J/ApJ/889/L30 Opt. spectra of the interstellar object 2I/Borisov (Lin+, 2020)
Detection of diatomic carbon in 2I/Borisov.
Lin H.W., Lee C.-H., Gerdes D.W., Adams F.C., Becker J., Napier K.,
Markwardt L.
<Astrophys. J., 889, L30 (2020)>
=2020ApJ...889L..30L 2020ApJ...889L..30L
ADC_Keywords: Comets; Spectra, optical
Keywords: Comets
Abstract:
2I/Borisov is the first-ever observed interstellar comet (and the
second detected interstellar object (ISO)). It was discovered on
2019 August 30 and has a heliocentric orbital eccentricity of ∼3.35,
corresponding to a hyperbolic orbit that is unbound to the Sun. Given
that it is an ISO, it is of interest to compare its properties-such as
composition and activity-with the comets in our solar system. This
study reports low-resolution optical spectra of 2I/Borisov. The
spectra were obtained by the MDM Observatory Hiltner 2.4m
telescope/Ohio State Multi-Object Spectrograph (on 2019 October 31.5
and November 4.5, UT). The wavelength coverage spanned from 3700 to
9200Å. The dust continuum reflectance spectra of 2I/Borisov show
that the spectral slope is steeper in the blue end of the spectrum
(compared to the red). The spectra of 2I/Borisov clearly show CN
emission at 3880Å, as well as C2 emission at both 4750 and
5150Å. Using a Haser model to covert the observed fluxes into
estimates for the molecular production rates, we find
Q(CN)=2.4±0.2x1024s-1, and Q(C2)=(5.5±0.4)x1023s-1 at
the heliocentric distance of 2.145au. Our Q(CN) estimate is consistent
with contemporaneous observations, and the Q(C2) estimate is
generally below the upper limits of previous studies. We derived the
ratio Q(C2)/Q(CN)=0.2±0.1, which indicates that 2I/Borisov is
depleted in carbon-chain species, but is not empty. This feature is
not rare for the comets in our solar system, especially in the class
of Jupiter-family comets.
Description:
2I/Borisov was observed with the Hiltner 2.4m telescope and the Ohio
State Multi-Object Spectrograph (OSMOS) on 2019 October 31.5 and
November 4.5 UT via the queue observations of MDM Observatory.
On 2019 October 31 UT we obtained 6 exposures and November 4 UT 11
exposures. Each exposure was 300s and obtained with a 3" wide slit.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
coad.dat 30 571 Flattened and coadded Hiltner 2.4m/OSMOS spectra
of 2I/Borisov (Data behind Figure 1)
2i_nov04.dat 28 571 04 November 2019 Hiltner 2.4m/OSMOS spectra
of 2I/Borisov (Data behind Figure 1)
2i_oct31.dat 28 571 31 October 2019 Hiltner 2.4m/OSMOS spectra
of 2I/Borisov (Data behind Figure 1)
s_nov04.dat 27 571 Solar spectrum taken 04 November 2019
s_oct31.dat 27 571 Solar spectrum taken 31 October 2019
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See also:
J/A+A/634/L6 : NIR spectrum of interstellar object 2I/Borisov (Yang+, 2020)
J/ApJ/889/L38 : Opt. spectroscopic investigations of 2I/Borisov (Kareta+, 2020)
Byte-by-byte Description of file: coad.dat
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Bytes Format Units Label Explanations
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1- 6 F6.1 0.1nm lambda [3500/9200] Wavelength in Agstrom units
8- 30 E23.18 cW/m2/nm Flux [-8.5e-16/9.4e-16] Flux
in erg/s/cm2/Å units
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Byte-by-byte Description of file: 2i_nov04.dat 2i_oct31.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm lambda [3500/9200] Wavelength in Agstrom units
6- 28 E23.22 cW/m2/nm Flux Flux in erg/s/cm2/Å units
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Byte-by-byte Description of file: s_nov04.dat s_oct31.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm lambda [3500/9200] Wavelength in Angstrom units
6- 27 E22.21 cW/m2/nm Flux [1.1e-13/3.7e-13] Flux
in erg/s/cm2/Å units
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 16-Jul-2021