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41. Comet C/2017 E4 composition with iSHELL at NASA/IRTF
ID:
ivo://CDS.VizieR/J/AJ/156/68
Title:
Comet C/2017 E4 composition with iSHELL at NASA/IRTF
Short Name:
J/AJ/156/68
Date:
21 Oct 2021
Publisher:
CDS
Description:
In 2017 April, we acquired comprehensive high-resolution spectra of newly discovered comet C/2017 E4 (Lovejoy) as it approached perihelion, and before its disintegration. We detected many cometary emission lines in the range (2.8-5.3) {mu}m, in four customized instrument settings (L1-c, L3, Lp1-c, and M1) of iSHELL - the new near-IR high-resolution immersion echelle spectrograph at NASA/IRTF (Maunakea, Hawaii). We identified 12 molecular species: nine primary volatiles (H_2_O, HCN, NH_3_, CO, C_2_H_2_, C_2_H_6_, CH_4_, CH_3_OH, H_2_CO) and three product species (CN, NH_2_, OH). We detected 85 H_2_O emission lines from 12 water vibrational bands across L1-c and M1 settings. The many detected water emission lines enabled retrieval of accurate measures for ortho- and para-H_2_O independently, thereby reducing systematic uncertainty in the derived ortho-para ratio and nuclear spin temperature. Excitation analyses and emission profile analyses were performed for all species, and molecular abundance ratios relative to water are compared with values found for other Oort Cloud comets in our infrared database. Abundance ratios are consistent for most species, with the exception of underabundant methanol and overabundant ammonia in E4.
42. Comet C/2020 F3 (NEOWISE) emission lines
ID:
ivo://CDS.VizieR/J/A+A/656/A160
Title:
Comet C/2020 F3 (NEOWISE) emission lines
Short Name:
J/A+A/656/A160
Date:
21 Mar 2022 09:16:33
Publisher:
CDS
Description:
Comet C/2020 F3 (NEOWISE) is considered to be the brightest comet observed in the northern hemisphere since the passage of comet C/1995 O1 (Hale-Bopp) in 1997. Since the study of comets offers a unique opportunity to investigate the early stages of the formation and evolution of our Sun and the Solar System, we obtained high-resolution optical spectra (R={lambda}/{Delta}{lambda}=115000) of comet NEOWISE. The unique passage and its brightness yielded spectra with a large number of emission lines, providing information on the coma composition and the physical and chemical processes occurring in the nucleus. The spectra have been used to generate a catalog of emission lines to be used for future studies of comets since there are no catalogs in the literature with such a high spectral resolution. Two high-resolution spectra of comet NEOWISE were obtained, on 26 July 2020 (geocentric distance of 0.7au) and 5 August 2020 (geocentric distance of 0.89au), with the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) echelle spectrograph installed on the 360cm Telescopio Nazionale Galileo (TNG). The spectra cover the range between 383 and 693nm, and have been extracted using the HARPS-N Data Reduction Pipeline. To analyze the spectra and compile the high-resolution catalog, we collected several laboratory molecular line lists that cover the same wavelength range as that of our spectra. To validate the final identification, we compared our catalog with other atlases that resulted from the spectral analysis of other comets. We generate a high-spectral-resolution catalog of emission lines observed in comet NEOWISE, providing the identification for 4488 lines. We found cometary lines due to CN, CH, C_2_, C_3_, and NH_2_ and atomic lines due to NaI and [OI].
43. Comet 67P/Churyumov-Gerasimenko FUV aurora
ID:
ivo://CDS.VizieR/J/A+A/647/A119
Title:
Comet 67P/Churyumov-Gerasimenko FUV aurora
Short Name:
J/A+A/647/A119
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to determine whether dissociative excitation of cometary neutralsby electron impact is the major source of far-ultraviolet (FUV) emissions at comet 67P/Churyumov-Gerasimenkoin the southern hemisphere at large heliocentric distances, both during quiet conditions and impacts of corotating interaction regions observed in the summer of 2016. We combined multiple datasets from the Rosetta mission through a multi-instrument analysis to complete the first forward modelling of FUV emissions in the southern hemisphere of comet 67P and compared modelled brightnesses to observations with the Alice FUV imaging spectrograph. We modelled the brightness of OI1356, OI1304, Lyman-beta, CI1657, and CII1335 emissions, which are associated with the dissociation products of the four major neutral species in the coma: CO2, H2O, CO, and O2. The suprathermal electron population was probed by the Ion and Electron Sensor of theRosetta Plasma Consortium (RPC/IES) and the neutral column density was constrained by several instruments: the RosettaOrbiter Spectrometer for Ion and Neutral Analysis (ROSINA), the Microwave Instrument for the Rosetta Orbiter (MIRO)and the Visual InfraRed Thermal Imaging Spectrometer (VIRTIS). The modelled and observed brightnesses of the FUV emission lines agree closely when viewing nadir and dissociative excitation by electron impact is shown to be the dominant source of emissions away from perihelion. The CII1335 emissions are shown to be consistent with the volume mixing ratio of CO derived from ROSINA. When viewing the limb during the impacts of corotating interaction regions, the model reproduces brightnesses of OI1356 and CI1657 well, but resonance scattering in the extended coma may contribute significantly to the observed Lyman-beta and OI1304 emissions. The correlation between variations in the suprathermal electron flux and the observed FUV line brightnesses when viewing the comet's limb suggests electrons are accelerated on large scales and that they originate in the solar wind. This means that the FUV emissions are auroral in nature.
44. Comet 46P/Wirtanen millimetre-wave spectra
ID:
ivo://CDS.VizieR/J/A+A/648/A49
Title:
Comet 46P/Wirtanen millimetre-wave spectra
Short Name:
J/A+A/648/A49
Date:
08 Feb 2022
Publisher:
CDS
Description:
We present the results of a molecular survey of comet 46P/Wirtanen undertaken with the IRAM 30-m and NOEMA radio telescopes in December 2018. Observations at IRAM 30-m during the 12-18 Dec. period comprise a 2mm spectral survey, which covers 25GHz, and a 1mm survey which covers 62GHz. The gas outflow velocity and kinetic temperature have been accurately constrained by the observations. We derive abundances of 11 molecules, some being identified remotely for the first time in a Jupiter-family comet, including complex organic molecules such as formamide, ethylene glycol, acetaldehyde or ethanol. Sensitive upper limits on the abundances of 24 other molecules are obtained. The comet is found to be relatively rich in methanol (3.4% relative to water) but relatively depleted in CO, CS, HNC, HNCO or HCOOH.
45. Convective blueshifts in solar atmos.
ID:
ivo://CDS.VizieR/J/A+A/624/A57
Title:
Convective blueshifts in solar atmos.
Short Name:
J/A+A/624/A57
Date:
21 Oct 2021
Publisher:
CDS
Description:
Convective motions in the solar atmosphere cause spectral lines to become asymmetric and shifted in wavelength. For photospheric lines, this differential Doppler shift varies from the solar disk center to the limb. Precise and comprehensive observations of the convective blueshift and its center-to-limb variation improve our understanding of the atmospheric hydrodynamics and ensuing line formation, and provide the basis to refine 3D models of the solar atmosphere. We performed systematical spectroscopic measurements of the convective blueshift of the quiet Sun with the Laser Absolute Reference Spectrograph (LARS) at the German Vacuum Tower Telescope. The spatial scanning of the solar disk covered 11 heliocentric positions each along four radial (meridional and equatorial) axes. The high-resolution spectra of 26 photospheric to chromospheric lines in the visible range were calibrated with a laser frequency comb to absolute wavelengths at the 1m/s accuracy. Applying ephemeris and reference corrections, the bisector analysis provided line asymmetries and Doppler shifts with an uncertainty of only few m/s. To allow for a comparison with other observations, we convolved the results to lower spectral resolutions.
46. Dark-floored pits in Sputnik Planitia on Pluto
ID:
ivo://CDS.VizieR/J/AJ/162/207
Title:
Dark-floored pits in Sputnik Planitia on Pluto
Short Name:
J/AJ/162/207
Date:
02 Feb 2022 06:18:01
Publisher:
CDS
Description:
Sputnik Planitia, Pluto's gigantic, volatile ice glacier, hosts numerous scientific mysteries, including the presence of thousands of elongated pit structures. We examine various attributes of these pit structures in New Horizons data sets, revealing their length, aspect ratio, and orientation properties; we also study their reflectivities, colors, and compositions, and compare these attributes to some other relevant regions on Pluto. We then comment on origin mechanisms of the pits and also the fate of the missing volatiles represented by the pits on Sputnik Planitia. From a sample of 317 pits, we find typical length/width ratios of 2-4, with their major axis preferentially oriented approximately north-south. We also find that the floors of large pits in our sample have similar single-scattering albedos and colors to dark material on crater rims and floors (i.e., possible subsurface windows) in Burney basin. We also find that the base of the three pits in our sample, large enough to study with LEISA IR spectroscopy, display both CH_4_ and N_2_ absorption features, as do the dark regions in crater windows in Burney basin. Evidence for a sublimation erosion origin for the pits is supported over both the explosion/ejecta venting and structural collapse alternatives. Finally, we find that the mass lost by the pits on Sputnik Planitia most likely lies condensed elsewhere, on Pluto's surface, relocated there by volatile transport as opposed to removal by escape to space or photochemical conversion.
47. Dark spots on Neptune from 25 years of HST images
ID:
ivo://CDS.VizieR/J/AJ/157/152
Title:
Dark spots on Neptune from 25 years of HST images
Short Name:
J/AJ/157/152
Date:
21 Oct 2021
Publisher:
CDS
Description:
We scoured the full set of blue-wavelength Hubble Space Telescope images of Neptune, finding one additional dark spot in new Hubble data beyond those discovered in 1989, 1994, 1996, and 2015. We report the complete disappearance of the SDS-2015 dark spot, using new Hubble data taken on 2018 September 9-10, as part of the Outer Planet Atmospheres Legacy (OPAL) program. Overall, dark spots in the full Hubble data set have lifetimes of at least one to two years, and no more than six years. We modeled a set of dark spots randomly distributed in time over the latitude range on Neptune that is visible from Earth, finding that the cadence of archival Hubble images would have detected about 70% of these spots if their lifetimes are only one year, or about 85%-95% of simulated spots with lifetimes of two or more years. Based on the Hubble data set, we conclude that dark spots have average occurrence rates of one dark spot every four to six years. Many numerical models to date have simulated much shorter vortex lifetimes, so our findings provide constraints that may lead to improved understanding of Neptune's wind field, stratification, and humidity.
48. Database of the orbital elements of comets
ID:
ivo://CDS.VizieR/B/comets
Title:
Database of the orbital elements of comets
Short Name:
B/comets
Date:
21 Oct 2021
Publisher:
CDS
Description:
comets.dat is an ASCII file of cometary orbital elements prepared at the "Institut de Mecanique Celeste et de Calcul des Ephemerides" (related to the Bureau des Longitudes, Paris). The research and computing needed to generate comets.dat are funded by the French Ministry of Education. The data can be freely used, provided that their origin (Bureau des longitudes) and the author (P. Rocher) are properly cited. User feed-back is encouraged. Unless otherwise specified, send comments and bug reports to: E-mail : stc@imcce.fr Fax : (33) 1 46 33 28 34 Postal mail : IMCCE - Observatoire de Paris 77 avenue Denfert Rochereau F-75014 PARIS
49. Disk-resolved photometric properties of Pluto
ID:
ivo://CDS.VizieR/J/AJ/159/74
Title:
Disk-resolved photometric properties of Pluto
Short Name:
J/AJ/159/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
A multiwavelength regionally dependent photometric analysis of Pluto's anti-Charon-facing hemisphere using images collected by New Horizons' Multispectral Visible Imaging Camera (MVIC) reveals large variations in the absolute value and spectral slope of the single-scattering albedo. Four regions of interest are analyzed: the dark equatorial belt, Pluto's north pole, nitrogen-rich regions, and the mid-latitude terrains. Regions dominated by volatile ices such as Lowell Regio and Sputnik Planitia present single-scattering albedos of ~0.98 at 492nm, almost neutral across MVIC's visible wavelength range (400-910nm), indicating limited contributions from tholin materials. Pluto's dark equatorial regions, informally named Cthulhu and Krun Maculae, have single-scattering albedos of ~0.16 at 492nm and are the reddest regions. Applying the Hapke radiative transfer model to combined MVIC and Linear Etalon Imaging Spectral Array (LEISA) spectra (400-2500nm) of Cthulhu Macula and Lowell Regio successfully reproduces the spectral properties of these two regions of dramatically disparate coloration, composition, and morphology. Since this model uses only a single coloring agent, very similar to the Titan like tholin of Khare+ (1984Icar...60..127K), to account for all of Pluto's colors, this result supports the Grundy+ (2016Sci...351.9189G) conclusion that Pluto's coloration is the result of photochemical products mostly produced in the atmosphere. Although cosmic rays and extreme ultraviolet photons reach Pluto's surface where they can drive chemical processing, observations of diverse surface colors do not require different chemical products produced in different environments. We report a correction scaling factor in the LEISA radiometric calibration of 0.74{+/-}0.05.
50. Distribution of ^26^Al in the solar system
ID:
ivo://CDS.VizieR/J/ApJ/733/L31
Title:
Distribution of ^26^Al in the solar system
Short Name:
J/ApJ/733/L31
Date:
21 Oct 2021
Publisher:
CDS
Description:
It is believed that ^26^Al, a short-lived (t_1/2_=0.73Ma) and now extinct radionuclide, was uniformly distributed in the nascent solar system (SS) with the initial ^26^Al/^27^Al ratio of ~5.2x10^-5^, suggesting an external, stellar origin rather than local, solar source. However, the stellar source of ^26^Al and the manner in which it was injected into the SS remain controversial: the ^26^Al could have been produced by an asymptotic giant branch star, a supernova, or a Wolf-Rayet star and injected either into the protosolar molecular cloud, protosolar cloud core, or protoplanetary disk. Corundum (Al_2_O_3_) is predicted to be the first condensate from a cooling gas of solar composition. Here we show that micron-sized corundum condensates from ^16^O-rich ({Delta}^17^O~-25%) gas of solar composition recorded heterogeneous distribution of ^26^Al at the birth of the SS: the inferred initial ^26^Al/^27^Al ratio ranges from ~6.5x10^-5^ to <2x10^-6^; 52% of corundum grains measured are ^26^Al-poor. Abundant ^26^Al-poor, ^16^O-rich refractory objects include grossite- and hibonite-rich calcium-aluminum-rich inclusions (CAIs) in CH (high metal abundance and high iron concentration) chondrites, platy hibonite crystals in CM (Mighei-like) chondrites, and CAIs with fractionation and unidentified nuclear effects CAIs chondrites. Considering the apparently early and short duration (<0.3Ma) of condensation of refractory ^16^O-rich solids in the SS, we infer that ^26^Al was injected into the collapsing protosolar molecular cloud and later homogenized in the protoplanetary disk. The apparent lack of correlation between ^26^Al abundance and O-isotope composition of corundum grains constrains the stellar source of ^26^Al in the SS.