adsabs/SciX_UAT_keywords huggingface dataset:
Uranus in Northern Midspring: Persistent Atmospheric Temperatures and Circulations Inferred from Thermal Imaging

We present results from mid-infrared imaging of Uranus at wavelengths of 13.0 and 18.7 μm, sensing emission from the stratosphere and upper troposphere, acquired using the VISIR instrument at the Very Large Telescope, 2018 September 4-October 20. Using a combination of inverse and forward modeling, we analyze these northern midspring (L s ∼ 46°) images and compare them to archival data to assess seasonal changes since the 1986 southern solstice and subsequent equinox. We find the data are consistent with little change (<0.3 K) in the upper tropospheric temperature structure, extending the previous conclusions of Orton et al. well past equinox, with only a subtle increase in temperature at the emerging north pole. Additionally, spatial-temporal variations in 13 μm stratospheric emission are investigated for the first time, revealing meridional variation and a hemispheric asymmetry not predicted by models. Finally, we investigate the nature of the stratospheric emission and demonstrate that the observed distribution appears related and potentially coupled to the underlying tropospheric emission six scale heights below. The observations are consistent with either midlatitude heating or an enhanced abundance of acetylene. Considering potential mechanisms and additional observations, we favor a model of acetylene enrichment at midlatitudes resulting from an extension of the upper tropospheric circulation, which appears capable of transporting methane from the troposphere, through the cold trap, and into the stratosphere for subsequent photolysis to acetylene.

Keywords: atmospheric circulation; uranus; atmospheric science; planetary atmospheres; planetary science; solar system gas giant planets
A Method to Extract Spatially Resolved Polycyclic Aromatic Hydrocarbon Emission from Spitzer Spectra: Application to M51

The mid-infrared spectrum contains rich diagnostics to probe the physical properties of galaxies, among which the pervasive emission features from polycyclic aromatic hydrocarbons (PAHs) offer promising means of estimating the star formation rate (SFR) relatively immune from dust extinction. This paper investigates the effectiveness of PAH emission as a SFR indicator on subkiloparsec scales by studying the Spitzer/IRS mapping-mode observations of the nearby grand-design spiral galaxy M51. We present a new approach of analyzing the spatial elements of the spectral data cube that simultaneously maximizes spatial resolution and spatial coverage, while yielding reliable measurements of the total, integrated 5-20 μm PAH emission. We devise a strategy of extracting robust PAH emission using spectra with only partial spectral coverage, complementing missing spectral regions with properly combined mid-infrared photometry. We find that in M51 the PAH emission correlates tightly with the extinction-corrected far-ultraviolet, near-ultraviolet, and Hα emission, from scales of ∼0.4 kpc close to the nucleus to 6 kpc out in the disk of the galaxy, indicating that PAH serves as an excellent tracer of SFR over a wide range of galactic environments. But regional differences exist. Close to the active nucleus of M51 the 6.2 μm feature is weaker, and the overall level of PAH emission is suppressed. The spiral arms and the central star-forming region of the galaxy emit stronger 7.7 and 8.6 μm PAH features than the inter-arm regions.

Keywords: interstellar medium; interstellar molecules; interstellar extinction; interstellar emissions; star formation; active galactic nuclei
Possible Supercritical Accretion on the Ultraluminous X-Ray Source in the Metal-poor Galaxy I Zw 18

We present an analysis of X-ray observations of the ultraluminous X-ray source (ULX) in I Zw 18 based on archival data taken with Chandra, XMM-Newton, and Suzaku. This ULX is considered to be an intermediate-mass black hole candidate simply because it is in the lowest-metallicity environment among ULXs, where the formation of heavy black holes is facilitated. However, actual study of the ULX based on observations spanning for a long period has been too limited to determine its nature. In this study, we investigate the spectral evolution of the ULX up to 2014, combining the previously unpublished Suzaku data with those from the other two satellites. We derive a positive correlation of between the bolometric luminosity L and inner-disk temperature T in on the basis of the multicolor disk blackbody model, where we exclude the Chandra data, which have the lowest luminosity and systematic residuals in the fitting. The nominal relation for the standard disk is rejected at a significance level of 1.5%. These results suggest that the ULX was in the slim-disk state during these observations except at the time of the Chandra observation, in which the ULX was likely to be in a different state. The apparent inner-disk radius appears negatively correlated with the inner-disk temperature. Moreover, we find a radial dependence of the disk temperature of T(r) ∝ r ‑p with p < 0.75, which also supports the hypothesis that the ULX has a slim disk. Therefore, the I Zw 18 ULX is most likely to be powered by a stellar-mass compact object in supercritical accretion.

Keywords: ultraluminous x-ray sources; x-ray transient sources; high mass x-ray binary stars; blue compact dwarf galaxies
Chandra Resolves the Double FU Orionis System RNO 1B/1C in X-Rays

We present new Chandra X-ray observations of the close pair of young stars RNO 1B and 1C (6″ separation) located in the L1287 cloud. RNO 1B erupted in 1978-1990 and is classified as an FU Orionis star (FUor). RNO 1C also shows most of the properties of an FUor but no eruption has been seen yet. Only a few dozen FUors are known and the presence of two such objects with a small angular separation is rare, suggesting a common origin. Both stars were faintly detected by Chandra and we summarize their X-ray properties within the framework of other previously detected FUors. We also report other X-ray detections in L1287 including the deeply embedded young star RNO 1G, the jet-like radio source VLA 3, and an enigmatic hard flaring source with no Two Micron All Sky Survey counterpart that was only detected in the second of the two Chandra exposures.

Keywords: young stellar objects; fu orionis stars; t tauri stars
A Pluto-Charon Concerto: An Impact on Charon as the Origin of the Small Satellites

We consider a scenario where the small satellites of Pluto and Charon grew within a disk of debris from an impact between Charon and a trans-Neptunian object (TNO). After Charon's orbital motion boosts the debris into a disk-like structure, rapid orbital damping of meter-sized or smaller objects is essential to prevent the subsequent reaccretion or dynamical ejection by the binary. From analytical estimates and simulations of disk evolution, we estimate an impactor radius of 30-100 km; smaller (larger) radii apply to an oblique (direct) impact. Although collisions between large TNOs and Charon are unlikely today, they were relatively common within the first 0.1-1 Gyr of the solar system. Compared to models where the small satellites agglomerate in the debris left over by the giant impact that produced the Pluto-Charon binary planet, satellite formation from a later impact on Charon avoids the destabilizing resonances that sweep past the satellites during the early orbital expansion of the binary.

Keywords: pluto; natural satellites (solar system); planet formation; kuiper belt; trans-neptunian objects
The Gateway from Centaurs to Jupiter-family Comets: Thermal and Dynamical Evolution

It was recently proposed that there exists a "gateway" in the orbital parameter space through which Centaurs transition to Jupiter-family comets (JFCs). Further studies have implied that the majority of objects that eventually evolve into JFCs should leave the Centaur population through this gateway. This may be naively interpreted as gateway Centaurs being pristine progenitors of JFCs. This is the point we want to address in this work. We show that the opposite is true: gateway Centaurs are, on average, more thermally processed than the rest of the population of Centaurs crossing Jupiter's orbit. Using a dynamically validated JFC population, we find that only ~20% of Centaurs pass through the gateway prior to becoming JFCs, in accordance with previous studies. We show that more than half of JFC dynamical clones entering the gateway for the first time have already been JFCs-they simply avoided the gateway on their first pass into the inner solar system. By coupling a thermal evolution model to the orbital evolution of JFC dynamical clones, we find a higher than 50% chance that the layer currently contributing to the observed activity of gateway objects has been physically and chemically altered, due to previously sustained thermal processing. We further illustrate this effect by examining dynamical clones that match the present-day orbits of 29P/Schwassmann-Wachmann 1, P/2019 LD2 (ATLAS), and P/2008 CL94 (Lemmon).

Keywords: comets; comet volatiles; comet nuclei; short period comets; comet dynamics; computational methods
SOFIA+FORCAST Lunar Legacy Project Processing Procedure

The aim of the Lunar Legacy Project is to map the distribution of water on the Moon's surface through the detection and characterization of the 6 μm spectral band indicative of molecular water. Spectra were taken with the Faint Object infraRed Camera for the SOFIA Telescope instrument on the Stratospheric Observatory for Infrared Astronomy (SOFIA) between 2018 and 2022. This paper describes the processing steps necessary to reduce the raw data downloaded from the SOFIA archive to create flux-calibrated spectra. The reduction mostly requires the SOFIA Redux package which can be downloaded from the SOFIA website, and some steps in the process require scripts written by our team in Python.

Keywords: spectroscopy; infrared telescopes; the moon; lunar surface
Statistical Study on Spatial Distribution and Polarization of Saturn Narrowband Emissions

The spatial distribution and polarization of Saturn narrowband (NB) emissions have been studied by using Cassini Radio and Plasma Wave Sciences data and goniopolarimetric data obtained through an inversion algorithm with a preset source located at the center of Saturn. From 2004 January 1 to 2017 September 12, NB emissions were selected automatically by a computer program and rechecked manually. The spatial distribution shows a preference for high latitude and intensity peaks in the region within 6 Saturn radii (Rs) for both 5 and 20 kHz NB emissions. 5 kHz NB emissions also show a local time preference roughly in the 18:00-22:00 sector. The Enceladus plasma torus makes it difficult for NB emissions to propagate to the low latitude regions outside the plasma torus. The extent of the low latitude regions where 5 and 20 kHz NB emissions were never observed is consistent with the corresponding plasma torus density contour in the meridional plane. 20 kHz NB emissions show a high circular polarization while 5 kHz NB emissions are less circularly polarized with $\left|V\right|\lt 0.6$ for majority of the cases. And cases of 5 kHz NB emissions with high circular polarization are more frequently observed at high latitude especially at the northern and southern edges of the Enceladus plasma torus.

Keywords: magnetospheric radio emissions; saturn; planetary magnetospheres
A MIRI Search for Planets and Dust around WD 2149+021

The launch of JWST has ushered in a new era of high-precision infrared astronomy, allowing us to probe nearby white dwarfs for cold dust, exoplanets, and tidally heated exomoons. While previous searches for these exoplanets have successfully ruled out companions as small as 7–10 Jupiter masses (M Jup), no instrument prior to JWST has been sensitive to the likely more common sub-Jovian-mass planets around white dwarfs. In this paper, we present the first multiband photometry (F560W, F770W, F1500W, F2100W) taken of WD 2149+021 with the Mid-Infrared Instrument on JWST. After a careful search for both resolved and unresolved planets, we do not identify any compelling candidates around WD 2149+021. Our analysis indicates that we are sensitive to companions as small as ∼0.5 M Jup outwards of 1.″263 (28.3 au) and ∼1.0 M Jup at the innermost working angle (0.″654, 14.7 au) at 3 Gyr with 5σ confidence, placing significant constraints on any undetected companions around this white dwarf. The results of these observations emphasize the exciting future of sub-Jovian planet detection limits by JWST, which can begin to constrain how often these planets survive their host stars' evolution.

Keywords: exoplanet astronomy; circumstellar dust; white dwarf stars; high contrast techniques; direct imaging; photometry
Validation of the Gaia Early Data Release 3 Parallax Zero-point Model with Asteroseismology

Gaia Early Data Release 3 (EDR3) provides trigonometric parallaxes for 1.5 billion stars, with reduced systematics compared to Gaia Data Release 2 and reported precisions better by up to a factor of 2. New to EDR3 is a tentative model for correcting the parallaxes of magnitude-, position-, and color-dependent systematics for five- and six-parameter astrometric solutions, Z5 and Z6. Using a sample of over 2000 first-ascent red giant branch stars with asteroseismic parallaxes, I perform an independent check of the Z5 model in a Gaia magnitude range of 9 ≲ G ≲ 13 and color range of 1.4 μm-1 ≲ νeff ≲ 1.5 μm-1. This analysis therefore bridges the Gaia team's consistency check of Z5 for G > 13 and indications from independent analysis using Cepheids of a ≈15 μas overcorrection for G < 11. I find overcorrection sets in at G ≲ 10.8, such that Z5-corrected EDR3 parallaxes are larger than asteroseismic parallaxes by 15 ± 3 μas. For G ≳ 10.8, EDR3 and asteroseismic parallaxes in the Kepler field agree up to a constant consistent with expected spatial variations in EDR3 parallaxes after a linear, color-dependent adjustment. I also infer an average underestimation of EDR3 parallax uncertainties in the sample of 22% ± 6%, consistent with the Gaia team's estimates at similar magnitudes and independent analysis using wide binaries. Finally, I extend the Gaia team's parallax spatial covariance model to brighter magnitudes (G < 13) and smaller scales (down to ≈0°1), where systematic EDR3 parallax uncertainties are at least ≈3-4 μas.

Keywords: parallax; asteroseismology; red giant stars; stellar distance
Distribution of s-, r-, and p-process Nuclides in the Early Solar System Inferred from Sr Isotope Anomalies in Meteorites

Nucleosynthetic isotope anomalies in meteorites allow distinguishing between the noncarbonaceous (NC) and carbonaceous (CC) meteorite reservoirs and show that correlated isotope anomalies exist in both reservoirs. It is debated, however, whether these anomalies reflect thermal processing of presolar dust in the disk or are primordial heterogeneities inherited from the solar system's parental molecular cloud. Here, using new high-precision 84Sr isotope data, we show that NC meteorites, Mars, and the Earth and Moon are characterized by the same 84Sr isotopic composition. This 84Sr homogeneity of the inner solar system contrasts with the well-resolved and correlated isotope anomalies among NC meteorites observed for other elements, and most likely reflects correlated s- and (r, p)-process heterogeneities leading to 84Sr excesses and deficits of similar magnitude, which cancel each other out. For the same reason there is no clearly resolved 84Sr difference between NC and CC meteorites, because in some carbonaceous chondrites the characteristic 84Sr excess of the CC reservoir is counterbalanced by an 84Sr deficit resulting from s-process variations. Nevertheless, most carbonaceous chondrites exhibit 84Sr excesses, which reflect admixture of refractory inclusions and more pronounced s-process heterogeneities in these samples. Together, the correlated variation of s- and (r, p)-process nuclides revealed by the 84Sr data of this study refute an origin of these isotope anomalies solely by processing of presolar dust grains, but points to primordial mixing of isotopically distinct dust reservoirs as the dominant process producing the isotopic heterogeneity of the solar system.

Keywords: cosmochemistry; small solar system bodies; meteorites; protoplanetary disks; planetary system formation
Photometric and Spectroscopic Studies of the Long-Period Low-Mass-Ratio Deep-Contact Binary KN Per

Photometric analysis and spectroscopic study of the long-period low-mass-ratio deep-contact binary KN Per were performed. The light curves of the BV(RI) c band were from the Ningbo Bureau of Education and Xinjiang Observatory Telescope at the Xingming Observatory. Through the analysis of the Wilson-Devinney program, KN Per was found as an A-type low-mass-ratio deep-contact binary (q = 0.236; f = 53.4%). A cool spot applied on the primary component was introduced to explain the unequal maxima of the light curve. Based on the O - C analysis, we found that the rate of the increasing orbital period is $\dot{P}$ = 5.12 ± (0.30) × 10-7 day yr-1, meaning the mass transfer from the secondary component to the primary one. By analyzing the spectroscopic data, we detected chromospheric activity emission line indicators, which correspond to the light-curve analysis. Seventy-one long-period (P > 0.5 day) contact binaries, including our target, were collected. The evolutionary states of all collected stars were investigated by the illustrations of mass-radius, mass-luminosity, and log M T -log J o . The relations of some physical parameters were also determined. With the instability parameters of KN Per, we determined that it is a stable contact binary system at present.

Keywords: binary stars; contact binary stars; eclipsing binary stars; magnetic stars
Spectral Evolution of Ultraluminous X-Ray Pulsar NGC 300 ULX-1

We report on results from a 1 yr soft X-ray observing campaign of the ultraluminous X-ray pulsar NGC 300 ULX-1 by the Neutron star Interior Composition Explorer (NICER) during 2018-2019. Our analysis also made use of data from Swift/XRT and XMM-Newton in order to model and remove contamination from the nearby eclipsing X-ray binary NGC 300 X-1. We constructed and fitted a series of 5 day averaged NICER spectra of NGC 300 ULX-1 in the 0.4-4.0 keV range to evaluate the long-term spectral evolution of the source, and we found that an absorbed power-law model provided the best fit overall. Over the course of our observations, the source flux (0.4-4.0 keV; absorbed) dimmed from 2 × 10-12 to below 10-13 erg s-1 cm-2 and the spectrum softened, with the photon index going from Γ ≈ 1.6 to Γ ≈ 2.6. We interpret the spectral softening as reprocessed emission from the accretion disk edge coming into view while the pulsar was obscured by the possibly precessing disk. Some spectral fits were significantly improved by the inclusion of a disk blackbody component, and we surmise that this could be due to the pulsar emerging in between obscuration episodes by partial covering absorbers. We posit that we observed a low-flux state of the system (due to line-of-sight absorption) punctuated by the occasional appearance of the pulsar, indicating short-term source variability nested in longer-term accretion disk precession timescales.

Keywords: pulsars; ultraluminous x-ray sources; high mass x-ray binary stars
The Radio Parallax of the Crab Pulsar: A First VLBI Measurement Calibrated with Giant Pulses

We use four observations with the European very long baseline interferometry (VLBI) network to measure the first precise radio parallax of the Crab Pulsar. We found two in-beam extragalactic sources just outside the Crab Nebula, with one bright enough to use as a background reference source in our data. We use the Crab Pulsar's giant pulses to determine fringe and bandpass calibration solutions, which greatly improved the sensitivity and reliability of our images and allowed us to determine precise positional offsets between the pulsar and the background source. From those offsets, we determine a parallax of π = 0.53 ± 0.06 mas and proper motion of (μ α , μ δ ) = (-11.34 ± 0.06, 2.65 ± 0.14) mas yr-1, yielding a distance of $d={1.90}_{-0.18}^{+0.22}\,\mathrm{kpc}$ and transverse velocity of ${v}_{\perp }={104}_{-11}^{+13}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . These results are consistent with the Gaia 3 measurements, and open up the possibility of far more accurate astrometry with further VLBI observations.

Keywords: very long baseline interferometry; supernova remnants; radio bursts; radio astrometry; pulsars; parallax
Ring Seismology of the Ice Giants Uranus and Neptune

We assess the prospect of using ring seismology to probe the interiors of the ice giants Uranus and Neptune. We do this by calculating normal-mode spectra for different interior models of Uranus and Neptune using the stellar oscillation code GYRE. These spectra provide predictions of where in these planets' ring systems the effects of interior oscillations might be detected. We find that f-mode resonances with azimuthal order m = 2 or 7 ≤ m ≤ 19 fall among the inner rings (6, 5, 4, α, and β) of Uranus, while f-mode resonances with 2 ≤ m ≤ 12 fall in the tenuous ζ ring region. In addition, f-mode resonances with m = 2 or 6 ≤ m ≤ 13 may give azimuthal structure to Neptune's tenuous Galle ring. We also find that g-mode resonances may fall in the middle to outer rings of these planets. Although an orbiter is most likely required to confirm the association between any waves in the rings and planetary normal modes, the diversity of normal-mode spectra implies that identification of just one or two modes in the rings of Uranus or Neptune would eliminate a variety of interior models and thus aid in the interpretation of Voyager observations and future spacecraft measurements.

Keywords: planetary rings; orbits; orbital resonances; uranus; neptune; solar system gas giant planets; planetary dynamics
The Orbit and Density of the Jupiter Trojan Satellite System Eurybates-Queta

We report observations of the Jupiter Trojan asteroid (3548) Eurybates and its satellite Queta with the Hubble Space Telescope and use these observations to perform an orbital fit to the system. Queta orbits Eurybates with a semimajor axis of 2350 ± 11 km at a period of 82.46 ± 0.06 days and an eccentricity of 0.125 ± 0.009. From this orbit we derive a mass of Eurybates of 1.51 ± 0.03 × 1017 kg, corresponding to an estimated density of 1.1 ± 0.3 g cm-3, broadly consistent with densities measured for other Trojans, C-type asteroids in the outer main asteroid belt, and small icy objects from the Kuiper Belt. Eurybates is the parent body of the only major collisional family among the Jupiter Trojans; its low density suggests that it is a typical member of the Trojan population. Detailed study of this system in 2027 with the Lucy spacecraft flyby should allow significant insight into collisional processes among what appear to be the icy bodies of the Trojan belt.

Keywords: asteroid satellites; jupiter trojans