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Session 46 - Variable Stars - Late Type.
Display session, Thursday, January 08
Exhibit Hall,

[46.03] Improved Color-Temperature Relations for Cool Stars

M. L. Houdashelt, R. A. Bell (U. Maryland)

Color-temperature relations are a necessary ingredient in addressing many astrophysical problems. They are especially important when using isochrones to age-date star clusters, since the isochrones must first be transformed from the theoretical (log T_e, log L) to the observational (color, magnitude) plane before they can be compared to stellar photometry. As part of our galaxy population synthesis program, we have calculated the transformation relations required to put the raw synthetic colors -- colors measured from synthetic spectra using commonly-accepted filter transmission profiles -- onto the observed photometric systems. In this poster, we present the color transformations that we have derived from synthetic spectra of a group of F1--K5 stars which have well-determined effective temperatures, surface gravities and metallicities. The effective temperatures of most of these stars were estimated by Bell amp; Gustafsson (1989) using the infrared flux method, and their adopted temperature scale is confirmed in a companion poster (Bell amp; Houdashelt) using the recent angular diameter measurements of Mozurkewich. We demonstrate the necessity and effectiveness of the derived color transformations by applying them to a 4 Gyr, solar-metallicity isochrone and comparing the results to various color-magnitude diagrams of the Galactic open cluster M67. The color-temperature relations which result after the synthetic colors have been transformed to the observational systems are also compared to previous determinations.

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