The Detection of Infrared SiS Bands in Spectra of S Stars
Cami, J × Sloan, G. C Markwick-Kemper, A. J Zijlstra, Albert A Bauschlicher, C. W Matsuura, M Decin, Leen Hony, S #
I O P Publishing Ltd.
The Astrophysical Journal. Letters vol:690 issue:2 pages:L122-L125
We present Spitzer spectra of S stars, which are cool evolved stars with a C/O ratio near unity, some of which have enhanced s-process abundances. We present the detection of a strong and unusual band in themid- infrared, at 13 mu m, within the N-band window. Using quantum-chemically calculated line lists, and model spectra, we identify this band as the fundamental rovibrational band of SiS. Detection of the overtone band at 6.7 mu m confirms the identification. Fitting the line profile shows that the molecule is located in relatively cool layers, at T similar to 1500 K. We discuss these results in the context of chemical equilibrium models. The observed strength of these bands in the cool S stars makes them a promising observational diagnostic tool for studying the atmospheres of brown dwarfs and exoplanets.