We would like to thank Jean-Paul Zahn for his careful reading of this manuscript. This work was supported by grants from the GDR 131 "Structure Interne des Etoiles et Planètes Geantes" (CNRS). S.T. gratefully acknowledges support from NSERC of Canada and from the French Ministère des Affaires Étrangères.
© European Southern Observatory (ESO) 1998
Online publication: June 26, 1998