2010/11/09 by Ramstedt, S., Schöier, F. L., Olofsson, H.
#FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.1011.2064
The S-type stars are believed to have a C/O-ratio close to unity (within a few percent). They are considered to represent an intermediate evolutionary stage as AGB stars evolve from oxygen-rich M-type stars into carbon stars. As possible transition objects the S-type stars could give important clues to the mass-loss mechanism(s) and to the chemical evolution along the AGB. Using observations of circumstellar radio line emission in combination with a detailed radiative transfer analysis, we have estimated mass-loss rates and abundances of chemically important molecules (SiO, HCN) for a sample of 40 S-type AGB stars. The results will be compared to previous results for M-type and carbon stars.