Observations of the first-overtone silicon monoxide bands in late-type stars.
Abstract
Scans of the spectral region 3.98-4.07 micrometers, which includes the (2, 0) and (3, 1) rotation-vibration bands of silicon monoxide, have been made at a resolution of 5.5 per cm (88 A) in 74 late-type stars with a grating spectrometer and InSb detector. All the M giants and bright giants observed have detectable SiO absorption, and the bands strengthen rapidly with advancing type until at least M6. A similar trend is found in synthetic SiO strengths computed with model atmospheres. The SiO band strength varies considerably among M supergiants of the same spectral type and is strongly time-dependent in Mira variables. Since the observed spectra of even very late M stars and cool stars of type S exhibit the characteristic shape of SiO absorption, it appears that SiO is the dominant absorber in this region in all cool oxygen-rich stars. The highly luminous supergiants S Per and RW Cep may have the SiO bands in emission, while VY CMa, VX Sgr, and NML Cyg have featureless spectra at the resolution employed. Absorption from (Si-29)(O-16) was probably detected in the Mira variable R Cas near minimum light.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1982
- DOI:
- 10.1086/160411
- Bibcode:
- 1982ApJ...262..201R
- Keywords:
-
- Late Stars;
- Molecular Spectra;
- Silicon Oxides;
- Stellar Spectra;
- Stellar Spectrophotometry;
- Absorption Spectra;
- Atmospheric Models;
- Cool Stars;
- Gratings (Spectra);
- Spectral Bands;
- Supergiant Stars;
- Astrophysics