Issue |
A&A
Volume 643, November 2020
|
|
---|---|---|
Article Number | L15 | |
Number of page(s) | 8 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202039547 | |
Published online | 23 November 2020 |
Letter to the Editor
Detection of infrared fluorescence of carbon dioxide in R Leonis with SOFIA/EXES
1
Molecular Astrophysics Group, Instituto de Física Fundamental, IFF-CSIC, C/ Serrano, 123, 28006 Madrid, Spain
e-mail: jpablo.fonfria@csic.es
2
SOFIA-USRA, NASA Ames Research Center, MS 232-12, Moffett Field, CA 94035, USA
3
Physics Dept. – UC Davis, One Shields Ave., Davis, CA 95616, USA
Received:
28
September
2020
Accepted:
3
November
2020
We report on the detection of hot CO2 in the O-rich asymptotic giant branch star R Leo based on high spectral resolution observations in the range 12.8−14.3 μm carried out with the Echelon-cross-Echelle Spectrograph (EXES) mounted on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We found ≃240 CO2 emission lines in several vibrational bands. These detections were possible thanks to a favorable Doppler shift that allowed us to avoid contamination from telluric CO2 features. The highest excitation lines involve levels at an energy of ≃7000 K. The detected lines are narrow (average deconvolved width ≃2.5 km s−1) and weak (usually ≲10% the continuum). A ro-vibrational diagram shows that there are three different populations, warm, hot, and very hot, with rotational temperatures of ≃550, 1150, and 1600 K, respectively. From this diagram, we derived a lower limit for the column density of ≃2.2 × 1016 cm−2. Further calculations based on a model of the R Leo envelope suggest that the total column density can be as large as 7.0 × 1017 cm−2 and the abundance with respect to H2 ≃2.5 × 10−5. The detected lines are probably formed due to the de-excitation of CO2 molecules from high energy vibrational states, which are essentially populated by the strong R Leo continuum at 2.7 and 4.2 μm.
Key words: stars: AGB and post-AGB / stars: individual: R Leo / stars: abundances / circumstellar matter / line: identification / surveys
© ESO 2020
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