MAIN-SEQUENCE MASSES AND RADII FROM GRAVITATIONAL REDSHIFTS

Modern instrumentation makes it possible to measure the mass-to-radius ratio for main-sequence stars in open clusters from gravitational red shifts. For stars where independent information is available for eithe r the mass or the radius, this application of general relativity direc tly determines the other quantity. Applicable examples are (1) measuri ng the radii of solar metallicity main-sequence stars for which the ma ss-luminosity relation is well known, (2) measuring the radii for star s where model atmospheres can be used to determine the surface gravity (ratio of the mass to the radius squared), (3) refining the mass-radi us relation for main sequence stars, and (4) measuring the change in r adius as stars evolve off the main sequence and up the giant branch.