AAS 196th Meeting, June 2000
Session 5. Be Star and Other Atmosphere Studies
Display, Monday, June 5, 2000, 9:20am-6:30pm, Empire Hall South

[Previous] | [Session 5] | [Next]

[5.07] MM-VLBI Spectroscopic Imaging of the SiO J=1-0 v=1 and v=2 Masers in M Supergiant VX Sagittarii

A. Fletcher, S. Doeleman, C. Lonsdale (MIT Haystack Observatory)

We present the first simultaneous mm-VLBI observations of two SiO maser transitions of a \Delta\theta = 50 mas square field around the cool M supergiant variable star VX Sagittarii (\Delta{X}= 85 AU at an assumed distance of D = 1.7 kpc). The two transitions imaged with the VLBA on 4 April 1998 are: SiO v=1 J=1-0 at \nu = 43.122 GHz, and SiO v=2 J=1-0 at \nu = 42.821 GHz. The resulting spectral line cubes, with \Delta\theta~.4 mas angular and \Delta{v}~.5 km/s spectral resolutions, will be cross-correlated in both position and velocity in order to determine the degree of overlap between the maser features in each vibrational transition. We find much complex structure, with the maser spots being roughly distributed in a ring-like manner, presumably around VX Sgr itself. The individual components have typical velocity width ~1 km/s, and angular sizes ranging from 0.2 to 0.5 mas along the minor axis of the restoring beam (0.3 to 0.9 AU at 1.7 kpc). Based on the degree of cospatiality between the v=1 and v=2 masers, we discuss the implications for collisional versus radiative pumping models.

This research is funded by the National Science Foundation, under Award #9727353.

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

[Previous] | [Session 5] | [Next]