Dynamical Evidence for a Magnetocentrifugal Wind from a 20 Msun Binary Young Stellar Object
Abstract
In Orion BN/KL, proper motions of 7 mm vibrationally-excited SiO masers trace rotation of a nearly edge-on disk and a bipolar wide-angle outflow 10-100 AU from radio Source I, a binary young stellar object (YSO) of ~20 Msun. Here we map ground-state 7 mm SiO emission with the Very Large Array and track proper motions over 9 years. The innermost and strongest emission lies in two extended arcs bracketing Source I. The proper motions trace a northeast-southwest bipolar outflow 100-1000 AU from Source I with a median 3D motion of ~18 km/s. An overlying distribution of 1.3 cm H2O masers betrays similar flow characteristics. Gas dynamics and emission morphology traced by the masers suggest the presence of a magnetocentrifugal disk-wind. Reinforcing evidence lies in the colinearity of the flow, apparent rotation across the flow parallel to the disk rotation, and recollimation that narrows the flow opening angle ~120 AU downstream. The arcs of ground-state SiO emission may mark the transition point to a shocked super-Alfvenic outflow.
Cite
@article{arxiv.1305.4150,
title = {Dynamical Evidence for a Magnetocentrifugal Wind from a 20 Msun Binary Young Stellar Object},
author = {L. J. Greenhill and C. Goddi and C. J. Chandler and L. D. Matthews and E. M. L. Humphreys},
journal= {arXiv preprint arXiv:1305.4150},
year = {2015}
}
Comments
7 pages, 4 figures, and 1 table. Accepted for publication in ApJ Letters