Optical Forbidden Emission Line Spectro-astrometry of T CrA: Evidence for a Multiple System and Multiple Jets* * Based on data collected by UVES 089.C-0299(A) observations at the VLT on Cerro Paranal (Chile), which is operated by the European Southern Observatory (ESO).

Abstract

Spectro-astrometry is applied to echelle spectra of the young intermediate-mass star T CrA. The aim is to better understand the origin of the [O i] and [S ii] emission from T CrA and further explore the usefulness of spectro-astrometry in the search for a reliable tracer of MHD disk winds. The analysis reveals a small-scale curved jet in an east–west direction and inclined parallel to the plane of the sky. It is the inclination of this jet that led to the classification of the forbidden emission lines as a low-velocity component. Thus, spectro-astrometry highlights here that for close to edge-on disks spatial information is necessary. The position angle of the jet is not perpendicular to the position angle of the accretion disk nor does it agree with older observations of outflows likely driven by T CrA. The mass outflow rate of 5–10 × 10−8 M ⊙ yr−1 is within the range for intermediate-mass stars. We conclude that more than one outflow is driven by the T CrA system and that the curvature seen in the first detection of an outflow from T CrA and in the data presented here is likely due to the multiplicity of the system.