AAS 201st Meeting, January, 2003
Session 115. Cool Star Atmospheres and Envelopes
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[115.07] Multi-Epoch Interferometric Study of MIRA Variables II. Narrowband diameters of R Boo

R.R. Thompson (JPL), M.J. Creech-Eakman (JPL / Caltech), G.T. van Belle (Interferometry Science Center / Caltech)

As part of the long-term monitoring of Mira variables at the Palomar Testbed Interferometer, we report high-resolution narrowband angular sizes of the oxygen-rich Mira R Bootis The dataset spans five pulsation cycles for a total of 1496 25-sec observations), and represents the second study to correlate multi-epoch narrowband interferometric data of Mira variables. When the calibrated visibility data are fit using a uniform disk brightness model, differences are seen in their angular diameters as a function of wavelength within the K band (2.0 - 2.4 \mum); the source of which are molecular absorptions in or above the photosphere of the oxygen-rich Mira. Using visible photometric data provided by the AFOEV, the continuum minimum size tracks the visual maximum brightness as found in our previous study (Paper I) for the oxygen-rich Mira S Lac. Based on the mean of the continuum angular diameter cycloid, basic stellar parameters are computed for R Boo, with this star showing maximum atmospheric extension with respect to the 2.0 and 2.4 \mum diameters near phase 0.95. Using the mean value of the fitted cycloids, R Boo has a radius Rmean = 217 ± 40 R\odot and a mean Teff = 2961 ± 43 K .The dominant source of error in the mean radius is the large uncertainty in the distance to this star. Cyclical differences between wideband and narrowband 2.2 \mum angular diameters are explored, and no evidence for departures from circular symmetry were found.

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

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