A new IR study of intrinsic and extrinsic S-type stars

Then we look for the diagnosis to extract intrinsic S-type stars from the large unclassified sample. We found that, statistically, intrinsic S-type stars have larger infrared excesses than extrinsic S-type stars in the wavelength region of 1-60 {mu}m due to thicker dusty circumstellar envelopes.

We also found that only intrinsic S-type stars occupy the reddest color areas in all of the two-color diagrams we presented. Finally, 172 new intrinsic S-type stars are presented in this paper. This makes the number of known intrinsic S-type stars almost double.