Pavlenko, Ya. V., Woodward, Charles E., Rushton, M. T., Kaminsky, B. and Evans, A.
First overtone CO bands in the giant component of RS Ophiuchi: the12C/13C ratio in 2008.
Monthly Notices of the Royal Astronomical Society, 404
We present an analysis of a high-resolution (R≃ 40 000) infrared spectrum of the RS Oph secondary around the first overtone CO bands, obtained in 2008 May on the Gemini-South 8 m telescope. The 12CO and 13CO bands are well resolved, and we compute synthetic spectra to determine the 12C/13C ratio. We find 12C/13C ≃ 16 ± 3, consistent with the interpretation of the secondary as a red giant which has evolved beyond the first dredge-up phase of evolution.