2002ApJ...571..458O

Deep images in the 10 µm spectral region have been obtained for five massive Galactic globular clusters, NGC 104 (=47 Tuc), NGC 362, NGC 5139 (=ω Cen), NGC 6388, NGC 7078 (=M15), and NGC 6715 (=M54) in the Sagittarius Dwarf Spheroidal using the ISOCAM on board the Infrared Space Observatory in 1997. A significant sample of bright giants have an ISOCAM counterpart, but only fewer than 20% of these have a strong mid-IR excess indicative of dusty circumstellar envelopes. From a combined physical and statistical analysis we derive mass-loss rates and frequency. We find that (1) significant mass loss occurs only at the very end of the Red Giant Branch evolutionary stage and is episodic, (2) the modulation timescales must be greater than a few decades and less than a million years, and (3) mass-loss occurrence does not show a crucial dependence on the cluster metallicity.