ROSAT X-RAY-DETECTION OF EPSILON TAURUS - REVISITING THE CORONAL AND TRANSITION REGION EMISSION OF THE HYADES GIANTS

We report on a recent pointed X-ray observation of the Hyades giant epsilon Tau, obtained with the ROSAT PSPC. We confirm at higher significance the earlier ROSAT all-sky survey detection of this star, with an X-ray luminosity of approximately 10(28) ergs s-1. Epsilon Tau turns out to be the X-ray faintest among the four giants of the Hyades cluster, and the only one with no evidence of binarity. We rediscuss possible explanations, already put forward in previous studies, for the large spread in coronal and transition region emission observed among these stars. We revisit this issue in the light of our most recent knowledge on X-ray and UV emission properties of other Hyades and field stars.