We acknowledge J. A. Caballero;
M. R. Zapatero Osorio;
V;
J;
S;
Béjar;
W;
Brandner;
A;
Bayo;
A. Burgasser and B. Burningham for their help;
their corrections and contructive criticism. We thank in particular our referee T. Dupuy for his useful advice;
which substantially helped to improve our paper. This work was supported by Sonderforschungsbereich SFB 881 The Milky Way System (subproject B6) of the German Research Foundation (DFG);