Classification of EUV stellar sources detected by the ROSAT WFC^*,**

I. Photometric and radial velocity studies

¹ Catania Astrophysical Observatory, V.le A. Doria 6, I-95125 Catania, Italy
² Brera Astronomical Observatory, Via Bianchi 46, I-22055 Merate, Italy
³ Institute of Astronomy, Catania University, V.le A. Doria 6, I-95125 Catania, Italy
⁴ Palermo Astronomical Observatory, P.zza del Parlamento 1, I-90134 Palermo, Italy

Send offprint request to: G. Cutispoto

Received: 2 March 1999
Accepted: 19 May 1999

Abstract

We present the results of high-precision photometric observations and of spectroscopic radial velocity measurements obtained at the European Southern Observatory for a sample of 51 cool stars detected in the EUV by the ROSAT Wide Field Camera (WFC). Using also recent results from HIPPARCOS, we infer spectral types and investigate the single or binary nature of the sample stars. Optical variability, with periods in the 0.4-13 day range, has been detected for the first time in 15 of these stars.