Paper detail

Fundamental properties of High-Mass X-ray Binaries

The aim of this PhD Thesis is to characterize a representative sample of Supergiant X-ray Binaries (SGXBs) formed by 4 sources: XTE J1855-026, a classical SGXB with long-term stable X-ray flux; AX J1841.0-0535 and AX J1845.0-0433, two supergiant fast X-ray transients (SFXTs) with the X-ray emission mostly dominated by flaring; and IGR J00370+6122, something in between these 2 sub-groups. The physical processes that produce these observable differences are still a matter of debate. In this PhD Thesis I performed a study of these 4 different systems to provide new data to constrain the models. This study consists of:(i) the determination of the orbital solution,(ii) a systematic study of the wind behavior along the orbit by the measure of Halpha variations,(iii) a model of stellar atmospheres of the donor star,(iv) establish whether there are X-ray flux variations modulated by the orbital period. The study of the wind shows that Halpha variations are dominated by intrinsic wind processes. The stellar atmospheres study shows that the supergiant stars that harbor these binaries have a higher projected rotational velocity, higher He abundance and higher N/C ratio than that of isolated supergiant stars. The results of this study show that the eccentricity of the binary does not have a simple correlation with the differences in the X-ray flux of the different sub-groups. Therefore, the idea of a more complex scenario is consolidated. The discovery of a new type of system, IGR J00370+6122, which properties do not fit in any of the established sub-groups, reinforces the idea of a continuum in the observed properties more than a strict classification of systems. Furthermore, I have developed a pipeline to reduce spectra of the FRODOSpec spectrograph at the Liverpool Telescope optimized for the reduction of the red spectra of the obscured supergiants that we find in these SGXBs.