ΔY/ΔZ from fine structure in the main sequence based on Hipparcos parallaxes
Pagel, B. E. J.; Portinari, L.
Denmark, Italy
Abstract
The slope ΔY/ΔZ is a quantity of interest in relation to stellar evolution, the initial mass function and the determination of the primordial helium abundance. In this paper we estimate ΔY/ΔZ from fine structure in the main sequence of nearby stars from Hipparcos data for stars with Z<=Zsolar. We find a value of about 3, which is consistent with what has been found in extragalactic HII regions and with stellar models for suitable upper limits to the initial masses of supernovae according to the initial mass function slope adopted.