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G.T. van Belle, R.R. Thompson (Jet Propulsion Laboratory), PTI Collaboration
Using the Palomar Testbed Interferometer (PTI), we have measured angular diameters in the H and K bands for over 50 giant and supergiant stars, ranging in spectral type from A2 to M8. These diameters are part of an ongoing observational program at PTI to empirically establish effective temperatures and linear radii for these stars, in combination with existing photometry and Hipparcos distances for these objects; temperatures range from 3,000K to 7,000K, radii range from 2 to 300 solar radii. The dependence of these two parameters upon spectral type, luminosity class and V-K color is explored for consistency with and departures from expected trends. In contrast to our earlier work (van Belle et al. 1999), three new areas are emphasized: First, 0.1-micron narrowband measurements across the K band are examined in detail. Second, a large subset of the newly observed stars has also been observed interferometrically in the visible, allowing for a comparison of the relative sizes. Third, an emphasis on earlier type objects has resulted in a large number of angular sizes for B, A, F and G spectral types, complimenting our earlier investigation.
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