Modelling Multiwavelength Emission of Ultra-luminous X-ray sources: theory versus observations

The main goal of my PhD Thesis was to investigate the nature of ULXs using their multiwave-length emission properties and to extend the treatment of the evolution of their binary systems including the effects of super-Eddington accretion. In this way we constrain the masses of the black holes and donor stars in these systems, and their accretion regime. To this end, we developed a code that enables us to constrain the properties of ULXs binaries from their position on the Color-Magnitude Diagram, from their multiwavelength SED and from additional information available on the systems (such as the age of its parent stellar population). A novelty of this present treatment is the inclusion of super-Eddington accretion, with the possibility to produce the output in the HST photometric system; the extension of the parameter space for BH and donor masses with a proper computation of the orbital angular momentum loss during super-critical accretion; the possibility to model the Multiwavelength emission of ULXs considering the effects of a Comptonzing corona covering the innermost regions of the disc.