# Compulsory Deep Mixing of 3He and CNO Isotopes in the Envelopes of low-mass Red Giants - Astrophysics

Compulsory Deep Mixing of 3He and CNO Isotopes in the Envelopes of low-mass Red Giants - Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: Three-dimensional stellar modeling has enabled us to identify a deep-mixingmechanism that must operate in all low mass giants. This mixing process is notoptional, and is driven by a molecular weight inversion created by the3He3He,2p4He reaction. In this paper we characterize the behavior of thismixing, and study its impact on the envelope abundances. It not only eliminatesthe problem of 3He overproduction, reconciling stellar and big bangnucleosynthesis with observations, but solves the discrepancy between observedand calculated CNO isotope ratios in low mass giants, a problem of more than 3decades- standing. This mixing mechanism, which we call `$\delta\mu$-mixing-,operates rapidly relative to the nuclear timescale of overall evolution, ~10^8 yrs once the hydrogen burning shell approaches the material homogenizedby the surface convection zone. In agreement with observations, Pop I starsbetween 0.8 and 2.0$\Msun$ develop 12C-13C ratios of 14.5 +- 1.5, while Pop IIstars process the carbon to ratios of 4.0 +- 0.5. In stars less than1.25$\Msun$, this mechanism also destroys 90% to 95% of the 3He produced on themain sequence.

Autor: Peter P. Eggleton, David S. P. Dearborn, John C. Lattanzio

Fuente: https://arxiv.org/