adsabs/SciX_UAT_keywords huggingface dataset:
CO Gas and Dust Outbursts from Centaur 29P/Schwassmann-Wachmann

29P/Schwassmann-Wachmann is an unusual solar system object. Originally classified as a short-period comet, it is now known as a Centaur that recently transferred to its current orbit, and may become a Jupiter family comet. It has exhibited a dust coma for over 90 yr, and regularly undergoes significant dust outbursts. Carbon monoxide is routinely detected in high amounts and is typically assumed to play a large role in generating the quiescent dust coma and outbursts. To test this hypothesis, we completed two three-month-long observing campaigns of the CO J = 2-1 rotational line using the Arizona Radio Observatory 10 m Submillimeter Telescope during 2016 and 2018-2019, and compared the results to visible magnitudes obtained at the same time. As the Centaur approached its 2019 perihelion, the quiescent dust coma grew ∼45% in brightness, while it is unclear whether the quiescent CO production rate also increased. A doubling of the CO production rate on 2016 February 28.6 UT did not trigger an outburst nor a rise in dust production for at least 10 days. Similarly, two dust outbursts occurred in 2018 while CO production continued at quiescent rates. Two other dust outbursts may show gas involvement. The data indicate that CO and dust outbursts are not always well correlated. This may be explained if CO is not always substantially incorporated with the dust component in the nucleus, or if CO is primarily released through a porous material. Additionally, other minor volatiles or physical processes may help generate dust outbursts.

Keywords: centaur group; comets; small solar system bodies; short period comets
Cosmic Rays Self-arising Turbulence with Universal Spectrum -8/3

In the inertial subrange of scales, an exact compressible turbulence universal spectrum law -8/3 for the density fluctuations of cosmic rays (CRs) in the frame of the known two-fluid model of CR dynamics is obtained. It is shown that the origin of this scaling law may be due to the arising of shocks at the breaking of the nonlinear simple waves of CRs near the scale of their Larmor's radii, as it is well known for the solar wind with the same turbulent spectrum law -8/3. The consistency of the turbulence spectrum -8/3 of CRs with the observed nonthermal differential energy distribution of CRs with a similar index -8/3 due to the possibility of self-reacceleration of the CRs on the self-arising shocks is stated. The turbulent diffusion mechanism for the observed CRs energy spectrum breaks is considered.

Keywords: cosmic rays; particle astrophysics; interplanetary turbulence; ultra-high-energy cosmic radiation; spectral energy distribution; interplanetary shocks
The Surprisingly Low Carbon Mass in the Debris Disk around HD 32297

Gas has been detected in a number of debris disks. It is likely secondary, I.e., produced by colliding solids. Here, we report ALMA Band 8 observations of neutral carbon in the CO-rich debris disk around the 15-30 Myr old A-type star HD 32297. We find that C0 is located in a ring at ∼110 au with an FWHM of ∼80 au and has a mass of (3.5 ± 0.2) × 10-3 M⊕. Naively, such a surprisingly small mass can be accumulated from CO photodissociation in a time as short as ∼104 yr. We develop a simple model for gas production and destruction in this system, properly accounting for CO self-shielding and shielding by neutral carbon, and introducing a removal mechanism for carbon gas. We find that the most likely scenario to explain both C0 and CO observations is one where the carbon gas is rapidly removed on a timescale of order a thousand years and the system maintains a very high CO production rate of ∼15 M⊕ Myr-1, much higher than the rate of dust grind-down. We propose a possible scenario to meet these peculiar conditions: the capture of carbon onto dust grains, followed by rapid CO re-formation and rerelease. In steady state, CO would continuously be recycled, producing a CO-rich gas ring that shows no appreciable spreading over time. This picture might be extended to explain other gas-rich debris disks.

Keywords: exoplanet formation; submillimeter astronomy; radio interferometry; atomic spectroscopy; debris disks; circumstellar gas
Temporal Variations of the Three Geomagnetic Field Components at Colaba Observatory around the Carrington Storm in 1859

The Carrington storm in 1859 September has been arguably identified as the greatest geomagnetic storm ever recorded. However, its exact magnitude and chronology remain controversial, while their source data have been derived from the Colaba H magnetometer in India. Here, we have located the Colaba 1859 yearbook, containing hourly measurements and spot measurements. We have reconstructed the Colaba geomagnetic disturbances in the horizontal component (ΔH), the eastward component (ΔY), and the vertical component (ΔZ) around the time of the Carrington storm. On their basis, we have chronologically revised the interplanetary coronal mass ejection transit time as ≤17.1 hr and located the ΔH peak at 06:20-06:25 UT, revealing a magnitude discrepancy between the hourly and spot measurements (-1691 nT versus -1263 nT). Furthermore, we have newly derived the time series of ΔY and ΔZ, which peaked at ΔY ≈ 378 nT (05:50 UT) and 377 nT (06:25 UT), and ΔZ ≈ -173 nT (06:40 UT). We have also computed their hourly averages and removed their solar quiet field variations in each geomagnetic component to derive their hourly disturbance variations (Dist) with latitudinal weighting. Our calculations have resulted in disturbance variations with latitudinal weighting of Dist Y ≈ 328 nT and Dist Z ≈ -36 nT, and three scenarios of Dist H ≈ -918, -979, and -949 nT, which also approximate the minimum Dst. These data may suggest preconditioning of the geomagnetic field after the August storm (ΔH ≤ -570 nT), which made the September storm even more geoeffective.

Keywords: solar coronal mass ejections; geomagnetic fields; space weather; solar-terrestrial interactions
[N I] 10400/10410 Å Lines as Possible Disk Wind Tracers in a Young Intermediate-mass Star

In this study, we performed high-resolution near-infrared (NIR) spectroscopy (R = 28,000; λ = 0.90–1.35 μm) with a high signal-to-noise ratio on HD 200775, a very young (∼0.1 Myr old) and massive intermediate-mass star (a binary star with a mass of about 10 M ⊙ each) with a protoplanetary disk. The obtained spectra show eight forbidden lines of three elements: two of [S II] (10289 and 10323 Å), two of [N I] (10400 and 10410 Å), and four of [Fe II] (12570, 12946, 12981, and 13209 Å). This is the first time that the [N I] lines are detected in a young stellar object with a doublet deblended. Gaussian fitting of the spectra indicates that all line profiles have low-velocity components and exhibit blueshifted features, suggesting that all lines originate from the disk winds (magnetohydrodynamic disk wind and/or photoevaporative wind). Based on the fit, the [N I] and [Fe II] lines are categorized into narrow components, while the [S II] lines are at the boundary between broad and narrow components. These forbidden lines are suggested to be very promising disk wind tracers among the existing ones because they are in the NIR-wavelength range, which can be observed from early stages with high sensitivities. Among these lines, [N I] lines would be a rather powerful probe for deriving the basic physical parameters of disk wind gases. However, the study of these lines herein is limited to one object; thus, further studies are needed to examine their properties.

Keywords: protoplanetary disks; stellar winds; star formation; herbig ae/be stars; t tauri stars; pre-main sequence stars; near infrared astronomy; high resolution spectroscopy
In Situ Observations of the Formation of Periodic Collisionless Plasma Shocks from Fast Mode Waves

It has been long theorized, but not directly observed, that low-frequency magnetosonic plasma waves can steepen and form shocks. We show an example of small-amplitude, sinusoidal magnetosonic waves at the proton gyrofrequency upstream of the Martian bow shock. We hypothesize that these waves are produced by an ion beam instability associated with the ionization of hydrogen atoms by charge exchange with solar wind protons, solar photoionization, and/or electron impact ionization. As the waves are convected toward the planet by solar wind flow, the wave amplitude grows due to additional free energy put into the system by further ion beam particles. Finally, the steepened waves form shocks. Because of their development, the shocks are periodic with the separation at the proton gyroperiod. These observations lead to the conclusion that newborn ions may play a crucial role in the formation process of some collisionless plasma shocks in astrophysical and space plasmas.

Keywords: shocks; pickup ions; plasma physics
On the Probability That a Rocky Planet's Composition Reflects Its Host Star

The bulk density of a planet, as measured by mass and radius, is a result of planet structure and composition. Relative proportions of iron core, rocky mantle, and gaseous envelopes are degenerate for a given density. This degeneracy is reduced for rocky planets without significant gaseous envelopes when the structure is assumed to be a differentiated iron core and rocky mantle, in which the core mass fraction (CMF) is a first-order description of a planet's bulk composition. A rocky planet's CMF may be derived both from bulk density and by assuming the planet reflects the host star's major rock-building elemental abundances (Fe, Mg, and Si). Contrasting CMF measures, therefore, shed light on the outcome diversity of planet formation from processes including mantle stripping, out-gassing, and/or late-stage volatile delivery. We present a statistically rigorous analysis of the consistency of these two CMF measures accounting for observational uncertainties of planet mass and radius and host-star chemical abundances. We find that these two measures are unlikely to be resolvable as statistically different unless the bulk density CMF is at least 40% greater than or 50% less than the CMF as inferred from the host star. Applied to 11 probable rocky exoplanets, Kepler-107 c has a CMF as inferred from bulk density that is significantly greater than the inferred CMF from its host star (2σ) and is therefore likely an iron-enriched super-Mercury. K2-229b, previously described as a super-Mercury, however, does not meet the threshold for a super-Mercury at a 1σ or 2σ level.

Keywords: exoplanets; extrasolar rocky planets; planetary interior; super earths
TOI-1075 b: A Dense, Massive, Ultra-short-period Hot Super-Earth Straddling the Radius Gap

Populating the exoplanet mass-radius diagram in order to identify the underlying relationship that governs planet composition is driving an interdisciplinary effort within the exoplanet community. The discovery of hot super-Earths-a high-temperature, short-period subset of the super-Earth planet population-has presented many unresolved questions concerning the formation, evolution, and composition of rocky planets. We report the discovery of a transiting, ultra-short-period hot super-Earth orbiting TOI-1075 (TIC351601843), a nearby (d = 61.4 pc) late-K/early-M-dwarf star, using data from the Transiting Exoplanet Survey Satellite. The newly discovered planet has a radius of 1.791 ${}_{-0.081}^{+0.116}$ R ⊕ and an orbital period of 0.605 day (14.5 hr). We precisely measure the planet mass to be 9.95 ${}_{-1.30}^{+1.36}$ M ⊕ using radial velocity measurements obtained with the Planet Finder Spectrograph mounted on the Magellan II telescope. Our radial velocity data also show a long-term trend, suggesting an additional planet in the system. While TOI-1075 b is expected to have a substantial H/He atmosphere given its size relative to the radius gap, its high density ( ${9.32}_{-1.85}^{+2.05}$ g cm-3) is likely inconsistent with this possibility. We explore TOI-1075 b's location relative to the M-dwarf radius valley, evaluate the planet's prospects for atmospheric characterization, and discuss potential planet formation mechanisms. Studying the TOI-1075 system in the broader context of ultra-short-period planetary systems is necessary for testing planet formation and evolution theories and density-enhancing mechanisms and for future atmospheric and surface characterization studies via emission spectroscopy with the JWST.

Keywords: exoplanets; extrasolar rocky planets; super earths; radial velocity; transit photometry; planetary system formation
Radial Migration from the Metallicity Gradient of Open Clusters and Outliers

Radial migration is an important process in the evolution of the Galactic disk. The metallicity gradient of open clusters and its outliers provide an effective way to examine this process. In this work, we compile metallicity, age, and kinematic parameters for 225 open clusters and carry out a quantitative analysis of radial migration via the calculated migration distances. Based on clusters with age <0.5 Gyr, we obtain a present-day metallicity gradient of -0.074 ± 0.007 dex kpc-1. Three sequences are distributed along this gradient, and clusters in the upper, middle, and lower groups are found to be old outward migrators, in situ clusters, and inward migrators, respectively. The migration distance increases with age, but the time when it is most effective is probably less than 3 Gyr. The metallicity gradient breaks at guiding center radius Rg ~ 11.5 kpc, which is caused by the lack of young open clusters in the outer disk and the presence of old outward migrators in the upper sequence. This shows that this boundary is related to the different effects of radial migration between the inner and outer disks. We also found many special open clusters in and near the outer disk with R > 11 kpc and a steeper metallicity gradient from the inner disk of Rg < 7 kpc, which tells of a complicated evolution history of the Galactic disk caused by different effects of stellar radial migration.

Keywords: galaxy disks; galaxy evolution; galaxy abundances; solar neighborhood; open star clusters; stellar kinematics
The Road to an Archival Data Format-Data Structures

The current data formatting and labeling standards for the Planetary Data System (PDS) are known as the PDS4 Standards. They supersede the PDS3 Standards, but they represent a complete redesign of the requirements and implementation, rather than even a major incremental revision, from the previous standard. At the heart of the PDS4 Standards lies a fundamental, philosophical change from the PDS3 paradigm: the PDS4 Standards clearly and specifically constrain the way that the bytes comprising observational data may be stored in their data files-that is, the data structures-to a much greater degree than the PDS3 Standards ever did, even in their most mature realization. In PDS4, the PDS has defined data structures optimized for the long-term preservation of observational data. We explore the history of the PDS and its standards through the examination of a single, simple data structure (the 2D image), to understand the evolutionary pressures on the data and on the PDS that led to the development of the archival data structure requirements for observational data at the core of the PDS4 standards.

Keywords: astroinformatics
Herschel Gould Belt Survey Observations of Dense Cores in the Cepheus Flare Clouds

We present Herschel SPIRE and PACS maps of the Cepheus Flare clouds L1157, L1172, L1228, L1241, and L1251, observed by the Herschel Gould Belt Survey of nearby star-forming molecular clouds. Through modified blackbody fits to the SPIRE and PACS data, we determine typical cloud column densities of (0.5-1.0) × 1021 cm-2 and typical cloud temperatures of 14-15 K. Using the getsources identification algorithm, we extract 832 dense cores from the SPIRE and PACS data at 160-500 μm. From placement in a mass versus size diagram, we consider 303 to be candidate prestellar cores, and 178 of these to be "robust" prestellar cores. From an independent extraction of sources at 70 μm, we consider 25 of the 832 dense cores to be protostellar. The distribution of background column densities coincident with candidate prestellar cores peaks at (2-4) × 1021 cm-2. About half of the candidate prestellar cores in Cepheus may have formed as a result of the widespread fragmentation expected to occur within filaments of "transcritical" line mass. The lognormal robust prestellar core mass function (CMF) drawn from all five Cepheus clouds peaks at 0.56 M⊙ and has a width of ∼0.5 dex, similar to that of Aquila's CMF. Indeed, the width of Cepheus's aggregate CMF is similar to the stellar system initial mass function (IMF). The similarity of CMF widths in different clouds and the system IMF suggests a common, possibly turbulent origin for seeding the fluctuations that evolve into prestellar cores and stars.

Keywords: interstellar medium; young stellar objects; star formation; protostars; initial mass function; dense interstellar clouds; molecular clouds; interstellar filaments
Spatially Resolved Chandra Spectroscopy of the Large Magellanic Cloud Supernova Remnant N132D

We perform detailed spectroscopy of the X-ray-brightest supernova remnant in the Large Magellanic Cloud (LMC), N132D, using Chandra archival observations. By analyzing the spectra of the entire well-defined rim, we determine the mean abundances for O, Ne, Mg, Si, S, and Fe for the local LMC environment. We find evidence of enhanced O on the northwestern and S on the northeastern blast wave. By analyzing spectra interior to the remnant, we confirm the presence of a Si-rich, relatively hot plasma (≳1.5 keV) that is also responsible for the Fe K emission. Chandra images show that the Fe K emission is distributed throughout the interior of the southern half of the remnant but does not extend out to the blast wave. We estimate the progenitor mass to be 15 ± 5 M⊙ using abundance ratios in different regions that collectively cover a large fraction of the remnant, as well as from the radius of the forward shock compared with models of an explosion in a cavity created by stellar winds. We fit ionizing and recombining plasma models to the Fe K emission and find that the current data cannot distinguish between the two, so the origin of the high-temperature plasma remains uncertain. Our analysis is consistent with N132D being the result of a core-collapse supernova in a cavity created by its intermediate-mass progenitor.

Keywords: core-collapse supernovae; interstellar medium; x-ray observatories; x-ray astronomy; plasma astrophysics; shocks; interstellar abundances; metallicity; large magellanic cloud; high resolution spectroscopy
Hidden Companions to Intermediate-mass Stars. XIX. Spin–Orbit Misalignment and a 0.26M ⊙, 1.8 au Companion in the Astrometric Binary Gamma Trianguli Australis

Gamma Trianguli Australis is a nearby A-type star that was reported to be a 488 days astrometric binary in Gaia DR3. Here we report on a VLTI/GRAVITY observation of γ TrA in which we did not detect the companion down to a K band flux ratio of 0.5%. From the isochrone mass M A = 3.04M ⊙ of the subgiant primary, this implies a semimajor axis a orb = 1.8 au and that the companion is a M B = 0.26M ⊙ M dwarf. The primary disk is partially resolved with an angular diameter θ 1 ≈ 1 mas ↔ 13.0R ⊙. The differential visibility phases across the Brγ absorption line allowed us to measure the longitude of the ascending node of the primary's rotational plane Ωrot = 212° ± 3°. This implies a spin–orbit misalignment of at least 27° ± 3° based on the Gaia astrometric solution. *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Keywords: astrometric binary stars; a stars; stellar rotation; optical interferometry
A Deep Study of an Intermediate-age Open Cluster SAI 35 (Juchert 20) Using Ground-based Imaging and Gaia EDR3 Astrometry

We present a CCD UBVI photometric study of poorly studied intermediate-age open cluster SAI 35 (Juchert 20) for the first time. To accomplish this study, we also used LAMOST DR5, Two Micron All Sky Survey, and Gaia EDR3 databases. We identified 214 most probable cluster members with membership probability higher than 50%. The mean proper motion of the cluster is found as ${\mu }_{\alpha }\cos \delta =1.10\pm 0.01$ <!-- --> and μδ = -1.66 ± 0.01 mas yr-1. We find the normal interstellar extinction law using the various two-color diagrams. The age, distance, reddening, and radial velocity of the cluster are estimated to be 360 ± 40 Myr, 2.9 ± 0.15 kpc, 0.72 ± 0.05 mag, and -91.62 ± 6.39 km s-1, respectively. The overall mass function slope for main-sequence stars is found to be 1.49 ± 0.16 within the mass range 1.1-3.1 M⊙, which is in agreement with Salpeter's value within uncertainty. The present study demonstrates that SAI 35 is dynamically relaxed. Galactic orbital parameters are determined using Galactic potential models. We found that this object follows a circular path around the Galactic center.

Keywords: open star clusters; astrometry; initial mass function; orbits; interstellar extinction
A New Transition Wolf-Rayet WN/C Star in the Milky Way

We report the discovery of a new transition type Wolf-Rayet (W-R) WN/C star in the Galaxy. According to its coordinates (R.A., decl.)J2000 = ${18}^{{\rm{h}}}{51}^{{\rm{m}}}39\buildrel{\rm{s}}\over{.} 7$ , -05°34'51"1, and the distance (7.11 ${}_{-1.22}^{+1.56}\,$ kpc away from Earth) inferred from the second Gaia data release, it is found that W-R 121-16 is located in the Far 3 kpc Arm, and it is 3.75 kpc away from the Galactic Center. The optical spectra obtained by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and the 2.16 m telescope, both located at the Xinglong Observatory in China, indicate that this is a W-R star of the transitional WN7o/WC subtype. A current stellar mass of about ${7.1}_{-1.1}^{+1.7}\,$ M⊙, a mass-loss rate of $\dot{M}={10}^{-{4.97}_{-0.20}^{+0.16}}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ , a bolometric luminosity of log L/L⊙ = ${4.88}_{-0.15}^{+0.17}$ , and a stellar temperature of ${T}_{* }={47}_{-5}^{+9}\,$ kK are derived by fitting the observed spectrum with a specific Potsdam W-R model. The magnitude in V-band varies between 13.95 and 14.14 mag, while no period is found. Based on the optical spectra, the time domain data, and the indices of the astrometric solution of the Gaia data, W-R 121-16 is likely a transitional WN/C single star rather than a WN+WC binary.

Keywords: wolf-rayet stars; massive stars; stellar distance; galaxy stellar content
The 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra

This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).

Keywords: astronomy databases; optical telescopes; infrared astronomy; redshift surveys; galactic abundances; stellar spectral lines; stellar properties