Astron. Astrophys. Suppl. Ser. 132, 173-179

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

J.Z. Li - J.Y. Hu

Send offprint request: J.Z. Li

Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, China
e-mail: ljz@nova.bao.ac.cn

Received May 5, 1997; accepted April 14, 1998

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 2$^{\rm h}$40$^{\rm m}$ to 5$^{\rm h}$40$^{\rm m}$ in right ascension and from 10$^{\circ}$ to 40$^{\circ}$ in declination, with the central part of Taurus-Auriga (4$^{\rm h}<\alpha<$ 5$^{\rm h}$, 15$^{\circ}<\delta<$ 34$^{\circ}$), 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 Neuhäuser 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$_{\alpha}$ emission and LiI line absorption at 6707 Å. 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.

Key words: stars: formation -- stars: pre-main sequence -- X-ray: stars -- surveys