We thank B. Freytag for valuable discussions on surface convection zones. J.M.W. and A.J.F. thank the Konrad-Zuse-Zentrum für Informationstechnik Berlin and the HLRZ, Jülich for a generous grant of computing time. A.J.F. was supported by the DFG (grant Se 420/8-1) and J.M.W. by the BMBF (grant 05 3BT13A 6).
© European Southern Observatory (ESO) 1998
Online publication: April 20, 1998