Science Colloquium
Nucleosynthesis and Extra Mixing in Low-Mass Red Giants
Dr. Pavel Denisenkov
Dartmouth University
Friday, April 29, 2005
12:25 - 1:20 PM
Hamilton Room 301
The latest observational data on the evolutionary variations of the surface chemical composition in low-mass stars are used to constrain the basic properties of extra mixing in the majority of upper red giant branch (RGB) stars. A possible mechanism of this "canonical" extra mixing is shear turbulence fed by differential rotation. I propose the hypothesis that some of the upper RGB stars may be experiencing "enhanced" extra mixing, which is much faster and somewhat deeper than canonical extra mixing. This could explain the phenomenon of Li-rich giants. Enhanced extra mixing may be triggered by the spinning up of the red giants as a result of their engulfing of Jovian-type planets or due to the tidal synchronization of their spin and orbital rotation in close binary systems.
