Timescale of mass accretion in pre-main-sequence stars

Abstract

We present the initial result of a large spectroscopic survey aimed at measuring the timescale of mass accretion in young, pre-mainsequence stars in the spectral type range K0-M5. Using multi-object spectroscopy with VIMOS at the VLT we identified the fraction of accreting stars in a number of young stellar clusters and associations of the ages of between 1-30 Myr. The fraction of accreting stars decreases from ∼60% at 1.5-2 Myr to ∼2% at 10 Myr. No accreting stars are found after 10 Myr at a sensitivity limit of 10 -11 M⊙ yr-1. We compared the fraction of stars showing ongoing accretion ( facc) to the fraction of stars with near-to-mid infrared excess ( fIRAC). In most cases we find f acc