8.1um SiO spectra of cool evolved stars

The SiO fundamental lines near 8 m are potentially useful for probing the outer atmosphere, which is essential for clarifying the mass-loss mechanism. However, these lines have been little explored until now.

We present high spectral resolution spectroscopic observations of the SiO fundamental lines near 8.1um in 16 bright red giants and red supergiants. Our sample consists of seven normal (i.e., non-Mira) K-M giants (from K1.5 to M6.5), three Mira stars, three optically bright red supergiants, two dusty red supergiants, and the enigmatic object GCIRS3 near the Galactic center.