MAGNETOSPHERIC ACCRETION AND PRE-MAIN-SEQUENCE STELLAR MASSES

We present a method of determining lower limits on the masses of pre-m ain-sequence (PMS) stars and so constraining the PMS evolutionary trac ks. This method uses the redshifted absorption feature observed in som e emission-line profiles of T Tauri stars, indicative of infall, The m aximum velocity of the accreting material measures the potential energ y at the stellar surface, which, combined with an observational determ ination of the stellar radius, yields the stellar mass. This estimate is a lower limit owing to uncertainties in the geometry and projection effects. Using available data, we show that the computed lower limits can be larger than the masses derived from PMS evolutionary tracks fo r M less than or similar to 0.5 M-.. Our analysis also supports the no tion that accretion streams do not impact near the stellar poles but p robably hit the stellar surface at moderate latitudes.