Volume 643, November 2020
|Number of page(s)||8|
|Section||Letters to the Editor|
|Published online||23 November 2020|
Letter to the Editor
Detection of infrared fluorescence of carbon dioxide in R Leonis with SOFIA/EXES
Molecular Astrophysics Group, Instituto de Física Fundamental, IFF-CSIC, C/ Serrano, 123, 28006 Madrid, Spain
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
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
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.