adsabs/SciX_UAT_keywords huggingface dataset:
Dense Gas Formation via Collision-induced Magnetic Reconnection in a Disk Galaxy with a Bisymmetric Spiral Magnetic Field

Recently, a collision-induced magnetic reconnection (CMR) mechanism was proposed to explain a dense filament formation in the Orion A giant molecular cloud. A natural question is whether CMR works elsewhere in the Galaxy. As an initial attempt to answer the question, this paper investigates the triggering of CMR and the production of dense gas in a flat-rotating disk with a modified Bisymmetric spiral (BSS) magnetic field. Cloud-cloud collisions at field reversals in the disk are modeled with the Athena++ code. Under the condition that is representative of the warm neutral medium, the cloud-cloud collision successfully triggers CMR at different disk radii. However, dense gas formation is hindered by the dominating thermal pressure, unless a moderately stronger initial field ≳5 μG is present. The strong-field model, having a larger Lundquist number S L and lower plasma β, activates the plasmoid instability in the collision midplane, which is otherwise suppressed by the disk rotation. We speculate that CMR can be common if more clouds collide along field reversals. However, to witness the CMR process in numerical simulations, we need to significantly resolve the collision midplane with a spatial dynamic range ≳106. If Milky Way spiral arms indeed coincide with field reversals in BSS, it is possible that CMR creates or maintains dense gas in the arms. High-resolution, high-sensitivity Zeeman/Faraday rotation observations are crucial for finding CMR candidates that have helical fields.

Keywords: star formation; milky way magnetic fields; molecular clouds; magnetic fields; interstellar medium; computational astronomy; astrophysical fluid dynamics; magnetohydrodynamical simulations; theoretical models; warm neutral medium; milky way disk; disk galaxies
Assessing the Detectability of Europa's Seafloor Topography from Europa Clipper's Gravity Data

Due to its size and tidal heating, Europa may potentially possess active volcanism and hydrothermal circulation at its seafloor. The upcoming Europa Clipper mission provides the opportunity to obtain global gravity maps over a range of spatial scales, up to degree l ≈ 10. We assess the ability of such gravity measurements to determine Europa's seafloor topography, building on and extending previous work in this area. We create a suite of models that test the gravity signature of a wider range of possible topographies and lithospheric thicknesses, spacecraft close-approach altitudes, and the effect of a gypsum layer on the seafloor. Additionally, we model Europa's seafloor scaled from other geologically active bodies, i.e., Earth, Venus, and Io, investigating the distinguishability of volcanic or plate tectonic features. We find that seafloor topography should be detectable at the resolution of Clipper, while the ice shell characteristics (e.g., via admittance analysis) are not resolvable globally. In our baseline scenario, seafloor topography dominates the total gravity signal up to degree l = 22, while for planetary analogs this proves true up to degree l = 11 for an Earth-scaled seafloor, as well as l = 42 and l = 54 for a Venus- or Io-scaled seafloor. Finally, we find that a putative layer of gypsum on the seafloor reduces the gravity signal by flattening out the seafloor, though its presence will not be detectable absent independent determination of its topographic amplitude.

Keywords: europa; galilean satellites; gravitational fields
Acceleration of Solar Wind Suprathermal Electrons at the Earth's Bow Shock

We present a statistical study of the in situ acceleration of solar wind suprathermal electrons at the Earth's bow shock, utilizing the Wind measurements in ambient solar wind and MMS1 measurements around the bow shock from 2015 September to 2017 December. All the selected 74 cases show significant suprathermal electron acceleration at the bow shock. The observed power-law indexes of accelerated electron energy spectra are significantly larger than the first-order Fermi acceleration prediction and the flux enhancement ratio peaks near a 90° pitch angle, suggesting that the shock drift acceleration (SDA) process plays a crucial role in accelerating suprathermal electrons at the bow shock. According to the observed electron spectral characteristics, the 74 cases can be classified into Types 1, 2, 3 and 4. The electron acceleration efficiency roughly increases from Type 1 to Type 4. For the Type 4 cases with strong electron acceleration, the shocked suprathermal electrons show a double-power-law energy spectrum bending downwards at a break near ~65 keV with a low-energy spectral index of ~3.1 and high-energy index of ~7.6. The observed break energy is comparable to a critical electron energy ${\varepsilon }_{\mathrm{ramp}}^{{dn}}$ with its cross-shock gyrodiameter equal to the shock's ramp thickness D ramp. At energies below (above) ${\varepsilon }_{\mathrm{ramp}}^{{dn}}$ , the accelerated electrons can be effectively confined into (can easily escape from) the SDA process with a roughly energy-independent (energy-decreasing) drift time and a probably conserved (nonadiabatically reduced) magnetic moment, since their gyrodiameter is less (greater) than D ramp. Therefore, such an SDA process could produce the observed double-power-law spectrum bending downwards at a break energy that is associated with D ramp.

Keywords: planetary bow shocks; interplanetary particle acceleration
The Solar System Notification Alert Processing System (SNAPS): Design, Architecture, and First Data Release (SNAPShot1)

We present here the design, architecture, and first data release for the Solar System Notification Alert Processing System (SNAPS). SNAPS is a solar system broker that ingests alert data from all-sky surveys. At present, we ingest data from the Zwicky Transient Facility (ZTF) public survey, and we will ingest data from the forthcoming Legacy Survey of Space and Time (LSST) when it comes online. SNAPS is an official LSST downstream broker. In this paper we present the SNAPS design goals and requirements. We describe the details of our automatic pipeline processing in which the physical properties of asteroids are derived. We present SNAPShot1, our first data release, which contains 5,458,459 observations of 31,693 asteroids observed by ZTF from 2018 July to 2020 May. By comparing a number of derived properties for this ensemble to previously published results for overlapping objects we show that our automatic processing is highly reliable. We present a short list of science results, among many that will be enabled by our SNAPS catalog: (1) we demonstrate that there are no known asteroids with very short periods and high amplitudes, which clearly indicates that in general asteroids in the size range 0.3-20 km are strengthless; (2) we find no difference in the period distributions of Jupiter Trojan asteroids, implying that the L4 and L5 clouds have different shape distributions; and (3) we highlight several individual asteroids of interest. Finally, we describe future work for SNAPS and our ability to operate at LSST scale.

Keywords: asteroids; small solar system bodies; sky surveys; catalogs
Characterization of Low-mass Companions to Kepler Objects of Interest Observed with APOGEE-N

We report the characterization of 28 low-mass (0.02 M ⊙ ≤ M 2 ≤ 0.25 M ⊙) companions to Kepler objects of interest (KOIs), eight of which were previously designated confirmed planets. These objects were detected as transiting companions to Sunlike stars (G and F dwarfs) by the Kepler mission and are confirmed as single-lined spectroscopic binaries in the current work using the northern multiplexed Apache Point Observatory Galactic Evolution Experiment near-infrared spectrograph (APOGEE-N) as part of the third and fourth Sloan Digital Sky Surveys. We have observed hundreds of KOIs using APOGEE-N and collected a total of 43,175 spectra with a median of 19 visits and a median baseline of ~1.9 yr per target. We jointly model the Kepler photometry and APOGEE-N radial velocities to derive fundamental parameters for this subset of 28 transiting companions. The radii for most of these low-mass companions are overinflated (by ~10%) when compared to theoretical models. Tidally locked M dwarfs on short-period orbits show the largest amount of inflation, but inflation is also evident for companions that are well separated from the host star. We demonstrate that APOGEE-N data provide reliable radial velocities when compared to precise high-resolution spectrographs that enable detailed characterization of individual systems and the inference of orbital elements for faint (H > 12) KOIs. The data from the entire APOGEE-KOI program are public and present an opportunity to characterize an extensive subset of the binary population observed by Kepler.

Keywords: binary stars; companion stars
Binary Stars in Upper Scorpius

To address the statistics of binary stars in the 8 Myr old Upper Scorpius (USco) star formation region, we conducted a speckle interferometric survey of 614 association members more massive than 0.4 {{ \mathcal M }}⊙ (spectral types earlier than M3V) based on the list of Luhman et al. (2018). We resolved 187 pairs, 55 of which are new discoveries. Also using the published data and the Gaia DR2, a catalog of 250 physical binaries was produced. We carefully estimated detection limits for each target and studied binary statistics in the separation range from 0.″06 to 20″ (9-2800 au), as well as clustering at larger separations. The frequency of companions with mass ratios q > 0.3 in this separation range is 0.33 ± 0.04 and 0.35 ± 0.04 for early M- and solar-type stars, respectively, larger by 1.62 ± 0.22 and 1.39 ± 0.18 times compared to field stars of similar masses. The excess is produced mostly by pairs closer than 100 au. At separations from 100 to 104 au, the separation distribution and companion fraction resemble those of solar-type stars in the field. However, unlike in the field, we see a relative deficit of equal-mass binaries at separations of ∼500 au, compared to smaller and larger separations. The distribution of q depends on the separation, with a preference of larger q and a larger fraction of twins with q > 0.95 at smaller separations. The binary population of USco differs from binaries in the field in several ways and suggests that binary statistics is not universal.

Keywords: binary stars; visual binary stars; multiple stars
Data-driven Uncertainty Quantification of the Wave Telescope Technique: General Equations and Demonstration Using HelioSwarm

The upcoming NASA mission HelioSwarm will use nine spacecraft to make the first simultaneous multipoint measurements of space plasmas spanning multiple scales. Using the wave telescope technique, HelioSwarm's measurements will allow for both the calculation of the power in wavevector and frequency space and the characterization of the associated dispersion relations of waves present in the plasma at MHD and ion-kinetic scales. This technique has been applied to the four-spacecraft Cluster and Magnetospheric Multiscale missions, and its effectiveness has previously been characterized in a handful of case studies. We expand this uncertainty quantification analysis to arbitrary configurations of four through nine spacecraft for three-dimensional plane waves. We use Bayesian inference to learn equations that approximate the error in reconstructing the wavevector as a function of relative wavevector magnitude, spacecraft configuration shape, and number of spacecraft. We demonstrate the application of these equations to data drawn from a nine-spacecraft configuration to both improve the accuracy of the technique, as well as expand the magnitudes of wavevectors that can be characterized.

Keywords: plasma physics; magnetic fields; bayesian statistics; computational methods; space plasmas
Multiband Probabilistic Cataloging: A Joint Fitting Approach to Point-source Detection and Deblending

Probabilistic cataloging (PCAT) outperforms traditional cataloging methods on single-band optical data in crowded fields. We extend our work to multiple bands, achieving greater sensitivity (∼0.4 mag) and greater speed (500×) compared to previous single-band results. We demonstrate the effectiveness of multiband PCAT on mock data, in terms of both recovering accurate posteriors in the catalog space and directly deblending sources. When applied to Sloan Digital Sky Survey (SDSS) observations of M2, taking Hubble Space Telescope data as truth, our joint fit on r- and i-band data goes ∼0.4 mag deeper than single-band probabilistic cataloging and has a false discovery rate less than 20% for F606W ≤ 20. Compared to DAOPHOT, the two-band SDSS catalog fit goes nearly 1.5 mag deeper using the same data and maintains a lower false discovery rate down to F606W ∼ 20.5. Given recent improvements in computational speed, multiband PCAT shows promise in application to large-scale surveys and is a plausible framework for joint analysis of multi-instrument observational data. https://github.com/RichardFeder/multiband_pcat.

Keywords: catalogs; star counts; sky surveys; globular star clusters; bayesian statistics; hierarchical models
Properties of Type Iax Supernova 2019muj in the Late Phase: Existence, Nature, and Origin of the Iron-rich Dense Core

Type Iax supernovae (SNe Iax) form a class of peculiar SNe Ia, whose early phase spectra share main spectral line identifications with canonical SNe Ia but with higher ionization and much lower line velocities. Their late-time behaviors deviate from usual SNe Ia in many respects; SNe Iax continue showing photospheric spectra over several 100 days and the luminosity decline is very slow. In this work, we study the late-time spectra of SN Iax 2019muj, including a newly presented spectrum at ~500 days. The spectrum is still dominated by allowed transitions but with a lower ionization state, with possible detection of [O I]λλ6300, 6363. By comprehensively examining the spectral formation processes of allowed transitions (Fe II, Fe I, and the Ca II near-IR triplet) and forbidden transitions ([Ca II]λλ7292, 7324 and [O I]), we quantitatively constrain the nature of the innermost region and find that it is distinct from the outer ejecta; the mass of the innermost component is ~0.03 M ⊙ dominated by Fe (which can initially be 56Ni), expanding with a velocity of ~760 km s-1. We argue that the nature of the inner component is explained by the failed/weak white-dwarf thermonuclear explosion scenario. We suggest that a fraction of the 56Ni-rich materials initially confined in (the envelope of) the bound remnant can later be ejected by the energy input through the 56Ni/Co/Fe decay, forming the second unbound ejecta component which manifests itself as the inner dense component seen in the late phase.

Keywords: type ia supernovae; transient sources; radiative processes; spectral line identification; white dwarf stars
Hunting for Neutrino Emission from Multifrequency Variable Sources

Pinpointing the neutrino sources is crucial to unveil the mystery of high-energy cosmic rays. The search for neutrino source candidates from coincident neutrino-photon signatures and objects with particular electromagnetic flaring behaviors can increase our chances of finding neutrino emitters. In this paper, we first study the temporal correlations of astrophysical flares with neutrinos, considering a few hundred multifrequency sources from the Atacama Large Millimeter/submillimeter Array, the Wide-field Infrared Survey Explorer (WISE), Swift, and Fermi in the containment regions of IceCube high-energy alerts. Furthermore, the spatial correlations between blazars and neutrinos are investigated using the subset of 10 yr IceCube track-like neutrinos with around 250,000 events. In a second test, we account for 2700 blazars with different types of flaring stages in addition to their position. No significant neutrino emissions were found from our analyses. Our results indicate an interesting trend showing that the infrared flaring phases of WISE blazars might be correlated with the arrival times of the neutrino alerts. A possible overflow of neutrinos associated with two of our selected blazar samples is discussed in detail. One is characterized by a significant flaring lag in infrared with respect to γ-rays, as seen for TXS 0506+056, and the other is characterized by highly simultaneous infrared and γ-ray flares. Our investigation suggests the need to improve current multifrequency light-curve catalogs to pair with the advent of more sensitive neutrino observatories.

Keywords: high energy astrophysics; active galactic nuclei; neutrino astronomy; blazars; light curves
Near-infrared Spectra of the Inflated Post-common Envelope Brown Dwarf NLTT 5306 B

NLTT 5306 is a post-common envelope binary made up of a white dwarf host and brown dwarf companion that has shown evidence of inflation and active mass donation despite not filling its Roche lobe. Two proposed mechanisms for the brown dwarf's inflation are magnetic interactions and a high-metallicity, cloudy atmosphere. We present moderate-resolution (R ≲ 2000) J-band Keck/NIRSPEC observations of this system. These phase-resolved data allow us to constrain differences between atmospheric parameters of the day- and nightside of the brown dwarf. Our day- and nightside effective temperature measurements are consistent, in agreement with the brightness temperatures measurements from Casewell et al. The dayside favors a slightly lower surface gravity, perhaps stemming from the material streaming between the two objects. Finally, our data show a preference for low-metallicity models. This would be expected from the system's old age, but provides direct evidence that a high-metallicity, cloudy brown dwarf atmosphere is not responsible for the witnessed inflation. These results strengthen the case for magnetic interactions leading to inflation of NLTT 5306 B.

Keywords: brown dwarfs; white dwarf stars; roche lobe; spectroscopy; common envelope evolution
An Aligned Orbit for the Young Planet V1298 Tau b

The alignment of planetary orbits with respect to the stellar rotation preserves information on their dynamical histories. Measuring this angle for young planets helps illuminate the mechanisms that create misaligned orbits for older planets, as different processes could operate over timescales ranging from a few megayears to a gigayear. We present spectroscopic transit observations of the young exoplanet V1298 Tau b; we update the age of V1298 Tau to be 28 ± 4 Myr based on Gaia EDR3 measurements. We observed a partial transit with Keck/HIRES and LBT/PEPSI, and detected the radial velocity anomaly due to the Rossiter-McLaughlin effect. V1298 Tau b has a prograde, well-aligned orbit, with $\lambda ={4}_{-10}^{+7}$ deg. By combining the spectroscopically measured $v\sin {i}_{\star }$ and the photometrically measured rotation period of the host star we also find that the orbit is aligned in 3D, $\psi ={8}_{-7}^{+4}$ deg. Finally, we combine our obliquity constraints with a previous measurement for the interior planet V1298 Tau c to constrain the mutual inclination between the two planets to be i mut = 0° ± 19°. This measurements adds to the growing number of well-aligned planets at young ages, hinting that misalignments may be generated over timescales of longer than tens of megayears. The number of measurements, however, is still small, and this population may not be representative of the older planets that have been observed to date. We also present the derivation of the relationship between i mut, λ, and i for the two planets.

Keywords: exoplanets; exoplanet dynamics; high resolution spectroscopy; starspots; pre-main sequence
Discovery of 22 GHz Water Masers in the Serpens South Region

Using the Karl G. Jansky Very Large Array (VLA), we have conducted a survey for 22 GHz, 61,6-52,3 H2O masers toward the Serpens South region. The masers were also observed with the Very Long Baseline Array following the VLA detections. We detect for the first time H2O masers in the Serpens South region that are found to be associated to three Class 0-Class I objects, including the two brightest protostars in the Serpens South cluster, known as CARMA-6 and CARMA-7. We also detect H2O masers associated to a source with no outflow or jet features. We suggest that this source is most probably a background asymptotic giant branch star projected in the direction of Serpens South. The spatial distribution of the emission spots suggest that the masers in the three Class 0-Class I objects emerge very close to the protostars and are likely excited in shocks driven by the interaction between a protostellar jet and the circumstellar material. Based on the comparison of the distributions of bolometric luminosity of sources hosting 22 GHz H2O masers and 162 young stellar objects covered by our observations, we identify a limit of LBol ≈ 10L⊙ for a source to host water masers. However, the maser emission shows strong variability in both intensity and velocity spread, and therefore masers associated to lower-luminosity sources may have been missed by our observations. We also report 11 new sources with radio continuum emission at 22 GHz.

Keywords: water masers; low mass stars; interferometers; protoclusters; young stellar objects; protostars
J115307.93+353528.2—Spectroscopic Twin Binary, Composed of Solar Like Stars. Orbital Solution from Poorly Resolved Double-line Structure

We present a study of double-lined spectroscopic binary (SB2) J115307.93+353528.2 based on data from the Large Sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) medium resolution survey (MRS). We use full-spectrum fitting to derive radial velocities and spectral parameters, which suggest that this is a "twin" system of two nearly identical stars, which are similar to the Sun. The orbital solution tells us that it is relatively wide pair of stars on slightly eccentric orbit with period P ≃ 206 days. This result shows that LAMOST-MRS data can be used to detect such twin binaries even when double-line structure is poorly resolved in the spectra. Changes of values from single star model analysis allows us to reliably select such SB2 candidate and to make first estimate of the orbital period.

Keywords: spectroscopic binary stars
Merger Signatures are Common, but not Universal, in Massive, Recently Quenched Galaxies at z 0.7

We present visual classifications of merger-induced tidal disturbances in 143 M * ~ 1011 M ⊙ post-starburst galaxies at z ~ 0.7 identified in the $\mathrm{SQuIGG}\vec{L}{\rm{E}}$ Sample. This sample spectroscopically selects galaxies from the Sloan Digital Sky Survey that have stopped their primary epoch of star formation within the past ~500 Myr. Visual classifications are performed on Hyper Suprime-Cam imaging. We compare to a control sample of mass- and redshift-matched star-forming and quiescent galaxies from the Large Early Galaxy Census and find that post-starburst galaxies are more likely to be classified as disturbed than either category. This corresponds to a factor of ${3.6}_{-1.3}^{+2.9}$ times the disturbance rate of older quiescent galaxies and ${2.1}_{-.73}^{+1.9}$ times the disturbance rate of star-forming galaxies. Assuming tidal features persist for ≲500 Myr, this suggests merging is coincident with quenching in a significant fraction of these post-starbursts. Galaxies with tidal disturbances are younger on average than undisturbed post-starburst galaxies in our sample, suggesting tidal features from a major merger may have faded over time. This may be exacerbated by the fact that, on average, the undisturbed subset is fainter, rendering low-surface-brightness tidal features harder to identify. However, the presence of 10 young (≲150 Myr since quenching) undisturbed galaxies suggests that major mergers are not the only fast physical mechanism that shut down the primary epoch of star formation in massive galaxies at intermediate redshift.

Keywords: post-starburst galaxies; galaxy quenching; galaxy evolution; quenched galaxies; galaxies; galaxy mergers