AAS 203rd Meeting, January 2004
Session 49 Stars Looking Forward to Retirement
Poster, Tuesday, January 6, 2004, 9:20am-6:30pm, Grand Hall

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[49.07] Interferometric observations of the supergiant S Persei: Evidence for axial symmetry and the warm molecular layer

R.R. Thompson (Jet Propulsion Laboratory), M.J. Creech-Eakman (New Mexico Tech)

We report high-resolution angular size measurements of the supergiant star S Persei using the Palomar Testbed Interferometer (PTI). Observations were conducted in the K-band (2.0-2.4 \mum) between the years 2001 - 2003. For nights with data spanning more than 20 deg in position angle (PA), the normalized visibilities fit a uniformly bright ellipse model (ED) substantially better than a uniformly bright disk model (UD). In each case where the ED model was fit, axial ratios (b/a) ranged from 0.75 - 0.95, and each of the five spectral channels within the K-band follow this trend. The PA of the minor axis (40 deg from North to East) in the continuum and the other four spectral channels all are perpendicular to optical polarization vectors, and parallel to the elongation vectors of the maser outflows. Temporal evolution of the visibilities suggest an axial-symmetric geometry with a dissipating outflow shell. Spectral UD angular diameters show the presence of a detached warm molecular layer (H2O) above the stellar surface, similar to that of evolved oxygen-rich giants stars such as late M-type Mira variables. Stellar parameters based on the mean UD diameters are calculated to be R\star = 1212 /pm 124 R\odot and Teff = 2853 /pm 28 K.

This research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract from the National Aeronautics and Space Administration. Data were obtained using the NASA PTI, which is supported by NASA contracts to JPL.

The author(s) of this abstract have provided an email address for comments about the abstract: thompson@s383.jpl.nasa.gov

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