Equilibrium Models of Stars Composed of Pure Helium

Abstract

Nine equilibrium models of pure helium stars have been calculated for a range of 1 to 17 solar masses. It is shown that for stars larger than two solar masses radiation pressure cannot be neglected. The main effects are a marked reduction in luminosity and a larger core. The change in luminosity does not alter the "main sequence" line in the Hertzsprung·Russell diagram, but shifts the masses down along this line. There is a small decrease in radius accompanied by a corresponding increase in central density.