J/ApJ/889/L38 Opt. spectroscopic investigations of 2I/Borisov (Kareta+, 2020)
Carbon chain depletion of 2I/Borisov.
Kareta T., Andrews J., Noonan J.W., Harris W.M., Smith N., O'Brien P.,
Sharkey B.N.L., Reddy V., Springmann A., Lejoly C., Volk K., Conrad A.,
Veillet C.
<Astrophys. J., 889, L38 (2020)>
=2020ApJ...889L..38K 2020ApJ...889L..38K
ADC_Keywords: Comets ; Spectra, optical
Keywords: Spectroscopy ; Comets ; Molecular gas ; Abundance ratios
Abstract:
The composition of comets in the solar system comes in multiple groups
thought to encode information about their formation in different
regions of the outer protosolar disk. The recent discovery of the
second interstellar object, 2I/Borisov, allows for spectroscopic
investigations into its gas content and a preliminary classification
of it within the solar system comet taxonomies to test the
applicability of planetesimal formation models to other stellar
systems. We present spectroscopic and imaging observations from 2019
September 20 through October 26 from the Bok, MMT telescope (formerly
the Multiple Mirror Telescope, Mount Hopkins, Arizona), and Large
Binocular Telescopes. We identify CN in the comet's spectrum and set
precise upper limits on the abundance of C2 on all dates in October.
We use a Haser model to convert our integrated fluxes to production
rates and find Q(CN)=(1.1-1.9)*1024mols/s increasing over 2019
October 1 to 26, consistent with contemporaneous observations. We set
our lowest upper limit on a C2 production rate, Q(C2)<1.6*1023mols/s
on 2019 October 10. The measured upper limit ratio for that date
Q(C2)/Q(CN)<0.1 indicates that 2I/Borisov is strongly in the
(carbon-chain) "depleted" taxonomic group if there is any C2
production at all. Most "depleted" comets are Jupiter-family comets
(JFCs), perhaps indicating a similarity in formation conditions
between the most depleted of the JFCs and 2I/Borisov. More work is
needed to understand the applicability of our knowledge of solar
system comet taxonomies onto interstellar objects and we discuss
future work that could help to clarify the usefulness of the approach.
Description:
We observed interstellar comet 2I/Borisov on 2019 September 20 with
the Boller & Chivens spectrograph at the 2.3m Bok telescope (Kitt Peak
National Observatory, Arizona), on 2019 October 1 and 9 with the Blue
Channel spectrograph at the 6.5m MMT telescope (Mount Hopkins,
Arizona), and on 2019 October 10 with MODS on the Large Binocular
Telescope (LBT).
We also imaged Borisov in the Hale-Bopp CN and Sloan r' filters on
2019 October 26 with the 90 Prime imager on the Bok telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 88 5 Observing circumstances for 2I/Borisov
fig1.dat 34 9774 The flux-calibrated and dust-subtracted spectra
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See also:
J/A+A/634/L6 : NIR spectrum of interstellar object 2I/Borisov (Yang+, 2020)
J/ApJ/889/L30 : Opt. spectra of 2I/Borisov (Lin+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Tel Telescope
14- 24 A11 "date" Date Observation date
26- 29 F4.2 au RH [2.23/2.67] Heliocentric distance, RH
31- 34 F4.2 au Delta [2.52/3.25] Geocentric distance, Δ
36- 46 A11 --- Time Time (UTC)
48- 56 A9 --- Airmass Airmass for the start of each exposure
58- 63 A6 s Exp Exposure time
65- 76 A12 --- R R or filter
78- 88 A11 --- Comm Conditions
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Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 "date" Date Observation date (1)
13- 22 E10.4 0.1nm lambda [3500/6500] Wavelength in Angstrom units
24- 34 E11.4 cW/m2/nm Flux [-2.26e-15/2.4e-15] Flux
in erg/s/cm2/Å units (2)
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Note (1): Full observational details for each date available in Table 1.
Note (2): Flux-calibrated but not dust subtracted.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Jul-2021