UV survey of δ Scuti stars: Final results and open problems

Abstract

The results obtained from our IUE observations of some δ Scuti stars and in particular 71 Tau and 69 Tau are reviewed. 71 Tau is the second brightest X-ray source of the Hyades cluster; on the contrary 69 Tau, very similar to 71 Tau in the optical range, does not show X emissions. The complex and in somewhat controversial scenario obtained from this survey is also discussed. In particular we consider the X-ray emission detected in some δ Scuti with respect to the chromospheric activity level as measured through the MgII line and to other stellar parameters.