X-ray image of M33 obtained by cumulating all the Swift-XRT observations, with the optical contour levels superimposed, showing the position of M33 X-8 coincident with the optical center of the galaxy. Contour levels are derived from the DSS image³ and have a linear spacing in intensity with a constant ratio of 0.13 beetween consecutive levels and the faintest level corresponding to 10% of the maximum intensity in the image.