Multiband studies of Neutron Stars in Low Mass X-ray Binary systems & the HERMES project

The study of the X-ray spectra of accreting compact objects such as neutron stars, and in particular the emission and absorption features common in the X-ray systems, provides a powerful tool to investigate the innermost parts of the accretion disc and the regions close to the compact object. The first part of my work concerned the analysis of the spectra, of two bright, persistent accreting low-mass X-binaries classified as atoll sources: GX 3+1 and GX 9+9. Broad emission features are shown in the spectrum of the first source; on the contrary, the second one shows the total absence of the reflection components and different scenarios have been proposed to explain this unexpected lack. The second part of this work regarded the HERMES satellite: a prototype modular detector for photons in the energy band from 4 keV to 1 MeV. The ensemble of these detectors represents an extraordinary instrument to estimate, using the trilateration method, he position of the Gamma Ray Burst with unprecedented accuracy. A first evaluation of these delays, computed through simulations, will be provided.