2006AJ....132.1468Y

We attempt to select new candidate intrinsic and extrinsic S stars in the General Catalogue of Galactic S Stars (GCGSS) by combining data from the Two Micron All Sky Survey, the Infrared Astronomical Satellite, and the Midcourse Space Experiment. Catalog entries are cross-identified, yielding 528 objects, out of which 29 are known extrinsic S stars and 31 are known intrinsic S stars. Their color-color diagrams, (H-[12])-(K-[12]) and (K-[12])-(J-[25]), are drawn and used to identify a new sample of 147 extrinsic and 256 intrinsic S star candidates, while the nature of 65 stars remains identified. We infer that about 38%±10% of the GCGSS objects are of extrinsic type. Moreover, we think that colors such as J-[25] can be used to split off the two categories of S stars, while single colors are not appropriate. The color-color diagrams, such as (H-[12])-(K-[12]) and (K-[12])-(J-[25]), are proven to be powerful tools for distinguishing the two kinds of S stars.