Spectral analysis and orbital evolution of Low Mass X-ray Binaries at high inclination

X-Ray binaries are gravitationally bound systems consisting of a compact object that accretes matter from a companion star; they are the most interesting objects of the sky, infact they allow to study the physics of matter in very extreme conditions of density, temperature or magnetic eld. So the determination of spectral and temporal properties of X-ray binaries plays an important role in understanding the processes involved in these systems. This project aims to understand the properties of binary systems, at high inclination (dipping and eclips- ing sources), containing neutron stars weakly magnetized. In the light curves of these systems it is possible to identify a variety of modulations with orbital periodicity that are caused by the high inclination of the orbital plane with respect to the line of sight. Using data from several X-ray satellites such as Chandra, XMMNewton and Suzaku, we analized the spectral properties of the source X1822-371 and temporal evolution of the source XB1916-053. A short introduction about X-ray binary systems and basics about accretion is presented in chapter 1, while in chapter 2 I describe brie y the formation and evolution of binary systems. The results we obtained analizing the source X1822-371 are described in chapter 3. Our aim was to understand the nature of the residuals between 0.6 and 0.8 keV previously observed in the XMM/EPIC-pn data by Iaria et al. (2013). We interpreted the Gaussian feature in absorption as a cyclotron resonant scattering feature (CRSF) produced close to the neutron star surface and derive the magnetic eld strength at the surface of the neutron star. If our interpretation is correct this is the very rst detection of a CRSF below 1 keV in a LMXB. In the source XB 1916-053 the known orbital period derivative is extremely large and can be explained by invoking an extreme, non-conservative mass transfer rate that is not easily justiable. The results of our analysis of a large sample of data are presented in chapter 4. We had found that both in a conservative and non-conservative mass transfer scenario we have to invoke the presence of a third body to explain the observed sinusoidal modulation. We proposed that XB 1916-053 forms a hierarchical triple system.