A LAMBDA-3.6 CM RADIO SURVEY OF LOW-MASS, WEAK-LINE T-TAURI STARS IN TAURUS-AURIGA

We report on the results of a sensitive survey for lambda 3.6 cm radio emission from low-mass, weak T Tauri (WTT) stars in the Taurus-Auriga cloud complex. Targets are stars in the Herbig and Bell Catalog (Herb ig & Bell 1988) of spectral type K7 or later, and equivalent width of the H alpha emission line less than 10 Angstrom. Of the 28 such stars surveyed using the Very Large Array down to detection thresholds of si milar to 0.1 mJy, 7 (possibly 8) are observed to emit at strengths ran ging from 0.1 to 2 mJy. Five young radio stars are newly discovered in our survey: V827 Tau and V710 Tau B are relatively strong sources of mJy emission, while IW Tau, UX Tau B, and the possible detection LkHa 332-G1 form a new population of relatively weak emitters. Our radio su rvey and complementary surveys are pooled, and of 42 WTT stars K7 or l ater in Tau-Aur, 13 are now known to be radio emitters at lambda 6 and lambda 3.6 cm. Statistical tests to measure the degree of association between radio luminosity and other stellar attributes have been carri ed out. Wide binarity (component separations in excess of 0''.13, 18 A U) appears unrelated to radio emission, as does spectral type. In addi tion, in contrast to previous work by other workers, we find the radio -detected and radio-undetected stars to be distributed similarly in th e Tau-Aur CO cloud. However, we find positive, albeit somewhat weak as sociations between detectable radio luminosity and (1) relatively low H alpha emission and (2) relatively young ages as measured on the Hert zprung-Russell (H-R) diagram. Theoretical isochrones on the H-R diagra m yield a difference in mean ages of 0.7 Myr between radio-detected an d radio-undetected populations, and the distributions of ages of the t wo populations suggest that the mechanism driving the nonthermal radio emission (thought to involve globally ordered and exceptionally stron g magnetic fields) operates over times less than or similar to 1 Myr d uring a relatively early phase of pre-main-sequence evolution. (C) 199 6 American Astronomical Society.