New "weak-line"-T Tauri stars in Lupus

Abstract

We present first results obtained by a survey of the Lupus star forming region in search of new T Tauri stars. This study has been performed on the basis of deep pointed ROSAT observations in the Lupus dark clouds as well as data from the ROSAT All-Sky-Survey in the surrounding, less obscured regions. Our survey covers an area of about 230 square degrees, located between 15h 6m and 16h 24m in right ascension and between -47° and -32° in declination. Identification of ROSAT All-Sky-Survey sources in this area by means of optical spectroscopy revealed 89 T Tauri stars, 86 of them "weak-line" T Tauri stars (WTTS) not known from previous studies of this region. Our pointed ROSAT observations led to the identification of 47 more T Tauri stars, giving a total of 136 new T Tauri stars. The large area of our study, as compared with previous works, allows us to study the spatial distribution of WTTS in this star forming region on a large scale. We find the new WTTS to be distributed over the whole area of our survey, indicating that their spatial distribution might extend well beyond our study area. Contrary to the Lupus T Tauri stars known prior to this study, the WTTS discovered by the ROSAT All-Sky-Survey are not clustered in the regions of highest extinction, i.e. the dark clouds.