  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.
