The formation of Be stars through close binary evolution

Abstract

A simplified model of cas B close binary evolution is presented, on the basis of which the expected fractions of evolved close binaries among intermediate-mass main sequence stars are calculated. During mass transfer, the original secondaries are rejuvenated and spun up. These rapidly rotating B stars should have either a helium star, a white dwarf or a neutron star companion. The effect of uncertainties in the theory of close binary evolution and in the input distributions on the expected fractions are studied. It is found that the amount of mass lost during the mass transfer phase and, to a lesser extent, the distribution of initial transfer phase and, to a lesser extent, the distribution of initial mass ratios, strongly affect the resulting fractions