DYNAMICAL EVIDENCE FOR A MAGNETOCENTRIFUGAL WIND FROM A 20 M ☉ BINARY YOUNG STELLAR OBJECT

In Orion BN/KL, proper motions of {lambda}7 mm vibrationally excited SiO masers trace the 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 of {approx}20 M{sub Sun }. Here we map ground-state {lambda}7 mm SiO emission with...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2013-06, Vol.770 (2), p.L32
Main Authors: Greenhill, L. J., Goddi, C., Chandler, C. J., Matthews, L. D., Humphreys, E. M. L.
Format: Article
Language:English
Subjects:
ASTRONOMY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BINARY STARS
GROUND STATES
JETS
MASERS
MICROWAVE RADIATION
MOLECULES
MORPHOLOGY
PHOTON EMISSION
PROPER MOTION
ROTATION
SILICON OXIDES
VIBRATIONAL STATES
WATER
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Summary:In Orion BN/KL, proper motions of {lambda}7 mm vibrationally excited SiO masers trace the 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 of {approx}20 M{sub Sun }. Here we map ground-state {lambda}7 mm SiO emission with the Very Large Array and track proper motions over 9 yr. 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 three-dimensional motion of {approx}18 km s{sup -1}. An overlying distribution of {lambda}1.3 cm H{sub 2}O 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 {approx}120 AU downstream. The arcs of ground-state SiO emission may mark the transition point to a shocked super-Alfvenic outflow.
ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/770/2/L32