Mass loss and the H-R diagram of globular clusters

Emission wings indicative of mass loss are not in evidence in high resolution observations of H-alpha in fainter stars of the globular clusters M5 and M71. Together with previous determinations of the position in the H-R diagram of globular cluster giants that are undergoing mass loss, these new data establish that the H-R domain of Population II stars showing no optical evidence of mass loss is similar to that of Population I stars. The fact that many stars within this domain show no such evidence, however, suggests that quiescent mass loss may be too sporadic to account for most of the mass loss prior to the horizontal-branch phase. The randomness of the process further suggests that it may be responsible for both the spread in mass on the horizontal branch and the anomalies in the ratio of blue to red horizontal branch stars in clusters of moderate metallicity.