Detection of Disk Accretion at the Substellar Limit

Abstract

We have made the first definitive detection of disk accretion in an object near or below the substellar limit. We obtained an echelle-resolution spectrum of the very low mass T Tauri star V410 Anon 13; the emission-line profile of Ha clearly exhibits the large line width and asymmetry characteristic of a free-falling accretion flow. We use magnetospheric accretion models of the line profile to estimate the mass accretion rate in this object, which is the smallest yet determined. We further augment this with models of the accretion shock and disk to explain the absence of both optical veiling and an infrared excess, obtaining a firm upper limit to the accretion rate that is consistent with the Ha model. Our results indicate that disk accretion via magnetospheric infall occurs even in the lowest mass young objects.