Vibrational Stability of Pure Helium Stars Surrounded by Pure Hydrogen Envelopes

Abstract

This paper investigates the influence of a pure hydrogen envelope on the vibrational stability of pure helium stars and establishes the limiting mass 88 a function of the fractional mass of such an envelope. It is found that an envelope with a mass fraction of the order of 10-4 will make the star vibrationa.lly stable, even when the total mass of the star is well above the limiting mass for pure helium stars.