Alain Jorissen , Pierre-Francois Coheur , Rodrigo Alvarez , & Martin Groenewegen
Institut d'astronomie et d'astrophysique, Université Libre de Bruxelles C.P. 226, Boulevard du Triomphe, B-1050 Bruxelles, Belgium
Mass loss rates along the red giant branch (RGB) and along the asymptotic giant branch (AGB) are a key ingredient for a proper understanding of these evolutionary phases of low- and intermediate-mass stars.
This paper presents preliminary results from an ISO observing program aiming at deriving the mass loss rates of AGB and RGB stars of different luminosities in the galactic globular cluster 47 Tuc. A search for dust-enshrouded AGB stars has also been performed. The cluster 47 Tuc is especially well suited for this study, because (i) it is the closest stellar cluster whose AGB and RGB are well populated, and (ii) previous studies have assigned giants to either the RGB or AGB.
Raster maps of 5 fields covering areas of about
at different distances from the center of the 47 Tuc cluster
have been obtained with ISOCAM at 11.5 
(LW10).
After careful deglitching, transient correction and flat-fielding, a
sensitivity threshold of 
1 mJy is achieved, allowing to detect
giant stars at 11.5
all the way down to the horizontal branch.
Color indices combining ISO and DENIS data are derived in order to investigate the amount of dust emission (and hence mass loss rate) as a function of luminosity along the RGB and AGB. A few obscured sources have been found, and their frequency with respect to the AGB stars at different distances from the cluster center is derived.