Uncovering the Outflow Driven by the Brown Dwarf LS - RCrA 1 : H α as a Tracer of Outflow Activity in Brown Dwarfs

It is now apparent that classical T Tauri-like outflows commonly accompany the formation of young brown dwarfs. To date two optical outflows have been discovered and results presented in this paper increase this number to three. Using spectro-astrometry the origin of the LS-RCrA 1 forbidden emission lines in a blue-shifted outflow is confirmed. The non-detection of the red-shifted component of the outflow in forbidden lines, along with evidence for some separation between low and high velocity outflow components, do not support the hypothesis that LS-RCrA 1 has an edge-on accretion disk. The key result of this analysis is the discovery of an outflow component to the Hα line. The Hα line profile has blue and red-shifted features in the wings which spectro-astrometry reveals to also originate in the outflow. The discovery that Hα emission in BDs can have a significant contribution from an outflow suggests the use of Hα line widths as a proxy of mass accretion in BDs is not clear-cut. This method assumes that any contribution to the Hα line flux from a possible outflow is negligible. Finally the fact that the Hα line traces both lobes of the outflow while only the blue-shifted lobe is seen in forbidden emission points to the presence of a dust hole in the accretion disk of LS-RCrA 1. This is commonly seen in CTTSs and is assumed to signal the onset of planet formation. Based on data collected by UVES observations (observing runs 67.C-0549(B), 69.B-0126(A), 71.C0429(C) and 71.C-0429(D)) at the VLT on Cerro Paranal (Chile) which is operated by the European Southern Observatory (ESO). School of Cosmic Physics, Dublin Institute for Advanced Studies Osservatorio Astrofisico di Arcetri ar X iv :0 90 1. 04 65 v1 [ as tr oph .S R ] 5 J an 2 00 9