Stellar Evolution. I. The Approach to the Main Sequence.

Abstract

The manner in which nuclear reactions replace gravitational contraction as the source of stellar luminosity is investigated for model stars of population I composition in the mass range 0.5 <M/M0 < 15 0. By following in detail the depletion of C" from high initial values down to values corresponding to equilibrium with N'4 in the C-N cycle, the approach to the main sequence in the Hertzsprung-Russell diagram and the time to reach the main sequence, for stars with M 1.25 M0, are found to differ significantly from data reported previously.