Correlations of Spectral Accretion Signatures in Young Binaries

Abstract

We review correlations of spectral accretion diagnostics in young binary star systems. Hydrogen emission lines at visual (Hα) and near-infrared (Brγ) wavelengths indicate the presence of active accretion flows onto young stars. We examine the simultaneity of this process in both components of close binaries (separations 100–1500 AU) and find that active accretion is not a random process in these systems: the two stars are typically both active or both inactive. Only 19% of our sample consists of mixed pairs in which just one component displays evidence of accretion, usually the primary. In systems with two active stars, the equivalent width and in particular the line flux of the primary star is generally dominant, indicating stronger accretion activity. We discuss accretion and disk dissipation processes in close binaries and propose that a circumbinary envelope model accounts for the correlated evolution of circumstellar disks around young binaries.