A Search for Very Low Mass Pre–Main-Sequence Stars in Taurus

Abstract

?????We present the initial results of a deep CCD survey for very low mass pre?main-sequence (PMS) stars in selected fields of the Taurus molecular cloud complex. The results reported herein span a little over half a square degree in the dark clouds L1495, L1529, L1551, and B209. Our survey is complete down to IC ~ 19 at (R - I)C ~ 2.5, which enables us to probe well below the hydrogen burning limit at 1?2 Myr. From follow-up spectroscopic observations we have identified nine new low-mass T Tauri stars (TTSs). A large fraction of the new PMS objects (5/9) have very low masses as inferred from their late spectral types (?M5), and comparison with recent evolutionary tracks and Pleiades brown dwarfs suggests that our M6?M6.5 new TTSs are very young brown dwarfs. Two of the new TTSs may constitute a new, moderately embedded, binary classical T Tauri system. The new young stars represent a ~38% increase in the known PMS population of our survey area and a factor of ~2 increase in the number of known late-type TTSs. In spite of our sensitivity, we detect no young stars with spectral types later than ~M7. Our results illustrate the importance of spectroscopy in eliminating foreground M stars.