adsabs/SciX_UAT_keywords huggingface dataset:
The Ice Chemistry in Comets and Planet-forming Disks: Statistical Comparison of CH3OH, H2CO, and NH3 Abundance Ratios

Comets are frozen remnants of our solar system's formation, and comparing their chemical composition to that of planet-forming systems can reveal crucial insights about our origins, potentially answering one of the most challenging questions in planetary science, i.e., whether cometary material was mainly inherited from the protosolar nebula or reprocessed during the solar system formation. Here we provide the first statistical analysis of methanol, formaldehyde, and ammonia abundances in 35 comets and 11 protostellar solar analogs and planet-forming disks. We show that comets from different dynamical families have comparable compositions on average, implying that their chemistry is preserved even after formation. While abundances retrieved from infrared and (sub)millimeter ground-based observations are in agreement, there are significant differences with those obtained via mass spectroscopy for 67P/Churyumov–Gerasimenko, target of the ESA-Rosetta mission; we discuss the implication of relying solely on the latter data for comparisons with disk abundance ratios. Finally, we find a significant difference in the [CH3OH]/[H2CO] ratio in comets observed within or farther than 1 au from the Sun, suggesting that temperature-activated mechanisms can enhance the H2CO production in the coma; this bias can strongly influence our understanding of comet chemistry in the context of planet formation. When compared to planet-forming systems, the [CH3OH]/[H2CO] and [NH3]/[CH3OH] molecular abundance ratios in comets are consistent with those measured in Class 0 hot corinos and in the inner regions of Class II disks, hence suggesting an inheritance scenario.

Keywords: chemical abundances; abundance ratios; comets; comet origins; comet volatiles; planet formation; solar system formation
Exploring the Radio Spectral Energy Distribution of the Ultraluminous Radio-quiet Quasar SDSS J0100+2802 at Redshift 6.3

We report deep Karl G. Jansky Very Large Array (VLA) observations of the optically ultraluminous and radio-quiet quasar SDSS J010013.02+280225.8 (hereafter J0100+2802) at redshift z = 6.3. We detected the radio continuum emission at 1.5 GHz, 6 GHz, and 10 GHz. This leads to a radio power-law spectral index of α = -0.52 ± 0.18 (S ∝ ν α ). The radio source is unresolved in all VLA bands with an upper limit to the size of 0.″2 (i.e., ~1.1 kpc) at 10 GHz. We find variability in the flux density (increase by ~33%) and the spectral index (steepened) between observations in 2016 and 2017. We also find that the VLA 1.5 GHz flux density observed in the same year is 1.5 times that detected with the Very Long Baseline Array (VLBA) in 2016 at the same frequency. This difference suggests that half of the radio emission from J0100+2802 comes from a compact core within 40 pc, and the rest comes from the surrounding few-kiloparsec area, which is diffuse and resolved out in the VLBA observations. The diffuse emission is 4 times brighter than what would be expected if driven by star formation. We conclude that the central active galactic nucleus is the dominant power engine of the radio emission in J0100+2802.

Keywords: quasars; radio continuum emission; galaxies; high-redshift galaxies
Is the Far-ultraviolet Flux of 21 Com Anticorrelated to its Optical Brightness?

The comparison of 20 ultraviolet spectra of 21 Com taken over continuous 24 hr to the optical counts collected by the Fine Error Sensor on board IUE reveals that large variations observed shortwards of 1700 Å occur in anti-phase with the optical brightness for part of the observations but not all. In this data, the FUV flux at 1540 Å reaches a minimum at rotational phase 0.32 and increases afterwards while the FES counts continue to increase after this phase. The Fe II resonance line at 1608.45 Å is Doppler shifted by 0.13 Å at phase 0.00 and ‑0.13 Å at phase of FUV flux minimum.

Keywords: chemically peculiar stars
The Spatially Resolved Bipolar Nebula of Sakurai's Object. II. Mapping the Planetary Nebula Expansion

Observations of the ejecta from the final flash (FF) of helium shell burning in Sakurai's Object (V4334 Sgr) are presented for 2015-2019, a period ∼20-24 yr after discovery. Adaptive optics images at Ks trace the expanding debris. While most of the ejecta mass is in ∼200 K dust, a small fraction, ∼0.4%, of the dust mass is at ∼760 K. The 760 K continuum dominates the near-IR images. Spatial-spectral images in He I 10830 Å show an ∼1"6 diameter bipolar planetary nebula at position angle 21° ± 5° with the SW moving toward us and the NE moving away. Seen in integrated light, the nebula is nearly circular. Near-IR continuum images show ejecta moving radially away from a bright central point source. High-resolution mid-IR spectra reveal molecular hydrocarbon lines with an expansion velocity of 270 ± 5 km s-1 seen in absorption against the dust continuum. The hydrocarbons originate in material produced in the FF. The bipolar nebula and debris clouds are discussed in the context of a highly inclined disk model. The proper motion has been measured placing V4334 Sgr in the thick disk population. There is no evidence that a hot white dwarf Wolf-Rayet ([WR]) wind has emerged; no [WR] spectral features were detected. The possibility of a binary companion involved in the evolution is discussed.

Keywords: protoplanetary nebulae
A Physical Model for the UV/Optical Power Spectra of AGN

The UV/optical variability of active galactic nuclei (AGN) has long been thought to be driven by the X-ray illumination of the accretion disk. However, recent multiwavelength campaigns of nearby Seyfert galaxies seem to challenge this paradigm, with an apparent discrepancy between observations and the underlying theory. In order to further probe the connection between the UV/optical and X-ray variability in AGN, we developed a physical model to reproduce the UV/optical power spectral densities (PSDs) of AGN assuming the thermal reprocessing of the X-rays in the disk. This model offers a novel way to probe the innermost regions of AGN. We use our model to study the variability of NGC 5548, and we infer that the X-ray and UV/optical PSDs as well as the interband UV/optical time lags are all well reproduced. We also derive constraints on the source physical parameters, such as the X-ray corona height and the accretion rate. Our results suggest that X-ray disk reprocessing accounts for the full variability properties of this AGN, within the considered timescales. Using earlier data of NGC 5548, we also show that our model can reproduce its PSD in different epochs, establishing the feasibility of using PSD modeling to investigate the time evolution of a source.

Keywords: active galactic nuclei; x-ray active galactic nuclei; seyfert galaxies; accretion
Global Modeling of Nebulae with Particle Growth, Drift, and Evaporation Fronts. II. The Influence of Porosity on Solids Evolution

Incremental particle growth in turbulent protoplanetary nebulae is limited by a combination of barriers that can slow or stall growth. Moreover, particles that grow massive enough to decouple from the gas are subject to inward radial drift, which could lead to the depletion of most disk solids before planetesimals can form. Compact particle growth is probably not realistic. Rather, it is more likely that grains grow as fractal aggregates, which may overcome this so-called radial drift barrier because they remain more coupled to the gas than compact particles of equal mass. We model fractal aggregate growth and compaction in a viscously evolving solar-like nebula for a range of turbulent intensities α t = 10-5-10-2. We do find that radial drift is less influential for porous aggregates over much of their growth phase; however, outside the water snowline fractal aggregates can grow to much larger masses with larger Stokes numbers more quickly than compact particles, leading to rapid inward radial drift. As a result, disk solids outside the snowline out to ~10-20 au are depleted earlier than in compact growth models, but outside ~20 au material is retained much longer because aggregate Stokes numbers there remain lower initially. Nevertheless, we conclude even fractal models will lose most disk solids without the intervention of some leapfrog planetesimal forming mechanism such as the streaming instability (SI), though conditions for the SI are generally never satisfied, except for a brief period at the snowline for α t = 10-5.

Keywords: protoplanetary disks
Type IIP Supernova Progenitors. III. Blue to Red Supergiant Ratio in Low-metallicity Models with Convective Overshoot

The distribution of stars in the Hertzsprung-Russell diagram (HRD) for a stellar conglomeration represents a snapshot of its evolving stellar population. Some of the supergiant stars may transit the HRD from blue to red and then again to blue during their late evolutionary stages, as exemplified by the progenitor of SN 1987 A. Others may transit a given part of the HRD more than twice in a "blue loop" and end up as red supergiants before they explode. Since stars in blue loops spend a considerable part of their lives there, these stages may change the relative number of modeled supergiants in the HRD. Their lifetimes, in turn, depend upon the initial mass of the star, how convection in its interior is modeled, and how much mass loss takes place during its evolution. The observed ratio of the number of blue to red supergiants and yellow to red supergiants sensitively tests the stellar evolution theory. We compare modeled number ratios of these supergiants with observed data from the Large Magellanic Cloud, as it has a metallicity very similar to that of the environment of SN 2013ej. We successfully model these by taking into account moderate (exponential) convective overshooting. We explore its effect on the final radius and mass of the star prior to core collapse. The radius differs dramatically with overshoot. These factors controlling presupernova structure may affect the postexplosion optical/IR light curves and spectral development.

Keywords: massive stars; stellar evolutionary models; computational methods; blue loop; supergiant stars; type ii supernovae
Superflares, Chromospheric Activities, and Photometric Variabilities of Solar-type Stars from the Second-year Observation of TESS and Spectra of LAMOST

In this work, 1272 superflares on 311 stars are collected from 22,539 solar-type stars from the second-year observation of the Transiting Exoplanet Survey Satellite (TESS), which almost covered the northern hemisphere of the sky. Three superflare stars contain hot Jupiter candidates or ultrashort-period planet candidates. We obtain γ = -1.76 ± 0.11 of the correlation between flare frequency and flare energy ( ${dN}/{dE}\propto {E}^{-\gamma }$ <!-- --> ) for all superflares and get β = 0.42 ± 0.01 of the correlation between superflare duration and energy (Tduration ∝ Eβ), which supports that a similar mechanism is shared by stellar superflares and solar flares. Stellar photometric variability (Rvar) is estimated for all solar-type stars, and the relation of $E\propto {R}_{\mathrm{var}}^{3/2}$ <!-- --> is included. An indicator of chromospheric activity (S-index) is obtained by using data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) for 7454 solar-type stars. Distributions of these two properties indicate that the Sun is generally less active than superflare stars. We find that saturation-like feature of Rvar ∼ 0.1 may be the reason for superflare energy saturating around 1036 erg. Object TIC 93277807 was captured by the TESS first-year mission and generated the most energetic superflare. This superflare is valuable and unique in that it can be treated as an extreme event, which may be generated by different mechanisms than other superflares.

Keywords: stellar flares; g stars
The Early Solar System Abundance of Iron-60: New Constraints from Chondritic Silicates

The abundance of iron-60 in the early solar system is important for planetary evolution models, and has been hotly debated. To put further constraints on the initial 60Fe/56Fe ratio of the solar system, here we present new iron-nickel isotope data, measured in situ by NanoSIMS, for 14 silicate chondrules from three carbonaceous and three unequilibrated ordinary chondrites. NanoSIMS measurements were performed at high spatial resolution (200-300 nm primary beam diameter), to avoid inclusion of unwanted phases in the analysis volume. The average initial 60Fe/56Fe ratios that can be estimated from our pooled chondrule data are 2.1 (±1.3) × 10-7 and 0.8 (±1.0) × 10-7 for carbonaceous and ordinary chondrites, respectively (1σ uncertainties). The estimated average initial 60Fe/56Fe ratio of all analyzed chondrules is 1.0 (±0.7) × 10-7. These results are inconsistent with initial 60Fe/56Fe ratios >2.4 × 10-7 (2σ upper limit of our entire data set) reported in the literature for some chondrule silicates based on in situ isotope data, and agree better with our previously published in situ data on chondritic troilites (0.10 ± 0.15 × 10-7), as well as with 60Fe/56Fe ratios estimated from isotope data of bulk meteorites and chondrules (0.10-0.75 × 10-7). Our isotope data hint at a possible difference between the initial 60Fe/56Fe ratios of the early solar system's two major isotope reservoirs, with the carbonaceous chondritic reservoir having higher iron-60 abundance than the non-carbonaceous reservoir. Nevertheless, in light of similar hints in the literature, this possibility deserves further investigation.

Keywords: isotopic abundances; solar system
Formation of Mass Gap Objects in Highly Asymmetric Mergers

The LIGO/Virgo Collaboration (LVC) recently reported the detection of GW190814, a merger of a ${23}_{-0.9}^{+1.0}\,\,{M}_{\odot }$ primary black hole (BH), and a ${2.6}_{-0.08}^{+0.08}\,\,{M}_{\odot }$ secondary. The secondary's mass falls into the mass gap regime, which refers to the scarcity of compact objects in the mass range of 2-5 $\,{M}_{\odot }$ . The first clue to the formation of GW190814 lies in the fact that the primary is a very massive BH. We suggest that the secondary was born as a neutron star (NS) where a significant amount of the supernova ejecta mass from its formation remained bound to the binary due to the presence of the massive BH companion. The bound mass forms a circumbinary accretion disk, and its accretion onto the NS created a mass gap object. In this scenario, LIGO/Virgo will only detect mass gap objects in binary mergers with an extreme mass ratio. We also predict a correlation between the mass of the secondary and the mass of the primary in such asymmetric mergers. Our model can be tested with future data from the LVC's third observing run.

Keywords: ligo; astrophysical black holes; supernova remnants; neutron stars; compact objects; ejecta; supernovae
It Takes Two Planets in Resonance to Tango around K2-146

K2-146 is a cool, 0.358 ${M}_{\odot }$ dwarf that was found to host a mini-Neptune with a 2.67 day period. The planet exhibited strong transit timing variations (TTVs) of greater than 30 minutes, indicative of the presence of an additional object in the system. Here we report the discovery of the previously undetected outer planet in the system, K2-146 c, using additional photometric data. K2-146 c was found to have a grazing transit geometry and a 3.97 day period. The outer planet was only significantly detected in the latter K2 campaigns presumably because of precession of its orbital plane. The TTVs of K2-146 b and c were measured using observations spanning a baseline of almost 1200 days. We found strong anti-correlation in the TTVs, suggesting the two planets are gravitationally interacting. Our TTV and transit model analyses revealed that K2-146 b has a radius of 2.25 ± 0.10 ${R}_{\oplus }$ and a mass of 5.6 ± 0.7 ${M}_{\oplus }$ , whereas K2-146 c has a radius of ${2.59}_{-0.39}^{+1.81}$ ${R}_{\oplus }$ and a mass of 7.1 ± 0.9 ${M}_{\oplus }$ . The inner and outer planets likely have moderate eccentricities of e = 0.14 ± 0.07 and 0.16 ± 0.07, respectively. Long-term numerical integrations of the two-planet orbital solution show that it can be dynamically stable for at least 2 Myr. We show that the resonance angles of the planet pair are librating, which may be an indication that K2-146 b and c are in a 3:2 mean motion resonance. The orbital architecture of the system points to a possible convergent migration origin.

Keywords: exoplanet astronomy; transit photometry; timing variation methods; mini neptunes; exoplanet systems; photometry; astrometric exoplanet detection; transit timing variation method
Comprehensive Study of Mass Ejection and Nucleosynthesis in Binary Neutron Star Mergers Leaving Short-lived Massive Neutron Stars

By performing general relativistic hydrodynamics simulations with an approximate neutrino radiation transfer, the properties of ejecta in the dynamical and post-merger phases are investigated in the cases in which the remnant massive neutron star collapses into a black hole in ≲20 ms after the onset of the merger. The dynamical mass ejection is investigated in three-dimensional simulations. The post-merger mass ejection is investigated in two-dimensional axisymmetric simulations with viscosity using the three-dimensional post-merger systems as the initial conditions. We show that the typical neutron richness of the dynamical ejecta is higher for the merger of more asymmetric binaries; hence, heavier r-process nuclei are dominantly synthesized. The post-merger ejecta are shown to have only mild neutron richness, which results in the production of lighter r-process nuclei, irrespective of the binary mass ratios. Because of the larger disk mass, the post-merger ejecta mass is larger for more asymmetric binary mergers. Thus, the post-merger ejecta can compensate for the underproduced lighter r-process nuclei for asymmetric merger cases. As a result, by summing up both ejecta components, the solar residual r-process pattern is reproduced within the average deviation of a factor of three, irrespective of the binary mass ratio. Our result also indicates that the (about a factor of a few) light-to-heavy abundance scatter observed in r-process-enhanced stars can be attributed to variation in the binary mass ratio and total mass. Implications of our results associated with the mass distribution of compact neutron star binaries and the magnetar scenario of short gamma-ray bursts are discussed.

Keywords: r-process; neutron stars
GaMPEN: A Machine-learning Framework for Estimating Bayesian Posteriors of Galaxy Morphological Parameters

We introduce a novel machine-learning framework for estimating the Bayesian posteriors of morphological parameters for arbitrarily large numbers of galaxies. The Galaxy Morphology Posterior Estimation Network (GaMPEN) estimates values and uncertainties for a galaxy's bulge-to-total-light ratio (L B /L T ), effective radius (R e ), and flux (F). To estimate posteriors, GaMPEN uses the Monte Carlo Dropout technique and incorporates the full covariance matrix between the output parameters in its loss function. GaMPEN also uses a spatial transformer network (STN) to automatically crop input galaxy frames to an optimal size before determining their morphology. This will allow it to be applied to new data without prior knowledge of galaxy size. Training and testing GaMPEN on galaxies simulated to match z < 0.25 galaxies in Hyper Suprime-Cam Wide g-band images, we demonstrate that GaMPEN achieves typical errors of 0.1 in L B /L T , 0.″17 (~7%) in R e , and 6.3 × 104 nJy (~1%) in F. GaMPEN's predicted uncertainties are well calibrated and accurate (<5% deviation)-for regions of the parameter space with high residuals, GaMPEN correctly predicts correspondingly large uncertainties. We also demonstrate that we can apply categorical labels (i.e., classifications such as highly bulge dominated) to predictions in regions with high residuals and verify that those labels are ≳97% accurate. To the best of our knowledge, GaMPEN is the first machine-learning framework for determining joint posterior distributions of multiple morphological parameters and is also the first application of an STN to optical imaging in astronomy.

Keywords: galaxies; galaxy classification systems; astronomy data analysis; convolutional neural networks; neural networks; galactic and extragalactic astronomy
Orbit of the Patroclus–Menoetius Binary System and Predictions for the 2024/2025 Mutual Events Season

We report on the ephemeris development for Menoetius, the satellite of Patroclus. Our data set consisted of ground–based and Hubble Space Telescope relative astrometry, as well as 42 lightcurves from the mutual events seasons in 2007, 2012, and 2017/2018. Our dynamical model included the effects of oblate, nonspherical shapes of the components, and we assumed that Menoetius contained ∼22% of the system's mass. We numerically integrated the equations of motion and obtained a set of dynamical parameters that fit the data. We report the fit results in terms of residuals, state vectors, orbital elements and their 1σ uncertainties. The mean osculating semimajor axis is a = 692.5 ± 4.0 km, the mean eccentricity is e = 0.004 ± 0.004, and the International Celestial Reference Frame pole direction in R.A. and decl. is R. A. = 178.0 ± 0.5 deg, δ = ‑74.1 ± 0.2 deg. We determined the siderial orbital period of P = 4.282753 ± 0.000023 days. The fit yielded the system GM = 0.0950 ± 0.0012 km3 s‑2, which, in combination with the system volume determined from the stellar occultation and the assumed volume uncertainty of 20%, suggests a system bulk density of 1.05 ± 0.21 g cm‑3(1σ). The next season of mutual events starts in February of 2024 and lasts until January of 2025. The Patroclus system is in opposition for the observers on Earth in late September and is suitable for observations of the mutual events with an edge-on geometry in October.

Keywords: jupiter trojans; orbital elements; asteroid satellites
Utilizing a Global Network of Telescopes to Update the Ephemeris for the Highly Eccentric Planet HD 80606 b and to Ensure the Efficient Scheduling of JWST

The transiting planet HD 80606 b undergoes a 1000 fold increase in insolation during its 111 days orbit due to it being highly eccentric (e = 0.93). The planet's effective temperature increases from 400 to over 1400 K in a few hours as it makes a rapid passage to within 0.03 au of its host star during periapsis. Spectroscopic observations during the eclipse (which is conveniently oriented a few hours before periapsis) of HD 80606 b with the James Webb Space Telescope (JWST) are poised to exploit this highly variable environment to study a wide variety of atmospheric properties, including composition, chemical and dynamical timescales, and large scale atmospheric motions. Critical to planning and interpreting these observations is an accurate knowledge of the planet's orbit. We report on observations of two full-transit events: 2020 February 7 as observed by the TESS spacecraft and 2021 December 7-8 as observed with a worldwide network of small telescopes. We also report new radial velocity observations which, when analyzed with a coupled model to the transits, greatly improves the planet's orbital ephemeris. Our new orbit solution reduces the uncertainty in the transit and eclipse timing of the JWST era from tens of minutes to a few minutes. When combined with the planned JWST observations, this new precision may be adequate to look for non-Keplerian effects in the orbit of HD 80606 b.

Keywords: exoplanets; observational astronomy; orbit determination