The ultraluminous X-ray source NGC 1313 X-2 - Its optical counterpart and environment F. Grisé, M. W. Pakull, R. Soria, C. Motch, I. A. Smith, S. D. Ryder and M. Böttcher A&A, 486 1 (2008) 151-163 Published online: 27 May 2008 DOI: 10.1051/0004-6361:200809557