Radii and Effective Temperatures for G, K, and M Giants and Supergiants

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Abstract
Interferometrically determined angular diameters obtained at the Palomar Testbed Interferometer (PTI) for 69 giant and supergiant stars are presented. Spectral types of the 59 giant stars generally lie between G6 and M6, although a B7 giant is included; the nine bright giants and supergiants have spectral types between F5 and M5. Comparison of the results to those from the IR Optical Telescope Array interferometer indicate no statistically significant difference between the two data sets. The use of Hipparcos parallaxes allows us to measure linear sizes directly for these stars, which range in size from 10 to 260 solar radii. In conjunction with previous results as reported by Dyck et al., the total of 113 giant stars provides empirically determined dependencies of effective temperature and linear radius upon spectral type and V-K color.