Studying the Cooolest Giant Stars at Milliarcsecond Resolution

Abstract

Measurements of the angular diameters, surface structure and near-stellar environment of late-type stars have been until now one of the major applications for a wide variety of high angular resolution techniques, and they will probably remain one of the priorities for the VLTI. The proposed angular resolution and sensitivity of the VLTI, as well as the wavelength coverage of its first generation instruments, match quite well those presently achieved by the technique of lunar occultations. Given the premium on VLTI time, it is useful to explore the possibilities opened by coordinated observations in which the VLTI is used to follow up interesting sources previously discovered by lunar occultations. We will review the current status of high angular resolution investigations of cool giant stars, and the impact that the VLTI could have in this field. In particular, attention is given to the coolest spectral types, below M5.