Magnetospheric accretion and pre-main-sequence stellar masses

I. A. Bonnell, K. W. Smith, M. R. Meyer, C. A. Tout, D. F. M. Folha, J. P. Emerson

Abstract
We present a method of determining lower limits on the masses of pre-main-sequence (PMS) stars and so constraining the PMS evolutionary tracks. This method uses the redshifted absorption feature observed in some emission-line profiles of T Tauri stars, indicative of infall. The maximum velocity of the accreting material measures the potential energy at the stellar surface, which, combined with an observational determination 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 for M≤0.5M_o. Our analysis also supports the notion that accretion streams do not impact near the stellar poles but probably hit the stellar surface at moderate latitudes.

Monthly Notices of the Royal Astronomical Society
Volume 299, Page 1013
October 1998