SiO Bands in the Infrared Spectra of Late-Type Stars

Abstract

Abstract—The importance of taking the SiO absorption in the infrared spectrum into account for spectral analysis of late-type stars is demonstrated. The lists of absorption lines of the fundamental SiO system calculated by the group of J. Tennison in the ExoMol project were used. The bands of isotopic molecules ²⁸SiO, ²⁹SiO, and ³⁰SiO were identified in the spectrum of red giant HD 196610 (V*EU Del, spectral class M6 III) taken from the IRTF spectra library. The relative abundance of silicon isotopes in the atmosphere of HD 196610 was estimated by modeling the bands of the first SiO overtone in the stellar spectrum. This abundance turned out to be close (within 3%) to the solar one. At the same time, the carbon isotope ratio ¹²C/¹³C = 6 ± 1 determined by modeling the isotopic components of the first overtone of CO bands suggests that HD 196610 is at an advanced stage of its evolution.