adsabs/SciX_UAT_keywords huggingface dataset:
A 3D View of Orion. I. Barnard's Loop

Barnard's Loop is a famous arc of Hα emission located in the Orion star-forming region. Here, we provide evidence of a possible formation mechanism for Barnard's Loop and compare our results with recent work suggesting a major feedback event occurred in the region around 6 Myr ago. We present a 3D model of the large-scale Orion region, indicating coherent, radial, 3D expansion of the OBP-Near/Briceño-1 (OBP-B1) cluster in the middle of a large dust cavity. The large-scale gas in the region also appears to be expanding from a central point, originally proposed to be Orion X. OBP-B1 appears to serve as another possible center, and we evaluate whether Orion X or OBP-B1 is more likely to have caused the expansion. We find that neither cluster served as the single expansion center, but rather a combination of feedback from both likely propelled the expansion. Recent 3D dust maps are used to characterize the 3D topology of the entire region, which shows Barnard's Loop's correspondence with a large dust cavity around the OPB-B1 cluster. The molecular clouds Orion A, Orion B, and Orion λ reside on the shell of this cavity. Simple estimates of gravitational effects from both stars and gas indicate that the expansion of this asymmetric cavity likely induced anisotropy in the kinematics of OBP-B1. We conclude that feedback from OBP-B1 has affected the structure of the Orion A, Orion B, and Orion λ molecular clouds and may have played a major role in the formation of Barnard's Loop.

Keywords: stellar feedback; dust shells; supernovae; star formation; star forming regions
Spectral Characterization of the Low-mass Companion μ Virgenes B

We report optical and near-infrared spectral characterization of an M dwarf companion to the bright F2 star μ Virgenes. Data from Shane/Kast and IRTF/SpeX yield identical spectral types of M5, and spectral features indicate solar metallicity ([Fe/H] = -0.05 ± 0.20) with no evidence of low surface gravity features at optical or near-infrared bands. Strong Hα emission ( ${\mathrm{log}}_{10}{L}_{{\rm{H}}\alpha }/{L}_{\mathrm{bol}}$ = -3.80 ± 0.09) is consistent with an active source at saturation, while the lack of Li I absorption and low surface gravity features constrains the system's age to ≳200 Myr. Both metallicity and age estimates of the companion are consistent with its primary. As a well-resolved companion to an exceptionally well-characterized bright star, μ Virgenes B serves as a useful benchmark at the transition between partially and fully convective stars.

Keywords: companion stars; m dwarf stars; solar neighborhood; stellar classification
Low-energy Electron-track Imaging for a Liquid Argon Time-projection-chamber Telescope Concept Using Probabilistic Deep Learning

The GammaTPC is an MeV-scale single-phase liquid argon time-projection-chamber gamma-ray telescope concept with a novel dual-scale pixel-based charge-readout system. It promises to enable a significant improvement in sensitivity to MeV-scale gamma rays over previous telescopes. The novel pixel-based charge readout allows for imaging of the tracks of electrons scattered by Compton interactions of incident gamma rays. The two primary contributors to the accuracy of a Compton telescope in reconstructing an incident gamma-ray's original direction are its energy and position resolution. In this work, we focus on using deep learning to optimize the reconstruction of the initial position and direction of electrons scattered in Compton interactions, including using probabilistic models to estimate predictive uncertainty. We show that the deep-learning models are able to predict locations of Compton scatters of MeV-scale gamma rays from simulated 500 μm pixel-based data to better than 1 mm rms error and are sensitive to the initial direction of the scattered electron. We compare and contrast different deep-learning uncertainty estimation algorithms for reconstruction applications. Additionally, we show that event-by-event estimates of the uncertainty of the locations of the Compton scatters can be used to select those events that were reconstructed most accurately, leading to improvement in locating the origin of gamma-ray sources on the sky.

Keywords: gamma-ray telescopes; gamma-ray transient sources; convolutional neural networks; gamma-ray detectors; astronomy image processing
Prospects from TESS and Gaia to Constrain the Flatness of Planetary Systems

The mutual inclination between planets orbiting the same star provides key information to understand the formation and evolution of multiplanet systems. In this work, we investigate the potential of Gaia astrometry in detecting and characterizing cold Jupiters in orbits exterior to the currently known Transiting Exoplanet Survey Satellite (TESS) planet candidates. According to our simulations, out of the ~3350 systems expected to have cold Jupiter companions, Gaia, by its nominal 5 yr mission, should be able to detect ~200 cold Jupiters and measure the orbital inclinations with a precision of ${\sigma }_{\cos i}\lt 0.2$ in ~120 of them. These numbers are estimated under the assumption that the orbital orientations of the CJs follow an isotropic distribution, but these only vary slightly for less broad distributions. We also discuss the prospects from radial velocity follow-ups to better constrain the derived properties and provide a package to do quick forecasts using our Fisher matrix analysis. Overall, our simulations show that Gaia astrometry of cold Jupiters orbiting stars with TESS planets can distinguish dynamically cold (mean mutual inclination ≲5°) from dynamically hot systems (mean mutual inclination ≳20°), placing a new set of constraints on their formation and evolution.

Keywords: exoplanets; extrasolar gaseous planets; exoplanet catalogs; space astrometry; exoplanet migration
Galactic Bar Resonances with Diffusion: An Analytic Model with Implications for Bar-Dark Matter Halo Dynamical Friction

The secular evolution of disk galaxies is largely driven by resonances between the orbits of "particles" (stars or dark matter) and the rotation of non-axisymmetric features (spiral arms or a bar). Such resonances may also explain kinematic and photometric features observed in the Milky Way and external galaxies. In simplified cases, these resonant interactions are well understood: for instance, the dynamics of a test particle trapped near a resonance of a steadily rotating bar is easily analyzed using the angle-action tools pioneered by Binney, Monari, and others. However, such treatments do not address the stochasticity and messiness inherent to real galaxies-effects that have, with few exceptions, been previously explored only with complex N-body simulations. In this paper, we propose a simple kinetic equation describing the distribution function of particles near an orbital resonance with a rigidly rotating bar, allowing for diffusion of the particles' slow actions. We solve this equation for various values of the dimensionless diffusion strength Δ, and then apply our theory to the calculation of bar-halo dynamical friction. For Δ = 0, we recover the classic result of Tremaine and Weinberg that friction ultimately vanishes, owing to the phase mixing of resonant orbits. However, for Δ > 0, we find that diffusion suppresses phase mixing, leading to a finite torque. Our results suggest that stochasticity-be it physical or numerical-tends to increase bar-halo friction, and that bars in cosmological simulations might experience significant artificial slowdown, even if the numerical two-body relaxation time is much longer than a Hubble time.

Keywords: galactic bar; barred spiral galaxies; galaxy dark matter halos; dynamical friction; orbital resonances; stellar kinematics; plasma physics
High-resolution Observations of Plume Footpoints in a Solar Coronal Hole

Plumes are bright structures in coronal holes extending from the solar surface into the corona and are considered as a possible source of the solar wind. Plumes are thought to be rooted in strong unipolar photospheric flux patches (network/plage region). The magnetic activities at the base of plumes may play a crucial role in producing outflows and propagating disturbances (PDs). However, the role of photospheric/chromospheric activities (e.g., jets/spicules) at the base of plumes and their connection to PDs is poorly understood. Using high-resolution observations of a plume taken on 2020 July 23 with the 1.6 m Goode Solar Telescope (GST), Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we analyzed chromospheric/transition region activities at the base of the plume and their connection to outflows/PDs in the plume. The GST Visible Imaging Spectrometer images reveal repetitive spicules with blueshifted emission (pseudo-Doppler maps) at the plume's footpoint. In addition, the photospheric magnetograms provide evidence of mixed polarities at the base of the plume. The IRIS Mg II k Dopplergrams show strong blueshifted emission (~50 km s-1) and a high brightness temperature (Mg II k2 line) at the footpoint of the plume. The long-period PDs (P ≈ 20-25 minutes) along the plume (AIA 171 Å) match the periodicity of spicules in the chromospheric images, suggesting a close connection between the spicules and the PDs. We suggest that the interchange reconnection between the closed and open flux of the coronal bright point at the plume's footpoint is the most likely candidate to produce upflows and associated PDs along the plume.

Keywords: solar coronal plumes
Time-variable Radio Recombination Line Emission in W49A

We present new Jansky Very Large Array (VLA) images of the central region of the W49A star-forming region at 3.6 cm and at 7 mm at resolutions of 0"15 (1650 au) and 0"04 (440 au), respectively. The 3.6 cm data reveal new morphological detail in the ultracompact H II region population, as well as several previously unknown and unresolved sources. In particular, source A shows elongated, edge-brightened bipolar lobes, indicative of a collimated outflow, and source E is resolved into three spherical components. We also present VLA observations of radio recombination lines at 3.6 cm and 7 mm, and IRAM Northern Extended Millimeter Array (NOEMA) observations at 1.2 mm. Three of the smallest ultracompact H II regions (sources A, B2, and G2) all show broad kinematic linewidths, with ΔVFWHM ≳ 40 km s-1. A multi-line analysis indicates that broad linewidths remain after correcting for pressure broadening effects, suggesting the presence of supersonic flows. Substantial changes in linewidth over the 21 yr time baseline at both 3.6 cm and 7 mm are found for source G2. At 3.6 cm, the linewidth of G2 changed from 31.7 ± 1.8 km s-1 to 55.6 ± 2.7 km s-1, an increase of +23.9 ± 3.4 km s-1. The G2 source was previously reported to have shown a 3.6 cm continuum flux density decrease of 40% between 1994 and 2015. This source sits near the center of a very young bipolar outflow whose variability may have produced these changes.

Keywords: compact h ii region; galactic radio sources
Surface Volatile Composition as Evidence for Hydrothermal Processes Lasting Longer in Triton's Interior than Pluto's

Ocean worlds, or icy bodies in the outer solar system that have or once had subsurface liquid water oceans, are among the most compelling topics of astrobiology. Typically, confirming the existence of a subsurface ocean requires close spacecraft observations. However, combining our understanding of the chemistry that takes place in a subsurface ocean with our knowledge of the building blocks that formed potential ocean worlds provides an opportunity to identify tracers of endogenic activity in the surface volatiles of Pluto and Triton. We show here that the current composition of the volatiles on the surfaces and in the atmospheres of Pluto and Triton are deficient in carbon, which can only be explained by the loss of CH4 through a combination of aqueous chemistry and atmospheric processes. Furthermore, we find that the relative nitrogen and water abundances are within the range observed in building block analogs, comets, and chondrites. A lower limit for N/Ar in Pluto's atmosphere also suggests source building blocks that have a cometary or chondritic composition, all pointing to an origin for their nitrogen as NH3 or organics. Triton's lower abundance of CH4 compared to Pluto, and the detection of CO2 at Triton but not at Pluto points to aqueous chemistry in a subsurface ocean that was more efficient at Triton than Pluto. These results have applications to other large Kuiper Belt objects as well as the assessment of formation locations and times for the four giant planets given future probe measurements of noble gas abundances and isotope ratios.

Keywords: solar system formation; planet formation; pluto; triton
Constraints on Primordial Non-Gaussianity Using the Multitracer Technique for Skew Spectra

Extracting the bispectrum information from large-scale structure observations is challenging due to the complex models and the computational costs involved in measuring the signal and its covariance. Recently, the skew spectrum was proposed to access parts of the bispectrum information in a more effective manner and was confirmed to provide complementary information to that available in power spectrum measurements. In this work, we generalize the theory to apply the multitracer technique and explore its ability to constrain the local-type primordial non-Gaussianity. Using the spectra and their covariance estimated from N-body simulations, we find that the multitracer approach is effective in reducing the cosmic variance noise. The 1σ marginalized errors for ${b}_{1}^{2}{A}_{s},{n}_{s}$, and ${f}_{\mathrm{NL}}^{\mathrm{loc}}$ are reduced by 50%, 52%, and 73% compared with the results achieved using only the power spectrum obtained from a single tracer. These results indicate that both the skew spectrum and the multitracer technique are useful in constraining the primordial non-Gaussianity with the forthcoming wide-field galaxy surveys.

Keywords: non-gaussianity; cosmological parameters from large-scale structure
Discovery of a Rare Late-type, Low-mass Wolf-Rayet Star in the LMC

We report the serendipitous discovery of an object, UVQS J060819.93-715737.4, with a spectrum dominated by extremely intense, narrow C II emission lines. The spectrum is similar to those of the very rare, late-type [WC11] low-mass Wolf-Rayet stars. Despite the recognition of these stars as a distinct class decades ago, there remains barely a handful of Galactic members, all of which are also planetary-nebula central stars. Although no obvious surrounding nebulosity is present in J0608, [O II], [N II], and [S II] emission suggest the presence of an inconspicuous, low-excitation nebula. There is low-amplitude incoherent photometric variability on timescales of days to years, as well as numerous prominent P Cygni profiles, implying mass loss. There are indications of a binary companion. The star is located on the outskirts of the LMC, and the observed radial velocity (∼+250 km s-1) and proper motion strongly suggest membership. If indeed an LMC member, this is the first extragalactic late [WC] star, and the first with an accurately determined luminosity, as the Galactic examples are too distant for precise parallax determinations. A high-quality, broad-coverage spectrum of the prototype of the late [WC] class, CPD -56° 8032, is also presented. We discuss different excitation mechanisms capable of producing the great strength of the C II emission. Numerous autoionizing levels of C II are definitely populated by processes other than dielectronic recombination. Despite the spectacular emission spectra, observational selection makes objects such as these difficult to discover. Members of the [WC11] class may in fact be considerably more common than the handful of previously known late [WC] stars.

Keywords: wc stars; planetary nebulae nuclei; planetary nebulae
Hidden Companions to Intermediate-mass Stars. VIII. Discovery of a 0.6 M ⊙, 1.7 au Companion to Albali = ϵ Aquarii

A large portion of the visually brightest stars in the night sky are late B to early A-type stars yet our knowledge of their multiplicity is incomplete. Here we report the discovery of a companion to the nearby star Albali (HIP 102618 = ϵ Aquarii), based on a VLTI/GRAVITY interferometric observation. The companion is at a projected separation ρ = 26 mas ↔ 1.7 au and has a K band flux ratio of 0.7%. Through isochrone fitting we find that Albali A is a 400 Myr old 2.8M ⊙ subgiant that has recently evolved off the main sequence, while the newly discovered Albali B is a 0.6 M ⊙ K dwarf. Further astrometric monitoring is needed in order to assess how strongly the stars are expected to interact as the primary expands. *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Keywords: multiple stars; a stars; b stars; optical interferometry
Gamma-Ray Burst Triangulation with a Near-Earth Network

We study the characteristics of near-Earth networks (NENs) of gamma-ray burst (GRB) detectors, with the objective of defining a network with all-sky, full-time localization capability for multimessenger astrophysics. We show that a minimum network consisting of nine identical spacecraft in two orbits with different inclinations provides a good combination of sky coverage with several-degree localization accuracy with detector areas of 100 cm2. In order to achieve this, careful attention must be paid to systematics. This includes accurate photon timing (∼0.1 ms), good energy resolution (∼10%), and reduction of Earth albedo, which are all within current capabilities. Such a network can be scaled in both the number and size of detectors to produce increased accuracy. We introduce a new method of localization that does not rely on on-board trigger systems or on the cross-correlation of time histories, but rather it tests positions in ground processing over the entire sky and assigns probabilities to them to detect and localize events. We demonstrate its capabilities with simulations. If the NEN spacecraft can downlink at least several hundred time- and energy-tagged events per second, and the data can be ground-processed as they are received, it can in principle derive GRB positions in near-real time over the entire sky.

Keywords: gamma-ray bursts; experimental techniques; gamma-ray detectors
Consistency Analysis of a Dark Matter Velocity-dependent Force as an Alternative to the Cosmological Constant

A range of cosmological observations demonstrate an accelerated expansion of the universe, and the most likely explanation of this phenomenon is a cosmological constant. Given the importance of understanding the underlying physics, it is relevant to investigate alternative models. This article uses numerical simulations to test the consistency of one such alternative model. Specifically, this model has no cosmological constant; instead, the dark matter particles have an extra force proportional to the velocity squared, somewhat reminiscent of the magnetic force in electrodynamics. The constant strength of the force is the only free parameter. Because bottom-up structure formation creates cosmological structures whose internal velocity dispersions increase in time, this model may mimic the temporal evolution of the effect from a cosmological constant. It is shown that models with force linearly proportional to internal velocities, or models proportional to velocity to power 3 or more, cannot mimic the accelerated expansion induced by a cosmological constant. However, models proportional to velocity squared are still consistent with the temporal evolution of a universe with a cosmological model.

Keywords: dark matter; cosmology; accelerating universe
Astromers: Nuclear Isomers in Astrophysics

We develop a method to compute thermally mediated transition rates between the ground state and long-lived isomers in nuclei. We also establish criteria delimiting a thermalization temperature above which a nucleus may be considered a single species and below which it must be treated as two separate species: a ground-state species and an astrophysical isomer ("astromer") species. Below the thermalization temperature, the destruction rates dominate the internal transition rates between the ground state and the isomer. If the destruction rates also differ greatly from one another, the nuclear levels fall out of or fail to reach thermal equilibrium. Without thermal equilibrium, there may not be a safe assumption about the distribution of occupation probability among the nuclear levels when computing nuclear reaction rates. In these conditions, the isomer has astrophysical consequences and should be treated as a separate astromer species which evolves separately from the ground state in a nucleosynthesis network. We apply our transition-rate methods and perform sensitivity studies on a few well-known astromers. We also study transitions in several other isomers of likely astrophysical interest. * This article is intended for unlimited release under LA-UR-20-22828.

Keywords: nucleosynthesis; stellar nucleosynthesis; s-process; r-process
Infrared Ejecta and Cold Dust in the Young Supernova Remnant N132D

We present Spitzer, Wide-field Infrared Survey Explorer (WISE), and Herschel observations of the young supernova remnant (SNR) N132D in the Large Magellanic Cloud, including 3-40 μm Spitzer Infrared Spectrograph (IRS) mapping, 12 μm WISE and 70, 100, 160, 250, 350, and 500 μm Herschel images. The high-velocity lines of [Ne II] at 12.8 μm, [Ne III] at 15.5 μm, and [O IV] 26 μm reveal infrared ejecta concentrated in a central ring and coincide with the optical and X-ray ejecta. Herschel images reveal far-IR emission coinciding with the central ejecta, which suggests that the IR emission is freshly formed, cold dust in the SN ejecta. The infrared spectra are remarkably similar to those of another young SNR of 1E0102 with Ne and O lines. Shock modeling of the Ne ejecta emission suggests a gas temperature of 300-600 K and densities in the range 1000-2 × 104 cm-3 in the postshock photoionized region. The IR continuum from the ejecta shows an 18 μm peak dust feature. We performed spectral fitting to the IRS dust continuum and Herschel photometry. The dust mass associated with the central ejecta is 1.25 ± 0.65 M ⊙, while the 18 μm dust feature requires forsterite grains. The dust mass of the central ejecta region in N132D is higher than those of other young SNRs, which is likely associated with its higher progenitor mass. We discuss the dust productivity in the ejecta of N132D and infer its plausible implications for dust in the early universe.

Keywords: dust continuum emission; core-collapse supernovae; type ib supernovae; early universe; supernova remnants; large magellanic cloud; origin of the universe; far infrared astronomy; interstellar emissions