Astrometric and photometric monitoring of GQ Lupi and its sub-stellar companion R. Neuhäuser, M. Mugrauer, A. Seifahrt, T. O. B. Schmidt and N. Vogt A&A, 484 1 (2008) 281-291 Published online: 17 January 2008 DOI: 10.1051/0004-6361:20078493