Which physics determines the location of the mean molecular weight minimum in red giants?

Summary, in English

Stars ascending the red giant branch develop an inversion in mean molecular weight (mu) owing to the burning of He-3 in the region immediately above their hydrogen-burning shells. This inversion may drive thermohaline mixing and thereby be responsible for the extra mixing which is observationally indicated on the red giant branch. In this paper, we investigate the physical influences that determine the mass and temperature at which the inversion in mu develops. We find that it depends most strongly on the thermal structure of the envelope - the profiles of density and temperature in the region of the star immediately above the shell - and is otherwise relatively insensitive to abundances and nuclear reaction rates. The changes in the effects of thermohaline mixing as stars proceed up the giant branch can mostly be understood in terms of their changing thermal structure, driven by their increasing core mass.

• Author: Ross Church; John Lattanzio; George Angelou; Christopher A. Tout; Richard J. Stancliffe
• Department/s: Lund Observatory - Has been reorganised
• Publishing year: 2014
• Language: English
• Pages: 977-984
• Publication/Series: Monthly Notices of the Royal Astronomical Society
• Volume: 443
• Issue: 2
• Links: http://dx.doi.org/10.1093/mnras/stu1195
• Document type: Journal article
• Publisher: Oxford University Press
• Topic: Astronomy, Astrophysics and Cosmology
• Keywords: methods: numerical; stars: abundances; stars: evolution
• Status: Published
• ISBN/ISSN/Other: ISSN: 1365-2966