From stars to nuclei

TL;DR

This paper reviews the physical principles of stellar evolution, emphasizing the importance of nuclear reaction rates, and discusses how certain stars like Wolf-Rayet types can provide constraints on these nuclear processes.

Contribution

It highlights the necessity of precise nuclear reaction rate measurements and discusses how specific stellar observations can inform nuclear physics and galactic chemical evolution.

Findings

Wolf-Rayet stars show CNO equilibrium patterns at their surface.

Surface abundance of $^{22}$Ne in WC stars reflects initial CNO content.

Recent measurements support solar metallicity estimates by Asplund et al. (2005).

Abstract

We recall the basic physical principles governing the evolution of stars with some emphasis on the role played by the nuclear reactions. We argue that in general it is not possible from observations of stars to deduce constraints on the nuclear reaction rates. This is the reason why precise measurements of nuclear reaction rates are a necessity in order to make progresses in stellar physics, nucleosynthesis and chemical evolution of galaxies. There are however some stars which provides useful constraint on nuclear processes. The Wolf-Rayet stars of the WN type present at their surface CNO equilibrium patterns. There is also the particular case of the abundance of $^{22}$Ne at the surface of WC stars. The abundance of this element is a measure of the initial CNO content. Very interestingly, recent determinations of its abundance at the surface of WC stars tend to confirm that massive stars in the solar neighborhood have initial metallicities in agreement with the Asplund et al. (2005) solar abundances.