Photometric and spectroscopic follow-up of optical counterparts of X-ray sources in the RasTyc sample

Abstract The cross-correlation between the ROSAT all-sky survey (∼ 150000 sources)and the Tycho mission (∼ 1000000 stars) catalogs has selected about 14000stellar X-ray sources (RasTyc sample, Guillout et al. 1999).About 200-300 stars have been spectroscopically observed at high resolutionboth in the Hα and Liiλ6708 regions with Elodieand Aureliespectrographsof the OHP (Observatoire de l’Haute Provence, France). The aim was to classifythe RasTyc star sample in terms of age and chromospheric activity level and todetect eventual binary systems.Photometric and spectroscopic follow-up observations of aRasTyc sub-samplecomposed of particularly interesting objects (binaries and very young stars) hasbeen performed with the 91-cm telescope of the Catania Astrophysical Observa-tory.In this work we present some results of this monitoring. In particular, wehave obtained good radial velocity curves and solved for the orbits of three SB2and three SB1 spectroscopic binaries. In addition, for near all sources we havedetected a photometric modulation ascribable to photospheric surface inhomo-geneities and chromospheric Hα line variation.Keywords: Stars: binaries: spectroscopic, Stars: fundamental parameters, Stars: X-ray,Stars: activity