VLT optical observations of the isolated neutron star RX J0420.0-5022 R. P. Mignani, C. Motch, F. Haberl, S. Zane, R. Turolla and A. Schwope A&A, 505 2 (2009) 707-713 Published online: 11 August 2009 DOI: 10.1051/0004-6361/200912600