Issue |
A&A
Volume 683, March 2024
|
|
---|---|---|
Article Number | A50 | |
Number of page(s) | 11 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202348027 | |
Published online | 05 March 2024 |
12CO+ and 13CO+ fluorescence models for measuring the 12C/13C isotopic ratio in comets
1
Institut UTINAM – UMR 6213, CNRS / Univ. de Franche-Comté, OSU THETA, 41 bis Av. de l’Observatoire, BP 1615, 25010 Besançon Cedex, France
e-mail: philippe.rousselot@obs-besancon.fr
2
STAR Institute, Univ. of Liège, Allée du 6 Août 19c, 4000 Liège, Belgium
3
Institute for Astronomy, Univ. of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
4
Laboratoire Interdisciplinaire Carnot de Bourgogne – UMR 6303, CNRS / Univ. de Bourgogne, 9 Av. A. Savary, BP 47870, 21078 Dijon Cedex, France
Received:
20
September
2023
Accepted:
1
December
2023
Context. CO is an abundant species in comets, creating CO+ ion with emission lines that can be observed in the optical spectral range. A good modeling of its fluorescence spectrum is important for a better measurement of the CO+ abundance. Such a species, if abundant enough, can also be used to measure the 12C/13C isotopic ratio.
Aims. This study uses the opportunity of a high CO content observed in the comet C/2016 R2 (PanSTARRS), which created bright CO+ emission lines in the optical range, to build and test a new fluorescence model of this species and to measure the 12C/13C isotopic ratio in this chemical species for the first time with ground-based observations.
Methods. Thanks to laboratory data and theoretical works available in the scientific literature, we developed a new fluorescence model both for 12CO+ and 13CO+ ions. The 13CO+ model can be used for coadding faint emission lines and to obtain a sufficient signal-to-noise ratio to detect this isotopologue.
Results. Our fluorescence model provides a good modeling of the 12CO+ emission lines, allowing us to publish revised fluorescence efficiencies. Based on similar transition probabilities for 12CO+ and 13CO+, we derive a 12C/13C isotopic ratio of 73±20 for CO+ in comet C/2016 R2. This value is in agreement with the Solar System ratio of 89±2 within the error bars, but is also consistent with the 12C/13C ratio in local interstellar medium (68±15).
Key words: line: identification / molecular data / comets: general / comets: individual: C/2016 R2
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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