RGB

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Red Giant Branch stars -- RGB stars (See Wikipedea definition)

3-D stellar evolution modeling revealed a new deep mixing mechanis -- Delta_mu mixing, which is inevitable for low mass stars (< 2 Msun) in their RGB evolutionary phase (before He flash). It is driven by a molecular weight inversion created by the ³He(³He,2p)⁴He reaction above the H-burning shell. This mixing operates fast once the H-burning shell reaches the surface convection zone, which explains how the large amount of 3He (produced by p-p chain) is destroyed before being ejected into interstellar space, as expected from observations. In agreement with observations, Population I stars (0.8~2 Msun) also produce 12C/13C ~ 14.5+-1.5, while Population II stars produce 12C/13C ~ 4.0+-0.5. (from Eggleton et al., 2008ApJ...677..581E)
(Cranmer & Saar, arXiv:1108.4369)
They computed MHD models for mass loss from cool MS stars and RGB stars and give an IDL code to compute the mass loss in a better way. The new mass loss law is found to be better than the classic Reimers law and more recent formula of Schröder & Cuntz (2005).

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