Rb-rich asymptotic giant branch stars in the magellanic clouds

Abstract

We present high-resolution (R ∼ 60,000) optical spectra of a carefully selected sample of heavily obscured and presumably massive O-rich asymptotic giant branch (AGB) stars in the Magellanic Clouds. We report the discovery of strong Rb I lines at 7800 in four Rb-rich LMC stars at luminosities equal to or greater than the standard adopted luminosity limit for AGB stars (M bol ∼ -7.1), confirming that "hot bottom burning" may produce a flux excess in the more massive AGB stars. In the SMC sample, just one of the five stars with M bol