AAS 203rd Meeting, January 2004
Session 13 Disks Around Young Stars
Poster, Monday, January 5, 2004, 9:20am-6:30pm, Grand Hall

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[13.09] Rotation of a Water Maser Disk in the Galactic Star-forming Region Cepheus A

H. Beck (Bucknell University), C. Wolfe (Kutztown University), J. Gallimore, M. Thornley (STScI/Bucknell University)

MERLIN observations of water vapor maser emission, taken in May 2000,revealed an elliptical ring of masers (the``R4 ring'') located near the protostar Cepheus A HW2. The doppler kinematics were found to be consistent with rotation and outflow, and comparison with earlier VLBA observations showed evidence for expansion. We present new MERLIN observations of the R4 ring taken two years after the pilot observations. A model projection of the epoch 2000 maser spot distribution agrees well with the observed epoch 2002 spot distribution in spite of the complicating effects of maser variability and a possible overlapping maser arc not directly associated with the ring. The rotation of the maser ring is apparent both in the distribution of doppler velocities and spot proper motions. These new results support the interpretation that the R4 maser source is a 28 AU diameter, shocked ring of (perhaps protoplanetary) material in a disk rotating around a 3 solar mass protostar.

The author(s) of this abstract have provided an email address for comments about the abstract: gallim@stsci.edu

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.