Accretion properties of T Tauri stars in \sigma Orionis
T. Gatti, A. Natta, S. Randich, L. Testi, ; G. Sacco ; - ASI Sponsor
Jan - 2008

journal : A\&A

Issue : 2
type: Article Journal

Abstract
Accretion disks around young stars evolve in time with time scales of a few million years. We present here a study of the accretion properties of a sample of 35 stars in the \\backslash sim \3 million-year-old star-forming region \\backslash sigma\ Ori. Of these, 31 are objects with evidence of disks, based on their IR excess emission. We use near-IR hydrogen recombination lines (Pa\\backslash gamma\) to measure their mass accretion rate. We find that the accretion rates are significant lower in \\backslash sigma\ Ori than in younger regions, such as \\backslash rho\ Oph, consistently with viscous disk evolution. The He I 1.083 \\backslash mu \m line is detected (either in absorption or in emission) in 72\% of the stars with disks, also providing evidence of accretion-powered activity in very low accretors, where other accretion indicators disappear.

keywords : ASI - Sponsor