Abundances of RGs in Galactic globular clusters

While such a phenomena is not predicted by canonical models of stellar interiors and evolution, it is widely held to be the result of some extra mixing operating during red giant branch ascent which transports material exposed to the CN(O)-cycle across the radiative zone in the stellar interior and into the base of the convective envelope, whereupon it is brought rapidly to the stellar surface.

Here we present measurements of [C/Fe] abundances among 67 red giants in 19 globular clusters within the Milky Way. Building on the work of Martell et al. (2008AJ....136.2522M), we have concentrated on giants with absolute magnitudes of M_V_~-1.5 within clusters encompassing a range of metallicity (-2.4<[Fe/H]<-0.3). The Kitt Peak National Observatory (KPNO) 4 m and Southern Astrophysical Research (SOAR) 4.1 m telescopes were used to obtain spectra covering the {lambda}4300 CH and {lambda}3883 CN bands.