile that can be derived from quiet-Sun regions, variations due to inflows around active regions, and solar-cycle-scale variation of about 2 m s-1. Torsional oscillation, on the other hand, is found to be a global phenomenon, i.e., exclusion of active region neighborhoods does not significantly affect its magnitude or phase. This nonvariation in torsional oscillation with distance away from active regions and the three-component breakdown of the near-surface meridional flow serve as vital constraints for solar dynamo models and surface flux-transport simulations.

Keywords: solar meridional circulation; helioseismology; solar dynamo; solar magnetic fields; solar cycle; solar active region velocity fields; solar active regions; solar active region magnetic fields; solar differential rotation; solar surface; solar physics; solar interior
Bright Supernova Precursors by Outbursts from Massive Stars with Compact Object Companions

A fraction of core-collapse supernovae (SNe) with signs of interaction with a dense circumstellar matter are preceded by bright precursor emission. While the precursors are likely caused by a mass ejection before core collapse, their mechanism to power energetic bursts—sometimes reaching 1048–1049 erg, which is larger than the binding energies of red supergiant envelopes—is still under debate. Remarkably, such a huge energy deposition should result in an almost complete envelope ejection and hence a strong sign of interaction, but the observed SNe with precursors show in fact typical properties among the interacting SNe. More generally, the observed luminosity of 1040‑1042 erg s‑1 is shown to be challenging for a single SN progenitor. To resolve these tensions, we propose a scenario where the progenitor is in a binary system with a compact object (CO) and an outburst from the star leads to a super-Eddington accretion onto the CO. We show that for sufficiently short separations outbursts with moderate initial kinetic energies of 1046–1047 erg can be energized by the accreting CO so that their radiative output can be consistent with the observed precursors. We discuss the implications of our model in relation to CO binaries detectable with Gaia and gravitational-wave detectors.

Keywords: eruptive phenomena; stellar mass loss; circumstellar matter; core-collapse supernovae
Localizing Sources of Variability in Crowded TESS Photometry

The Transiting Exoplanet Survey Satellite (TESS) has an exceptionally large plate scale of 21″ px-1, causing most TESS light curves to record the blended light of multiple stars. This creates a danger of misattributing variability observed by TESS to the wrong source, which would invalidate any analysis. We developed a method that can localize the origin of variability on the sky to better than one fifth of a pixel. Given measured frequencies of variability (e.g., from periodogram analysis), we show that the best-fit sinusoid amplitudes to raw light curves extracted from each pixel are distributed in the same way as light from the variable source. The primary assumption of this method is that other nearby stars are not variable at the same frequencies. Essentially, we are using the high frequency resolution of TESS to overcome limitations from its low spatial resolution. We have implemented our method in an open-source Python package, TESS_localize (github.com/Higgins00/TESS-Localize), that determines the location of a variable source on the sky and the most likely Gaia source given TESS pixel data and a set of observed frequencies of variability. Our method utilizes models of the TESS pixel response function, and we characterize systematics in the residuals of fitting these models to data. We find that even stars more than three pixels outside a photometric aperture can produce significant contaminant signals in the extracted light curves. Given the ubiquity of source blending in TESS light curves, verifying the source of observed variability should be a standard step in TESS analyses.

Keywords: astronomical object identification; ccd photometry; time series analysis; variable stars
Seeing-sorted Visible Multi-Object Spectrograph U-band Imaging of the GOODS-south Field

We present the optimal resolution and optimal depth U-filter mosaics using the seeing-sorted method of Ashcraft et al. on deep, ground-based U-bandimaging of the Great Observatories Origins Deep Survey South field as part of the near-UV imaging program UVCANDELS. We use the U-bandimages obtained with the VIsible Multi-Object Spectrograph on the European Southern Observatory Very Large Telescope by Nonino et al. Our best resolution mosaic includes images with a seeing full-width half maximum (FWHM) ≤ 0"8, and encompasses 50% of the data. Our best depth mosaic includes images with FWHM ≤ 1"5, corresponding to 100% of the data. Prior to being combined, the source fluxes in each individual background-subtracted image are corrected to match a 3D-HST photometric catalog of the same field to correct variations in the U-band zero-points. These mosaics provide deep U-banddata complementary to the UVCANDELS HST WFC3 F275W and ACS F435W images. We assess the depth of both U-bandmosaics. * Based on data acquired using the Very Large Telescope (VLT) of the European Southern Observatory (ESO).

Keywords: ultraviolet astronomy; astronomical seeing; astronomy data analysis
CRAFTS for Fast Radio Bursts: Extending the Dispersion-Fluence Relation with New FRBs Detected by FAST

We report three new FRBs discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), namely FRB 181017.J0036+11, FRB 181118, and FRB 181130, through the Commensal Radio Astronomy FAST Survey (CRAFTS). Together with FRB 181123, which was reported earlier, all four FAST-discovered FRBs share the same characteristics of low fluence (≤0.2 Jy ms) and high dispersion measure (DM, >1000 pc cm-3), consistent with the anticorrelation between DM and fluence of the entire FRB population. FRB 181118 and FRB 181130 exhibit band-limited features. FRB 181130 is prominently scattered (τs ≃ 8 ms) at 1.25 GHz. FRB 181017.J0036+11 has full-bandwidth emission with a fluence of 0.042 Jy ms, which is one of the faintest FRB sources detected so far. CRAFTS has started to build a new sample of FRBs that fills the region for more distant and fainter FRBs in the fluence-DME diagram, previously out of reach of other surveys. The implied all-sky event rate of FRBs is ${1.24}_{-0.90}^{+1.94}\times {10}^{5}$ sky-1 day-1 at the 95% confidence interval above 0.0146 Jy ms. We also demonstrate here that the probability density function of CRAFTS FRB detections is sensitive to the assumed intrinsic FRB luminosity function and cosmological evolution, which may be further constrained with more discoveries.

Keywords: radio transient sources; radio astronomy; radio bursts; astronomical object identification