J/A+A/619/A127 Comet C/2016 R2 (PanSTARRS) IRAM spectra (Biver+, 2018)
The extraordinary composition of the blue comet C/2016 R2 (PanSTARRS).
Biver N., Bockelee-Morvan D., Paubert G., Moreno R., Crovisier J.,
Boissier J., Bertrand E., Boussier H., Kugel F., McKay A., Dello Russo N.,
DiSanti M.A.
<Astron. Astrophys. 619, A127 (2018)>
=2018A&A...619A.127B 2018A&A...619A.127B (SIMBAD/NED BibCode)
ADC_Keywords: Comets ; Radio lines ; Carbon monoxide ; Line Profiles ;
Abundances ; Spectroscopy
Keywords: comets: general - comets: individual: C/2016 R2 -
submillimeter: planetary systems - radio lines: planetary systems
Abstract:
We present a multi-wavelength study of comet C/2016 R2 (PanSTARRS).
This comet was observed on 23-24 January 2018 with the IRAM 30m
telescope, and in January to March 2018 with the Nancay radio
telescope. Visible spectroscopy was performed in December 2017 and
February 2018 with small amateur telescopes. We report on measurements
of CO, CH3OH, H2CO and HCN production rates, and on the
determination of the N2/CO abundance ratio. Several other species,
especially OH, were searched for but not detected. The inferred
relative abundances, including upper limits for sulfur species, are
compared to those measured in other comets at about the same
heliocentric distance of ∼2.8AU. The coma composition of comet
C/2016 R2 is very different from all other comets observed so far,
being rich in N2 and CO and dust poor. This suggests that this comet
might belong to a very rare group of comets formed beyond the N2 ice
line. Alternatively, comet C/2016 R2 (PanSTARRS) could be the fragment
of a large and differentiated transneptunian object, with properties
characteristic of volatile-enriched layers.
Description:
Spectra of comet C/2016 R2 (PanSTARRS) obtained with the IRAM-30m
radio telescope with either the FTS spectrometer (r2f*****.fit) with a
0.1953125 MHz spectral sampling or the VESPA autocorrelator
(r2v*****.fit) with spectral sampling of of 0.01953125 to 1.250 MHz.
First 8 spectra are the full spectroscopic range of the spectra
presented in Figs. 3 to 8. Note that r2ffig08.fit is an average of two
lines of CO+ at different frequencies, aligned according to their
Doppler velocity. The frequency scale is relevant to one of the lines.
The next 112 spectra are the daily average of each spectrum: same
frequency range and day of acquisition. They are averages of the two
orthogonal polarisations spectra and selected position offsets
centered on the comet (offset larger than the 4-5" used for mapping
excluded). These were used to build table 5.
The last set of 26 spectra (9+7+10) "r2map***.fit" correspond to the
VESPA spectra of CO(2-1) from the three small maps, like the one
(map3) presented in Figure 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 224 146 List of fits spectra
fits/* . 146 Individual fits spectra
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 24 I5 --- Nx Number of pixels along X-axis
26- 48 A23 "datime" Obs.Date Observation date (YYYY/MM/DDThh:mm:ss.sss)
50- 61 E12.6 Hz bFreq Lower value of frequency interval
63- 73 E11.6 Hz BFreq Upper value of frequency interval
75- 82 E8.3 Hz dFreq Frequency resolution
84- 85 I2 Kibyte size Size of FITS file
87- 98 A12 --- FileName Name of FITS file, in subdirectory fits
100-153 A54 --- Title Title of the FITS file
155-224 A70 --- Com Comments
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Acknowledgements:
Nicolas Biver, nicolas.biver(at)obspm.fr
(End) Nicolas Biver [LESIA, Paris Obs.], Patricia Vannier [CDS] 21-Sep-2018