High Precision, Directly Determined Radii and Effective Temperatures for Giant Stars

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The investigators plan to significantly improve measurements of stellar temperatures and radii using optical interferometry of 425 giant stars, whose distances are accurately determined from a recent reanalysis of the Hipparcos dataset. Through direct measurements of effective temperature, linear radius and limb darkening, models that indirectly predict such values will be calibrated. They will use angular size data from the Palomar Testbed Interferometer (PTI) and Navy Optical Interferometer (NOI) in conjunction with spectrophotometry to directly determine temperature, radius, and stellar structure for the giant stars at unprecedented levels of accuracy. Optical and nearinfrared data will be used to constrain the bolometric fluxes, which in combination with PTI angular diameters will provide direct measures of temperature. This work will have broader impacts to many fields of stellar astrophysics, including structure, modeling, evolution, galactic spectral synthesis, exoplanetary science and planet/star formation theory. They will also participate in a public outreach program with Lowell Observatory.