Age variation of helium abundance in He-rich stars.

Abstract

Investigations of the He abundance variation depending on the age of He-rich stars have been continued. A comparison of the Hipparcos satellite absolute magnitudes and lg g with data obtained previously from the β parameters of multicolour photometry has shown good agreement (Gomez et al., 1998). A critical revision of all previous data, using the Hipparcos data, has confirmed the preliminary conclusion that the helium abundance in the atmospheres of He-rich stars grows with age on average from 0.14 - 0.40 as these stars evolve from the zero-age main sequence across the main sequence within lg g = 4.35 - 3.50. The relationship cuts off at lg g = 3.50 probably having reached a maximum.