Evolutionary implications of the new triple-alpha nuclear reaction rate for low mass stars

TL;DR

This study investigates how a new, significantly different triple-alpha nuclear reaction rate affects the evolution of low mass stars, revealing that it shortens or eliminates the red giant phase, conflicting with observations.

Contribution

It introduces the implications of the OKK triple-alpha rate on low mass star evolution, contrasting it with the traditional NACRE rate and highlighting its incompatibility with observations.

Findings

OKK rate shortens or eliminates the red giant phase

Incompatibility of OKK rate with observed red giant branches

Severe impact on late stellar evolution stages

Abstract

Context: Ogata et al. (2009; hereafter OKK) presented a theoretical determination of the triple-alpha nuclear reaction rate. Their rate differs from the NACRE rate by many orders of magnitude at temperatures relevant for low mass stars. Aims: We explore the evolutionary implications of adopting the OKK triple-alpha reaction rate in low mass stars and compare the results with those obtained using the NACRE rate. Methods: The triple-alpha reaction rates are compared by following the evolution of stellar models at 1 and 1.5 Msol with Z=0.0002 and Z=0.02. Results: Results show that the OKK rate has severe consequences for the late stages of stellar evolution in low mass stars. Most notable is the shortening--or disappearance--of the red giant phase. Conclusions: The OKK triple-alpha reaction rate is incompatible with observations of extended red giant branches and He burning stars in old stellar systems.