Project Title: Red Giants in Globular Clusters
Project Advisor: Dr. Andrea Dupree
Background: The color magnitude diagrams of globular clusters are determined
principally by metallicity, but there is an unknown 'second parameter'. Candidates
for the second parameter include age, He abundance, CNO abundance, free-floatingplanets, rotation,
mass loss... and many others. Stellar evolution requires mass loss as
a star ascends the red giant branch, but this has not been observed.
Scientific Questions: Does rotation play a role? Does mass loss play a role? Where does
mass loss occur?
Scientific Methodology: We have Magellan/MIKE echelle spectra of red giants in a number of clusters
to test various proposals for the second parameter. We have
synthesised photospheric spectra. The optimum region for rotation determination
needs to be identified and the rotation of these stars determined.
Additionally, we want to make semi-empirical models of the
chromospheres of these stars to evaluate the mass loss rate quantitatively.