2 5 Fe b 20 09 The ULX NGC 1313 X - 2 : an optical study revealing an interesting behavior

We present a summary of our ongoing efforts to study one of the brightest ultraluminous X-ray source, NGC 1313 X-2. Despite a large coverage in the X-rays, much of the information we have about the source and its environment comes from optical wavelenghts. Here, we report on the properties of the stellar environment, and the differences in the optical counterpart between our two observing epochs (2003–2004 and 2007–2008). We summarize our ongoing program designed to look for radial velocity variations in the optical spectra and for photometric variability.