adsabs/SciX_UAT_keywords huggingface dataset:
Topographically Influenced Evolution of Large-scale Changes in Comet 67P/Churyumov-Gerasimenko's Imhotep Region

Large portions of comet 67P/Churyumov-Gerasimenko's northern hemisphere are blanketed by fallback material consisting of centimeter-sized particles termed the smooth terrains. Observations from the Rosetta mission show that the most drastic transient changes during 67P's 2015 perihelion passage occurred within a subset of these deposits. However, we still do not understand the processes driving these changes, limiting our overall understanding of how comets evolve over both seasonal and multiorbit timescales. Herein we provide a complete documentation of scarp-driven activity on 67P's largest smooth terrain deposit, a highly active portion of the Imhotep region that is the southernmost of all smooth terrain basins on 67P. We also present a thermal model that accurately predicts when and where scarps originate during the course of the observed activity. Assuming a uniform surface composition, our model shows that activity is heavily controlled by local topography rather than the presence of ice-enhanced hot spots on the surface. Scarps within the smooth terrain deposits in central Imhotep also exhibit a peculiar behavior, where three scarps originate from the same location but at different times and migrate in opposite directions. This behavior indicates that the landscape retains a memory of previous cycles of erosion and deposition, reflected by the depth of the volatile-rich layer. Future work will need to couple our thermal model with a landscape evolution model in order to explain the complete dynamic evolution of these terrains.

Keywords: comet nuclei; small solar system bodies; comets
Minutes-delayed Jets from a Neutron Star Companion in Core-collapse Supernovae

This paper presents cases in which a neutron star (NS; or a black hole) companion to a type-Ib or type-Ic (stripped-envelope) core-collapse supernova (CCSN) accretes mass from the explosion ejecta and launches jets minutes to hours after explosion. The NS orbits at a pre-explosion radius of a ≃ 1-5 R⊙. When the ejecta velocity drops to ${v}_{\mathrm{ej}}\lesssim 1000\mbox{--}1500\,\mathrm{km}\,{{\rm{s}}}^{-1}$ , the ejecta gas that the NS accretes possesses sufficient specific angular momentum to form an accretion disk around the NS. The NS accretes a fraction of $({M}_{\mathrm{acc},{\rm{d}}}/{M}_{\mathrm{ej}})\approx 3\times {10}^{-5}\mbox{--}3\times {10}^{-4}$ of the ejecta mass through an accretion disk over a time period of ${t}_{{\rm{jets}}}\approx $ 10 minutes-few hr. If the jets carry about 10% of the accretion energy, then their total energy is a fraction of about 0.003-0.03 of the kinetic energy of the ejecta. The implications of these jets from an NS (or a black hole) companion to a CCSN are the shaping of the inner ejecta to have a bipolar morphology, energizing the light curve of the CCSN, and in some cases the possible enrichment of the inner ejecta with r-process elements.

Keywords: supernovae; type ib supernovae; neutron stars; stellar jets; common envelope binary stars; compact binary stars; high mass x-ray binary stars
Celestial Mechanics Leading up to the AAS Division on Dynamical Astronomy

This talk reviewed key developments leading to the establishment of the AAS Division on Dynamical Astronomy. In the 1890s, Simon Newcomb calculated astronomical constants and ephemerides for solar system bodies that were internationally adopted and used for 80 yr. The introduction of punch card equipment in the 1940s and computers in the 50s allowed much faster computations. Launches of Sputnik, Explorer, Vanguard, and Mercury satellites led to computing the orbits of satellites around the Earth and the field of astrodynamics. Dirk Brouwer's death in 1966 resulted in the celestial mechanics faculty at Yale spreading across the country. The space program, radar observations, and faster computers propelled advances in celestial mechanics. Teams at the Jet Propulsion Laboratory and Massachusetts Institute of Technology developed solar system ephemerides using numerical integrations fit to optical observations and radar ranging measurements. It was time for the AAS Division on Dynamical Astronomy.

Keywords: ephemerides; history of astronomy; orbit determination; astrodynamics
Formation of Quiescent Prominence Magnetic Fields by Supergranulations

To understand the formation of quiescent solar prominences, the origin of their magnetic field structures, i.e., magnetic flux ropes (MFRs), must be revealed. We use three-dimensional magnetofriction simulations in a spherical subdomain to investigate the role of typical supergranular motions in the long-term formation of a prominence magnetic field. Time-dependent horizontal supergranular motions with and without the effect of Coriolis force are simulated on the solar surface via Voronoi tessellation. The vortical motions by the Coriolis effect at boundaries of supergranules inject magnetic helicity into the corona. The helicity is transferred and accumulated along the polarity inversion line (PIL) as a strongly sheared magnetic field via helicity condensation. The diverging motions of supergranules converge opposite magnetic polarities at the PIL and drive the magnetic reconnection between footpoints of the sheared magnetic arcades to form an MFR. The magnetic network, negative-helicity MFR in the northern hemisphere, and fragmented-to-continuous formation process of magnetic dip regions are in agreement with observations. Although diverging supergranulations, differential rotation, and meridional flows are included, the simulation without the Coriolis effect cannot produce an MFR or sheared arcades to host a prominence. Therefore, Coriolis force is a key factor for helicity injection and the formation of magnetic structures of quiescent solar prominences.

Keywords: solar prominences; supergranulation; solar magnetic fields; magnetohydrodynamical simulations
TOI-1670 b and c: An Inner Sub-Neptune with an Outer Warm Jupiter Unlikely to Have Originated from High-eccentricity Migration

We report the discovery of two transiting planets around the bright (V = 9.9 mag) main-sequence F7 star TOI-1670 by the Transiting Exoplanet Survey Satellite. TOI-1670 b is a sub-Neptune ( ${R}_{{\rm{b}}}={2.06}_{-0.15}^{+0.19}$ R ⊕) on a 10.9 day orbit, and TOI-1670 c is a warm Jupiter ( ${R}_{{\rm{c}}}={0.987}_{-0.025}^{+0.025}$ R Jup) on a 40.7 day orbit. Using radial velocity observations gathered with the Tull Coudé Spectrograph on the Harlan J. Smith telescope and HARPS-N on the Telescopio Nazionale Galileo, we find a planet mass of ${M}_{{\rm{c}}}={0.63}_{-0.08}^{+0.09}$ M Jup for the outer warm Jupiter, implying a mean density of ${\rho }_{c}={0.81}_{-0.11}^{+0.13}$ g cm-3. The inner sub-Neptune is undetected in our radial velocity data (M b < 0.13 M Jup at the 99% confidence level). Multiplanet systems like TOI-1670 hosting an outer warm Jupiter on a nearly circular orbit ( ${e}_{{\rm{c}}}={0.09}_{-0.04}^{+0.05}$ ) and one or more inner coplanar planets are more consistent with "gentle" formation mechanisms such as disk migration or in situ formation rather than high-eccentricity migration. Of the 11 known systems with a warm Jupiter and a smaller inner companion, eight (73%) are near a low-order mean-motion resonance, which can be a signature of migration. TOI-1670 joins two other systems (27% of this subsample) with period commensurabilities greater than 3, a common feature of in situ formation or halted inward migration. TOI-1670 and the handful of similar systems support a diversity of formation pathways for warm Jupiters.

Keywords: exoplanet astronomy; radial velocity; exoplanet formation; transit photometry
Fermi-LAT Detection of GeV γ-Ray Emission from the Highly Asymmetric Shell Supernova Remnant SNR G317.3-0.A

In this paper, we report the first extended GeV γ-ray emission, at a significant level of ∼8.13σ, from the region of the supernova remnant SNR G317.3-0.2 by analyzing ∼12.2 yr of Fermi Large Area Telescope Pass 8 data in the work. The best-fit position of the new γ-ray source matches that of the 843 MHz radio energy band of SNR G317.3-0.2, and there is no significant variability of the photon flux of the corresponding light curve in the data for the 12.2 yr period. Therefore, by excluding other known γ-ray sources or candidates within a 2σ error radius from the best-fit position of SNR G317.3-0.2, we suggest that the γ-ray source is likely to be a GeV counterpart of SNR G317.3-0.2.

Keywords: gamma-ray astronomy; non-thermal radiation sources; supernova remnants; extended radiation sources
Protoplanetary Disk Size under Nonideal Magnetohydrodynamics: A General Formalism with Inclined Magnetic Field

Many mechanisms have been proposed to alleviate the magnetic catastrophe, which prevents the Keplerian disk from forming inside a collapsing magnetized core. Such propositions include inclined field and nonideal magnetohydrodynamics effects, and have been supported with numerical experiments. Models have been formulated for typical disk sizes when a field threads the rotating disk, parallel to the rotation axis, while observations at the core scales do not seem to show evident correlation between the directions of angular momentum and the magnetic field. In the present study, we propose a new model that considers both vertical and horizontal fields and discuss their effects on the protoplanetary disk size.

Keywords: protoplanetary disks; magnetohydrodynamics
Optimization of Magnetic Flux Ropes Modeled with the Regularized Biot-Savart Law Method

The so-called regularized Biot-Savart laws (RBSLs) provide an efficient and flexible method for modeling pre-eruptive magnetic configurations of coronal mass ejections (CMEs) whose characteristics are constrained by observational images and magnetic field data. This method allows one to calculate the field of magnetic flux ropes (MFRs) with small circular cross sections and an arbitrary axis shape. The field of the whole configuration is constructed as a superposition of (1) such a flux-rope field and (2) an ambient potential field derived, for example, from an observed magnetogram. The RBSL kernels are determined from the requirement that the MFR field for a straight cylinder must be exactly force free. For a curved MFR, however, the magnetic forces are generally unbalanced over the whole path of the MFR. To minimize these forces, we apply a modified Gauss-Newton method to find optimal MFR parameters. This is done by iteratively adjusting the MFR axis path and axial current. We then try to relax the resulting optimized configuration in a subsequent line-tied zero-beta magnetohydrodynamic simulation toward a force-free equilibrium. By considering two models of the sigmoidal pre-eruption configuration for the 2009 February 13 CME, we demonstrate how this approach works and what it is capable of. We show, in particular, that the building blocks of the core magnetic structure described by these models match morphological features typically observed in such types of configurations. Our method will be useful for both the modeling of particular eruptive events and theoretical studies of idealized pre-eruptive MFR configurations.

Keywords: solar coronal mass ejections; magnetohydrodynamical simulations; magnetohydrodynamics; solar active region magnetic fields; solar flares
PTFO 8-8695: Two Stars, Two Signals, No Planet

PTFO 8-8695 (CVSO 30) is a star in the 7-10 million year old Orion OB1a cluster that shows brightness dips that resemble planetary transits. Although strong evidence against the planet hypothesis has been presented, the possibility remains debated in the literature. To obtain further clues, we inspected data from the NASA Transiting Exoplanet Survey Satellite (TESS) and the ESA Gaia mission. The Gaia data suggest that PTFO 8-8695 is a binary: the photometric data show it to be overluminous with respect to members of its kinematic group, and the astrometric data are inconsistent with a single star. The TESS light curve shows two different photometric periods. The variability is dominated by a sinusoidal signal with a period of 11.98 hr, presumably caused by stellar rotation. Also present is a 10.76 hr signal consisting of a not-quite sinusoid interrupted by hour-long dips, the type of signal previously interpreted as planetary transits. The phase of the dips is nearly 180° away from the phase of the originally reported dips. As noted previously, this makes them difficult to explain as planetary transits. Instead, we believe that PTFO 8-8695 is a pair of young and rapidly rotating M dwarfs, one of which shows the same "transient-dipper" behavior that has been seen in at least five other cases. The origin of these transient dips is still unknown but likely involves circumstellar material.

Keywords: exoplanet evolution; pre-main sequence stars; stellar rotation; variable stars; low mass stars
Reproduction Experiments of Radial Pyroxene Chondrules Using a Gas-jet Levitation System under Reduced Conditions

Reproduction experiments of radial pyroxene (RP) chondrules were carried out using an Ar-H2 or Ar gas-jet levitation system in a reducing atmosphere in order to simulate chondrule formation in the protoplanetary disk. The experiments reproduced RP-chondrule textures, consisting of sets of thin pyroxene crystals and mesostasis glass between crystals. However, iron partition coefficients between pyroxene and glassy mesostasis (DFe =Fe mol%pyroxene/Fe mol%mesostasis) in natural RP chondrules were much higher than that in the experimentally reproduced RP chondrules. The high DFe in natural RP chondrules suggests that iron was removed from the mesostasis melt at high temperatures after the growth of pyroxene crystals. We found that many small iron-metal inclusions had formed in the mesostasis glass, indicating that FeO in the high-temperature melt of mesostasis was reduced to metallic iron, and iron in the mesostasis diffused into the newly formed metal inclusions. The formation of the iron-metal inclusions in the mesostasis was reproduced by our experiments in a reducing atmosphere, confirming that DFe in natural RP chondrules increased after the growth of RP crystals. Therefore, the DFe of RP chondrules can be an indicator to constrain cooling rates and redox states during chondrule formation.

Keywords: chondrules; chondrites; experimental techniques; protoplanetary disks
Updated High-temperature Opacities for the Dartmouth Stellar Evolution Program and Their Effect on the Jao Gap Location

The Jao Gap, a 17% decrease in stellar density at M G ~ 10 identified in both Gaia Data Release 2 and Early Data Release 3, presents a new method to probe the interior structure of stars near the fully convective transition mass. The Gap is believed to originate from convective-kissing instability wherein asymmetric production of 3He causes the core convective zone of a star to periodically expand and contract and consequently causes the star luminosities to vary. Modeling of the Gap has revealed a sensitivity in its magnitude to a population metallicity primarily through opacity. Thus far, models of the Jao Gap have relied on OPAL high-temperature radiative opacities. Here we present updated synthetic population models tracing the Gap location modeled with the Dartmouth stellar evolution code using the OPLIB high-temperature radiative opacities. Use of these updated opacities changes the predicted location of the Jao Gap by ~0.05 mag as compared to models that use the OPAL opacities. This difference is likely too small to be detectable in empirical data.

Keywords: stellar evolution; stellar evolutionary models
ALMA ACA and Nobeyama Observations of Two Orion Cores in Deuterated Molecular Lines

We mapped two molecular cloud cores in the Orion A cloud with the 7 m Array of the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeterArray (ALMA) and with the Nobeyama 45 m radio telescope. These cores have bright N2D+ emission in single-pointing observations with the Nobeyama 45 m radio telescope, have a relatively high deuterium fraction, and are thought to be close to the onset of star formation. One is a star-forming core, and the other is starless. These cores are located along filaments observed in N2H+ and show narrow line widths of 0.41 km s-1 and 0.45 km s-1 in N2D+, respectively, with the Nobeyama 45 m telescope. Both cores were detected with the ALMA ACA 7 m Array in the continuum and molecular lines at Band 6. The starless core G211 shows a clumpy structure with several sub-cores, which in turn show chemical differences. Also, the sub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular, shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting spatial feature of two N2D+ peaks of similar intensity and radial velocity located symmetrically with respect to the single dust continuum peak. One interpretation is that the two N2D+ peaks represent an edge-on pseudo-disk. The CO outflow lobes, however, are not directed perpendicular to the line connecting both N2D+ peaks.

Keywords: star forming regions; astrochemistry; interstellar medium; giant molecular clouds; molecular clouds; collapsing clouds
The Formation of Glycolonitrile (HOCH2CN) from Reactions of C+ with HCN and HNC on Icy Grain Mantles

Quantum chemical cluster calculations show that reactions of C+ with HCN or HNC embedded in the surface of an icy grain mantle can account for the formation of a recently detected molecule, glycolonitrile, which is considered to be an important precursor to ribonucleic compounds. Reactions of cations deposited on ice mantles with minimal kinetic energy have been found theoretically to result in previously unknown pathways to significant organic compounds in protostellar systems and the interstellar medium. In density functional theory cluster calculations involving up to 24H2O, C+ reacts consistently with HCN embedded in ice to yield the neutral HOCHNC radical with no barrier, along with H3O+ as a byproduct. If HOCHNC then reacts with H, three species can be formed: HOCH2NC (isocyanomethanol), HOCH2CN (glycolonitrile), and HOCHNCH. For the C++ HNC reaction on ice, the HOCHCN and H2OCCN radicals form as intermediates, the first of which is another direct precursor to glycolonitrile via H addition. In addition to characterizing reaction pathways, predictions are provided of the vibrational and electronic spectra of the HCN and HNC starting clusters and the HOCHNC ice-bound intermediate.

Keywords: astrochemistry; protoplanetary disks; protoplanetary nebulae; molecule formation; molecular spectroscopy; theoretical models; interstellar dust
Revisiting BD-06 1339b: A Likely False Positive Caused by Stellar Activity

As long as astronomers have searched for exoplanets, the intrinsic variability of host stars has interfered with the ability to reliably detect and confirm exoplanets. One particular source of false positives is the presence of stellar magnetic or chromospheric activity that can mimic the radial velocity reflex motion of a planet. Here we present the results of a photometric data analysis for the known planet-hosting star BD -06°1339, observed by the Transiting Exoplanet Survey Satellite during Sector 6 at a cadence of 2 minutes. We discuss evidence that suggests that the observed 3.9-day periodic radial velocity signature may be caused by stellar activity rather than a planetary companion, since variability detected in the photometric data is consistent with the periodic signal. We conclude that the previously reported planetary signature is likely the result of a false-positive signal resulting from stellar activity, and we discuss the need for more data to confirm this conclusion.

Keywords: exoplanet detection methods; exoplanet astronomy; stellar activity; stellar photometry; stellar rotation; radial velocity; exoplanets
Seismic Signatures of the 12C(α, γ)16O Reaction Rate in White Dwarf Models with Overshooting

We consider the combined effects that overshooting and the 12C(α, γ)16O reaction rate have on variable white dwarf (WD) stellar models. We find that carbon-oxygen (CO) WD models continue to yield pulsation signatures of the current experimental 12C(α, γ)16O reaction rate probability distribution function when overshooting is included in the evolution. These signatures hold because the resonating mantle region, encompassing ≃0.2 M ⊙ in a typical ≃0.6 M ⊙ WD model, still undergoes radiative helium burning during the evolution to a WD. Our specific models show two potential low-order adiabatic g-modes, g 2 and g 6, that signalize the 12C(α, γ)16O reaction rate probability distribution function. Both g-mode signatures induce average relative period shifts of ΔP/P = 0.44% and ΔP/P = 1.33% for g 2 and g 6, respectively. We find that g 6 is a trapped mode, and the g 2 period signature is inversely proportional to the 12C(α, γ)16O reaction rate. The g 6 period signature generally separates the slower and faster reaction rates, and has a maximum relative period shift of ΔP/P = 3.45%. We conclude that low-order g-mode periods from CO WDs may still serve as viable probes for the 12C(α, γ)16O reaction rate probability distribution function when overshooting is included in the evolution.

Keywords: asteroseismology; nuclear astrophysics; white dwarf stars; stellar physics
Recovery and Classification of Spherules from the Pacific Ocean Site of the CNEOS 2014 January 8 (IM1) Bolide

We have conducted an extensive towed-magnetic-sled survey during the period 2023 June 14–28, over the seafloor about 85 km north of Manus Island, Papua New Guinea, centered around the calculated path of the bolide CNEOS 2014 January 8 (IM1). We found about 850 spherules of diameter 0.05–1.3 mm in our samples. They were analyzed by microXRF, Electron Probe Microanalyzer and ICP Mass spectrometry. We identified 22% of the spherules as the product of planetary igneous differentiation and labeled them as D-type spherules. A small portion of the D-spherules show an excess of Be, La and U, by up to three orders of magnitude relative to the solar system standard of CI chondrites, and a composition pattern that is distinctly different from coal fly ash.

Keywords: meteors
Kinematics and Feedback in H II Regions in the Dwarf Starburst Galaxy IC 10

We present a survey of the central region of the nearest starburst galaxy, IC 10, using the W. M. Keck Observatory Keck Cosmic Web Imager (KCWI) at high spectral and spatial resolution. We map the central starburst of IC 10 to sample the kinematic and ionization properties of the individual star-forming regions. Using the low spectral resolution mode of KCWI, we map the oxygen abundance, and with the high spectral resolution mode, we identify 46 individual H II regions. These H II regions have an average radius of 4.0 pc, star formation rate ~1.3 × 10-4 M ⊙ yr-1, and velocity dispersion ~16 km s-1. None of the H II regions appear to be virialized (α vir ≫ 1), and on average, they show evidence of ongoing expansion. IC 10's H II regions are offset from the star-forming-region size-luminosity scaling relationships, as well as Larson's Law that relates size and velocity dispersion. We investigate the balance of inward and outward pressure, P in and P out, finding P out > P in in 89% of H II regions, indicating feedback-driven expansion even in these low-mass H II regions. We find warm gas pressure (P gas) provides the dominant contribution to the outward pressure (P out). This counteracts the inward pressure, which is dominated by turbulence in the surrounding gas rather than self-gravity. Five H II regions show evidence of outflows that are most likely supported by either stellar winds (two regions) or champagne flows (three regions). These observations provide new insights into the state of the star-forming regions in IC 10 and negative feedback from low-mass clusters.

Keywords: starburst galaxies; star forming regions; h ii regions; galaxy kinematics; galaxy dynamics; spectroscopy; dwarf irregular galaxies; ground-based astronomy; scaling relations