Strategy of Infrared Surveys for Studying Galactic Evolved Stars and Their Subclasses

Abstract

Concerning the separation of disk Miras and Semiregular variables using just DENIS and IRAS data I refer to the paper by Hron & Kerschbaum in this volume. For those stars for which at least IRAS 12µm fluxes are available, (K-[12]) is a good selection criterion, otherwise (I-K) is reasonably useful. Contamination by the expected large number of M dwarfs should not be a problem because these stars will be found at much fainter K magnitudes than the galactic AGB stars. However, the bluest of the AGB variables will be indistinguishable from the non-variable M giants, both in their colours and their apparent magnitudes. (H-K) should probably allow a good distinction between Miras and Semiregulars (see e.g. Kerschbaum & Hron, A&A in press), even if one considers the scatter in this colour index due to variability.