Sensitivity of the Blue Loops of Intermediate-Mass Stars to Nuclear Reactions

TL;DR

This paper examines how changes in the $^{14}$N(p,{\gamma})$^{15}$O reaction rate influence the blue loops in intermediate-mass stars and demonstrates that envelope overshooting can restore these loops to match observations.

Contribution

It reveals the sensitivity of stellar blue loops to nuclear reaction rates and shows that envelope overshooting can counteract the effects of rate modifications.

Findings

Blue loops are severely affected by the $^{14}$N(p,{\gamma})$^{15}$O reaction rate changes.

Envelope overshooting can restore blue loops altered by reaction rate modifications.

The study links nuclear reaction rates to observable stellar features like Cepheid variables.

Abstract

We investigate the effects of a modification of the $^{14}$N(p,{\gamma})$^{15}$O reaction rate, as suggested by recent evaluations, on the formation and extension of the blue loops encountered during the evolution of the stars in the mass range 5M$_{\odot}$ to 12M$_{\odot}$. We show that the blue loops of stars in the mass range 5M$_{\odot}$ to 8M$_{\odot}$, that is the range of super ABG stars, are severely affected by a modification of the important $^{14}$N(p,{\gamma})$^{15}$O reaction rate. We also show that the blue loops can be restored if envelope overshooting is included, which is necessary to explain the observations of the Cepheid stars.