adsabs/SciX_UAT_keywords huggingface dataset:
A New Lever on Exoplanetary B Fields: Measuring Heavy Ion Velocities

Magnetic fields connect an array of planetary processes, from atmospheric escape to interior convection. Despite their importance, exoplanet magnetic fields are largely unconstrained by both theory and observation. In this Letter, we propose a novel method for constraining the B field strength of hot gas giants: comparing the velocities of heavy ions and neutral gas with high-resolution spectroscopy. The core concept of this method is that ions are directly deflected by magnetic fields. While neutrals are also affected by B fields via friction with field-accelerated ions, ionic gas should be more strongly coupled to the underlying magnetic field than bulk neutral flow. Hence, measuring the difference between the two velocities yields rough constraints on the B field, provided an estimate of the stellar UV flux is known. We demonstrate that heavy ions are particularly well suited for this technique because they are less likely to be entrained in complex hydrodynamic outflows than their lighter counterparts. We perform a proof-of-concept calculation with Ba II, an ion whose velocity has been repeatedly measured at high confidence with high-resolution spectroscopy. Our work shows that a 10 G magnetic field would produce ∼1 km s‑1 ion–neutral velocity differences at a microbar, whereas a 50 G magnetic field would produce ∼20 km s‑1 velocity difference. With new leverage on magnetic fields, we will be able to investigate magnetic field generation in the extreme edge cases of hot gas giants, with wide-ranging consequences for planetary interior structure, dynamo theory, and habitability.

Keywords: hot jupiters; magnetohydrodynamics; exoplanets; exoplanet atmospheric dynamics; magnetic fields; exoplanet atmospheres
Supernova Precursor Emission and the Origin of Pre-explosion Stellar Mass Loss

A growing number of core-collapse supernovae (SNe) that show evidence for interaction with dense circumstellar medium (CSM) are accompanied by "precursor" optical emission rising weeks to months prior to the explosion. The precursor luminosities greatly exceed the Eddington limit of the progenitor star, implying that they are accompanied by substantial mass loss. Here, we present a semi-analytic model for SN precursor light curves, which we apply to constrain the properties and mechanisms of the pre-explosion mass loss. We explore two limiting mass-loss scenarios: (1) an "eruption" arising from shock breakout following impulsive energy deposition below the stellar surface; and (2) a steady "wind," due to sustained heating of the progenitor envelope. The eruption model, which resembles a scaled-down version of Type IIP SNe, can explain the luminosities and timescales of well-sampled precursors, for ejecta masses ~ 0.1-1 M ⊙ and velocities ~ 100-1000 km s-1. By contrast, the steady wind scenario cannot explain the highest precursor luminosities ≳ 1041 erg s-1, under the constraint that the total ejecta mass does not exceed the entire progenitor mass (though the less luminous SN 2020tlf precursor can be explained by a mass-loss rate ~ 1 M ⊙ yr-1). However, shock interaction between the wind and pre-existing (earlier ejected) CSM may boost its radiative efficiency and mitigate this constraint. In both the eruption and wind scenarios, the precursor ejecta forms compact (≲1015 cm) optically thick CSM at the time of core collapse; though only directly observable via rapid post-explosion spectroscopy (≲ a few days before being overtaken by the SN ejecta), this material can boost the SN luminosity via shock interaction.

Keywords: supernovae; core-collapse supernovae; stellar mass loss
A Wind-driven Model: Application to Peculiar Transients AT2018cow and iPTF14hls

We propose a wind-driven model for peculiar transients, and apply the model to AT2018cow and iPTF14hls. In the wind-driven model, we assume that a continuous outflow like a stellar wind is injected from a central system. While these transients have different observational properties, this model can explain their photometric properties which are not reproduced by a supernova-like instantaneous explosion. Furthermore, the model predicts characteristic spectral features and evolution, which are well in line with those of AT2018cow and iPTF14hls. Despite the different observational properties, the wind model shows that they have some common features; the large mass-loss rates (up to $\sim 20{M}_{\odot }\,{\mathrm{yr}}^{-1}$ for AT2018cow and $\sim 75{M}_{\odot }\,{\mathrm{yr}}^{-1}$ for iPTF14hls), and the characteristic radii of $\sim {10}^{13}\,\mathrm{cm}$ for the launch of the wind. It would indicate that both may be related to events involving a red supergiant (RSG), in which the RSG envelope is rapidly ejected by an event at a stellar core scale. On the other hand, the main differences are the kinetic energies, the total ejected mass, and the timescales. We then suggest that iPTF14hls may represent a dynamical common-envelope evolution induced by a massive binary system ( $\sim 120{M}_{\odot }+100{M}_{\odot }$ ). AT2018cow may be either a tidal disruption event of a low-mass RSG by a black hole (BH), or a BH-forming failed supernova.

Keywords: red supergiant stars; transient sources; stellar winds
Clarifying the Optical Thin-lens Equations of Gravitational Self-lensing

We exploit an analogy between gravitational lenses and optical lenses to determine the Gaussian form of the optical thin-lens equation of gravitational self-lensing (this is not the deflection-angle equation which is also called the "ray-tracing equation"). As in magnifying glasses, this Gaussian form determines the location of the virtual image in front of the lens and behind the source. Some confusion exists in the literature because a similar-looking equation of totally different substance is often written down, creating the false impression that this may be the equivalent optical lens equation. Although dimensionally correct and quite useful, this imitating form is misleading, as it masks a compound rate that should instead have always been visible. We clarify all related concepts, so that the readers will save themselves the unpleasant experience of reinterpreting/reclassifying the various self-lensing equations, including the new optical forms derived herein.

Keywords: black hole physics; compact binary stars; gravitational lensing; gravitational microlensing
Sagittarius B1: A Patchwork of H II Regions and Photodissociation Regions

Sgr B1 is a luminous H II region in the Galactic center immediately next to the massive star-forming giant molecular cloud Sgr B2 and apparently connected to it from their similar radial velocities. In 2018 we showed from SOFIA FIFI-LS observations of the [O III] 52 and 88 μm lines that there is no central exciting star cluster and that the ionizing stars must be widely spread throughout the region. Here we present SOFIA FIFI-LS observations of the [O I] 146 and [C II] 158 μm lines formed in the surrounding photodissociation regions (PDRs). We find that these lines correlate neither with each other nor with the [O III] lines although together they correlate better with the 70 μm Herschel PACS images from Hi-GAL. We infer from this that Sgr B1 consists of a number of smaller H II regions plus their associated PDRs, some seen face-on and the others seen more or less edge-on. We used the PDR Toolbox to estimate densities and the far-ultraviolet intensities exciting the PDRs. Using models computed with Cloudy, we demonstrate possible appearances of edge-on PDRs and show that the density difference between the PDR densities and the electron densities estimated from the [O III] line ratios is incompatible with pressure equilibrium unless there is a substantial pressure contribution from either turbulence or magnetic field or both. We also conclude that the hot stars exciting Sgr B1 are widely spaced throughout the region at substantial distances from the gas with no evidence of current massive star formation.

Keywords: galactic center; interstellar line emission; h ii regions; photodissociation regions
Sesquinary Catastrophe for Close-in Moons with Dynamically Excited Orbits

We identify a new mechanism that can lead to the destruction of small, close-in planetary satellites. If a small moon close to the planet has a sizable eccentricity and inclination, its ejecta that escape to the planetocentric orbit would often reimpact with much higher velocity due to the satellite's and fragment's orbits precessing out of alignment. If the impacts of returning ejecta result in net erosion, a runaway process can occur that may end in disruption of the satellite, and we term this process "sesquinary catastrophe." We expect the moon to reaccrete, but on an orbit with significantly lower eccentricity and inclination. We find that the large majority of small close-in moons in the solar system have orbits that are immune to sesquinary catastrophe. The exceptions include a number of resonant moonlets of Saturn for which resonances may affect the velocities of reimpact of their own debris. Additionally, we find that Neptune's moon Naiad (and to a lesser degree, Jupiter's Thebe) must have substantial internal strength, in line with prior estimates based on Roche limit stability. We also find that sesquinary instability puts important constraints on the plausible past orbits of Phobos and Deimos or their progenitors.

Keywords: natural satellite dynamics; natural satellites (solar system); collisional processes; natural satellite evolution
Detections of Dust in the Outskirts of M31 and M33

M31 and M33 serve as ideal places to study distributions of dust in the outskirts of spiral galaxies. In this Letter, using about 0.2 million stars selected from the LAMOST data and combining precise photometry and parallaxes from the Gaia DR2, we have constructed a two-dimensional foreground dust reddening map toward the M31 and M33 region (111°2 ≤ gl ≤ 136°2, -36°5 ≤ gb ≤ -16°5). The map has a typical spatial resolution of about 12' and precision of 0.01 mag. The complex structure of dust clouds toward M31 is revealed. By carefully removing the foreground extinction from the dust reddening map of Schlegel et al., we thus have obtained a residual map to study dust distributions in the outskirts of M31 and M33. A large amount of dust is detected in the M31 halo out to a distance of over 100 kpc. Dust in the M31 disk is found to extend out to about 2.5 times its optical radius, with a distribution that is consistent with either an exponential disk with a scale length of 7.2 kpc or two disks with a scale length of 11.1 kpc within its optical radius and 18.3 kpc beyond its optical radius. Dust in the disk of M33 is also found to extend out to about 2.5 times its optical radius, its distribution beyond one optical radius is consistent with an exponential disk with a scale length of 5.6 kpc. Our results provide new clues to the distributions and cycling of dust in galaxies.

Keywords: andromeda galaxy; circumgalactic medium; interstellar dust
Evryscope and K2 Constraints on TRAPPIST-1 Superflare Occurrence and Planetary Habitability

The nearby ultracool dwarf TRAPPIST-1 possesses several Earth-sized terrestrial planets, three of which have equilibrium temperatures that may support liquid surface water, making it a compelling target for exoplanet characterization. TRAPPIST-1 is an active star with frequent flaring, with implications for the habitability of its planets. Superflares (stellar flares whose energy exceeds 1033 erg) can completely destroy the atmospheres of a cool star's planets, allowing ultraviolet radiation and high-energy particles to bombard their surfaces. However, ultracool dwarfs emit little ultraviolet flux when quiescent, raising the possibility of frequent flares being necessary for prebiotic chemistry that requires ultraviolet light. We combine Evryscope and Kepler observations to characterize the high-energy flare rate of TRAPPIST-1. The Evryscope is an array of 22 small telescopes imaging the entire Southern sky in g' every two minutes. Evryscope observations, spanning 170 nights over 2 yr, complement the 80 day continuous short-cadence K2 observations by sampling TRAPPIST-1's long-term flare activity. We update TRAPPIST-1's superflare rate, finding a cumulative rate of ${4.2}_{-0.2}^{+1.9}$ superflares per year. We calculate the flare rate necessary to deplete ozone in the habitable-zone planets' atmospheres, and find that TRAPPIST-1's flare rate is insufficient to deplete ozone if present on its planets. In addition, we calculate the flare rate needed to provide enough ultraviolet flux to power prebiotic chemistry. We find TRAPPIST-1's flare rate is likely insufficient to catalyze some of the Earthlike chemical pathways thought to lead to ribonucleic acid synthesis, and flux due to flares in the biologically relevant UV-B band is orders of magnitude less for any TRAPPIST-1 planet than has been experienced by Earth at any time in its history.

Keywords: m dwarf stars; stellar flares; extrasolar rocky planets; exoplanets; red dwarf flare stars; flare stars; astrobiology; pre-biotic astrochemistry
Optical Forbidden Emission Line Spectro-astrometry of T CrA: Evidence for a Multiple System and Multiple Jets

Spectro-astrometry is applied to echelle spectra of the young intermediate-mass star T CrA. The aim is to better understand the origin of the [O I] and [S II] emission from T CrA and further explore the usefulness of spectro-astrometry in the search for a reliable tracer of MHD disk winds. The analysis reveals a small-scale curved jet in an east-west direction and inclined parallel to the plane of the sky. It is the inclination of this jet that led to the classification of the forbidden emission lines as a low-velocity component. Thus, spectro-astrometry highlights here that for close to edge-on disks spatial information is necessary. The position angle of the jet is not perpendicular to the position angle of the accretion disk nor does it agree with older observations of outflows likely driven by T CrA. The mass outflow rate of 5-10 × 10-8 M ⊙ yr-1 is within the range for intermediate-mass stars. We conclude that more than one outflow is driven by the T CrA system and that the curvature seen in the first detection of an outflow from T CrA and in the data presented here is likely due to the multiplicity of the system. * Based on data collected by UVES 089.C-0299(A) observations at the VLT on Cerro Paranal (Chile), which is operated by the European Southern Observatory (ESO).

Keywords: interstellar medium wind; star formation; stellar jets; stellar accretion disks
Fast Globally Optimal Catalog Matching using MIQCP

We propose a novel exact method to solve the probabilistic catalog matching problem faster than previously possible. Our new approach uses mixed integer programming and introduces quadratic constraints to shrink the problem by multiple orders of magnitude. We also provide a method to use a feasible solution to dramatically speed up our algorithm. This gain in performance is dependent on how close to optimal the feasible solution is. Also, we are able to provide good solutions by stopping our mixed integer programming solver early. Using simulated catalogs, we empirically show that our new mixed integer program with quadratic constraints is able to be set up and solved much faster than previous large linear formulations. We also demonstrate our new approach on real-world data from the Hubble Source Catalog. This paper is accompanied by publicly available software to demonstrate the proposed method.

Keywords: astronomical methods; catalogs; photometry; bayes factor
CEERS Key Paper. I. An Early Look into the First 500 Myr of Galaxy Formation with JWST

We present an investigation into the first 500 Myr of galaxy evolution from the Cosmic Evolution Early Release Science (CEERS) survey. CEERS, one of 13 JWST ERS programs, targets galaxy formation from z ~ 0.5 to >10 using several imaging and spectroscopic modes. We make use of the first epoch of CEERS NIRCam imaging, spanning 35.5 arcmin2, to search for candidate galaxies at z > 9. Following a detailed data reduction process implementing several custom steps to produce high-quality reduced images, we perform multiband photometry across seven NIRCam broad- and medium-band (and six Hubble broadband) filters focusing on robust colors and accurate total fluxes. We measure photometric redshifts and devise a robust set of selection criteria to identify a sample of 26 galaxy candidates at z ~ 9-16. These objects are compact with a median half-light radius of ~0.5 kpc. We present an early estimate of the z ~ 11 rest-frame ultraviolet (UV) luminosity function, finding that the number density of galaxies at M UV ~ -20 appears to evolve very little from z ~ 9 to 11. We also find that the abundance (surface density [arcmin-2]) of our candidates exceeds nearly all theoretical predictions. We explore potential implications, including that at z > 10, star formation may be dominated by top-heavy initial mass functions, which would result in an increased ratio of UV light per unit halo mass, though a complete lack of dust attenuation and/or changing star formation physics may also play a role. While spectroscopic confirmation of these sources is urgently required, our results suggest that the deeper views to come with JWST should yield prolific samples of ultrahigh-redshift galaxies with which to further explore these conclusions.

Keywords: early universe; galaxy formation; galaxy evolution; high-redshift galaxies
The Disk Population in a Distant Massive Protocluster

The unprecedented angular resolution and sensitivity of the Atacama Large Millimeter/submillimeter Array make it possible to unveil disk populations in distant (>2 kpc), embedded young cluster environments. We have conducted an observation toward the central region of the massive protocluster G286.21+0.16 at 1.3 mm. With a spatial resolution of 23 mas and a sensitivity of 15 μJy beam-1, we detect a total of 38 protostellar disks. These disks have dust masses ranging from about 53 to 1825 M ⊕, assuming a dust temperature of 20 K. This sample is not closely associated with previously identified dense cores, as would be expected for disks around Class 0 protostars. Thus, we expect our sample, being flux-limited, to be mainly composed of Class I/flat-spectrum source disks, since these are typically more massive than Class II disks. Furthermore, we find that the distributions of disk masses and radii are statistically indistinguishable from those of the Class I/flat-spectrum objects in the Orion molecular cloud, indicating that similar processes are operating in G286.21+0.16 to regulate disk formation and evolution. The cluster center appears to host a massive protostellar system composed of three sources within 1200 au, including a potential binary with 600 au projected separation. Relative to this center, there is no evidence for widespread mass segregation in the disk population. We do find a tentative trend of increasing disk radius versus distance from the cluster center, which may point to the influence of dynamical interactions being stronger in the central regions.

Keywords: protostars; young stellar objects; circumstellar disks; protoclusters
Identification of Lensed Gravitational Waves with Deep Learning

Similar to light, gravitational waves (GWs) can be lensed. Such lensing phenomena can magnify the waves, create multiple images observable as repeated events, and superpose several waveforms together, inducing potentially discernible patterns on the waves. In particular, when the lens is small, ≲105 M⊙, it can produce lensed images with time delays shorter than the typical gravitational-wave signal length that conspire together to form "beating patterns." We present a proof-of-principle study utilizing deep learning for identification of such a lensing signature. We bring the excellence of state-of-the-art deep learning models at recognizing foreground objects from background noise to identifying lensed GWs from noisy spectrograms. We assume the lens mass is around 103-105 M⊙, which can produce time delays of the order of milliseconds between two images of lensed GWs. We discuss the feasibility of distinguishing lensed GWs from unlensed ones and estimating physical and lensing parameters. The suggested method may be of interest to the study of more complicated lensing configurations for which we do not have accurate waveform templates.

Keywords: gravitational waves; weak gravitational lensing; astronomy data analysis; convolutional neural networks
(523599) 2003 RM: The Asteroid that Wanted to be a Comet

We report a statistically significant detection of nongravitational acceleration on the subkilometer near-Earth asteroid (523599) 2003 RM. Due to its orbit, 2003 RM experiences favorable observing apparitions every 5 yr. Thus, since its discovery, 2003 RM has been extensively tracked with ground-based optical facilities in 2003, 2008, 2013, and 2018. We find that the observed plane-of-sky positions cannot be explained with a purely gravity-driven trajectory. Including a transverse nongravitational acceleration allows us to match all observational data, but its magnitude is inconsistent with perturbations typical of asteroids such as the Yarkovsky effect or solar radiation pressure. After ruling out that the orbital deviations are due to a close approach or collision with another asteroid, we hypothesize that this anomalous acceleration is caused by unseen cometary outgassing. A detailed search for evidence of cometary activity with archival and deep observations from the Panoramic Survey Telescope and Rapid Response System and the Very Large Telescope does not reveal any detectable dust production. However, the best-fitting H2O sublimation model allows for brightening due to activity consistent with the scatter of the data. We estimate the production rate required for H2O outgassing to power the acceleration and find that, assuming a diameter of 300 m, 2003 RM would require Q(H2O) ~ 1023 molec s-1 at perihelion. We investigate the recent dynamical history of 2003 RM and find that the object most likely originated in the mid-to-outer main belt (~86% probability) as opposed to from the Jupiter-family comet region (~11% probability). Further observations, especially in the infrared, could shed light on the nature of this anomalous acceleration.

Keywords: asteroid dynamics; comet dynamics; near-earth objects
Study of the Cosmic Rays and Interstellar Medium in Local H I Clouds Using Fermi-LAT Gamma-Ray Observations

An accurate estimate of the interstellar gas density distribution is crucial to understanding the interstellar medium (ISM) and Galactic cosmic rays (CRs). To comprehend the ISM and CRs in a local environment, a study of the diffuse γ-ray emission in a midlatitude region of the third quadrant was performed. The γ-ray data in the 0.1-25.6 GeV energy range of the Fermi Large Area Telescope (LAT) and other interstellar gas tracers such as the HI4PI survey data and the Planck dust thermal emission model were used, and the northern and southern regions were analyzed separately. The variation of the dust emission ${D}_{\mathrm{em}}$ with the total neutral gas column density ${N}_{{\rm{H}}}$ was studied in high dust temperature areas, and the ${N}_{{\rm{H}}}$ / ${D}_{\mathrm{em}}$ ratio was calibrated using γ-ray data under the assumption of a uniform CR intensity in the studied regions. The measured integrated γ-ray emissivities above 100 MeV are $(1.58\pm 0.04)\times {10}^{-26}\,\mathrm{photons}\,{{\rm{s}}}^{-1}\,{\mathrm{sr}}^{-1}\,{\rm{H}} \mbox{-} {\mathrm{atom}}^{-1}$ and $(1.59\pm 0.02)\times {10}^{-26}\,\mathrm{photons}\,{{\rm{s}}}^{-1}\,{\mathrm{sr}}^{-1}\,{\rm{H}} \mbox{-} {\mathrm{atom}}^{-1}$ in the northern and southern regions, respectively, supporting the existence of a uniform CR intensity in the vicinity of the solar system. While most of the gas can be interpreted to be ${\rm{H}}\,{\rm{I}}$ with a spin temperature of ${T}_{{\rm{S}}}=125\,{\rm{K}}$ or higher, an area dominated by optically thick ${\rm{H}}\,{\rm{I}}$ with ${T}_{{\rm{S}}}\sim 40\,{\rm{K}}$ was identified.

Keywords: galactic cosmic rays; gamma-rays; interstellar medium