High mass X-ray binaries in the MilkyWay and beyond: a multiwavelength temporal and spectroscopic study

High Mass X-ray Binaries (HMXBs) represent an important stage in the evolution of massive stars and are some of the brightest sources in the X-ray sky. In the first half of this thesis a detailed analysis of X-ray observations of two HMXBs, the Be/X-ray Binary (BeXRB) Swift J045106.8-694803 and the supergiant/X-ray Binary XTE J0421+560/CI Camelopardalis, is presented. Simulations of the X-ray spectrum of Swift J045106.8-694803 show that both the spectral and timing properties can be reproduced by a blackbody and power law pulsating ∼ pi out of phase with each other. The pulse profile of the blackbody is used to determine the angle between the rotation and magnetic axes of the neutron star and the angle between the rotation axis and line of sight. The apparently broad iron line of XTE J0421+560 is decomposed into three intrinsically narrow lines, FeI-Ka, FeIK b and FeXXIV-XXVKa. The light curve extracted in the energy range defined as the Fe-Ka line from the spectral fits shows marginal evidence for a lag when cross correlated with that of the continuum. The lag is interpreted as the light crossing time of the circumbinary torus and implies a radius of 10 AU. The second part of this thesis considers HMXBs as a population. I describe the search for XRBs in the Phoenix dwarf galaxy, a Local Group dwarf irregular galaxy which share many similarities with the Small Magellanic Cloud (SMC), which has an apparent overabundance of HMXBs. Finally, I discuss why the BeXRB population in the SMC is ideal for population studies and outline the work done to search for evidence for two different neutron star formation channels in their physical parameters