Newly discovered candidate weak-line T Tauri stars in the surrounding area of the Taurus-Auriga region

Abstract

We present results of an extensive search for weak-line T Tauri stars (WTTS) in the outskirts of the Taurus-Auriga molecular cloud on the basis of the ROSAT All-Sky Survey Bright Source Catalog. Our surveyed region extends from 2h 40m to 5h 40m in right ascension and from 10° to 40° in declination, with the central part of Taurus-Auriga (4 5h , 15 34°), accomplished by Wichmann et al. (1996), excluded. Within a sky coverage of about 103 square degrees, 219 X-ray sources fulfil the criteria for selecting program sources suggested by Neuhauser et al. (1995a), and 164 of these X-ray sources were found to have at least one optical counterpart with E magnitude brighter than 16. Low-resolution spectroscopic observation has been carried out in order to discard early type stars and galaxies from the sample, additional intermediate-resolution spectra of a sub-sample of 156 late type optical counterparts were obtained for spectral classification and for the calculation of the equivalent width of H emission and LiI line absorption at 6707 A. Excluding 2 previously identified WTTS, a total of 75 new candidate WTTS and one possible classical T Tauri star have been discovered in our study. The majority of the newly found Li-rich optical counterparts are believed to be PMS stars rather than ZAMS stars as those of the Pleiades.