Abstract EN:

The study of the high energy emission (>20 keV) is essential for understanding the radiative processes inherent to accretion flows onto compact objects (black holes and neutron stars). The X/gamma-ray continuum of these systems is successfully interpreted in terms of two components. The first component corresponds to blackbody emission from a geometrically thin optically thick accretion disk while the second component is generally associated to Compton scattering of the thermal disk flux off hot electrons. Despite considerable advances throughout the years, the heating mechanisms as well as the structure of the Comptonizing medium remain poorly understood. In order to enhance our understanding of these aspects, we take advantage of the data archive accumulated by the SPI instrument, a high energy spectrometer (20 keV – 8 MeV) developed at the CESR (now IRAP, Toulouse, France) for the INTEGRAL mission. Above 150 keV, SPI combines a unique spectral resolution with unequalled sensitivity, being thus an ideal tool to study the high energy emission of accreting compact objects. This thesis comprises the results of timing and spectral studies of three individual systems. Despite major differences in their main properties (nature of the compact object, stability of the accretion flow etc. ), all three systems show a significant high energy excess with respect to the emission laws that are commonly used to describe their spectra. In the lights of the SPI results, the possible physical origins of the high energy emission of stellar-size compact objects are presented and discussed, showing that all luminous states can be explained by a non-thermal magnetized corona model.