We obtain stringent constraints on the actual efficiency of mass loss for red giant branch stars in the Galactic globular cluster 47 Tuc , by comparing synthetic modeling based on stellar evolution tracks with the observed distribution of stars along the horizontal branch in the colour-magnitude-diagram .
We confirm that the observed , wedge-shaped distribution of the horizontal branch can be reproduced only by accounting for a range of initial He abundances –in agreement with inferences from the analysis of the main sequence– and a red giant branch mass loss with a small dispersion .
We have carefully investigated several possible sources of uncertainty that could affect the results of the horizontal branch modeling , stemming from uncertainties in both stellar model computations and the cluster properties such as heavy element abundances , reddening and age .
We determine a firm lower limit of \sim 0.17 M _ { \odot } for the mass lost by red giant branch stars , corresponding to horizontal branch stellar masses between \sim 0.65 M _ { \odot } and \sim 0.73 M _ { \odot } ( the range driven by the range of initial helium abundances ) .
We also derive that in this cluster the amount of mass lost along the asymptotic giant branch stars is comparable to the mass lost during the previous red giant branch phase .
These results confirm for this cluster the disagreement between colour-magnitude-diagram analyses and inferences from recent studies of the dynamics of the cluster stars , that predict a much less efficient red giant branch mass loss .
A comparison between the results from these two techniques applied to other clusters is required , to gain more insights about the origin of this disagreement .