ZERO-AGE MAIN-SEQUENCE RADII AND LUMINOSITIES AS ANALYTIC-FUNCTIONS OF MASS AND METALLICITY

We present fitting formulae for the zero-age main-sequence radii and l uminosities of stars as functions of their masses and metallicities. T he formulae cover masses from 0.1 to 100 M circle dot and metallicitie s from Z = 0.0001 to 0.03. Within this range the functions are everywh ere strictly analytic. They take the form of rational functions in mas s with only positive coefficients calculated as polynomials in metalli city. Errors are generally less than 7.5 per cent for luminosity and l ess than 5 per cent for radius. For a solar metallicity of Z = 0.02 th ese errors are less than 3 per cent for luminosity and 1.2 per cent fo r radius.