First Overtone CO Bands in the Giant Component of RS Ophiuchi: the 12C/13C Ratio in 2008

TL;DR

This study analyzes high-resolution infrared spectra of RS Ophiuchi's secondary star to determine the 12C/13C ratio, providing insights into its evolutionary stage as a red giant beyond the first dredge-up phase.

Contribution

First measurement of the 12C/13C ratio in RS Oph's secondary star using high-resolution spectra, indicating its advanced evolutionary status.

Findings

12C/13C ratio is 16 +/- 3

Secondary is a red giant beyond the first dredge-up

Spectral analysis confirms stellar evolutionary stage

Abstract

We present an analysis of a high resolution (R = 40000) infrared spectrum of the RS Oph secondary around the first overtone CO bands, obtained in 2008 May on the Gemini South 8 m. 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 red giant which has evolved beyond the first drege-up phase of evolution.