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R.R. Thompson (JPL/U. Wyoming), M.J. Creech-Eakman (JPL/Caltech), G.T. van Belle (JPL)
We report angular size measurements of 14 oxygen-rich and 4 carbon-rich Mira variables taken at the Palomar Testbed Interferometer (PTI) as part of a long-term observational program. These data represent the first direct measurements, both spatially-resolved (1.5-5.0 mas) and spectrally-resolved, in 0.1 um bins spread over the K-band, as a function of phase. Additionally, diameters taken in 4 spectral channels over the H-band are presented.
Utilizing the AFOEV and AASVO databases to determine the concurrent phase in visual light, periodic changes in the 2.2 um diameter with respect to the band edges (2.0 and 2.4 um) are seen for O-rich Miras. A more uniform angular size structure with respect to wavelength is seen in C-rich Miras. Comparisons are also made to O- and C-rich non-Mira giants which have not been shown to exhibit these characteristics.
This work is part of the Mira observational program at PTI to investigate the effects of chemistry (C/0 ratio, metal abundance), period length, and strength of the pulsational shocks as evidenced in the spectral variability with phase, mainly across the K-band.
The author(s) of this abstract have provided an email address for comments about the abstract: thompson@huey.jpl.nasa.gov