  Extreme objects such as X-ray binaries, AGN, or $\gamma$-ray bursters harbor
high energy plasmas whose properties are not well understood yet. Not only are
they responsible of the hard X- and $\gamma$-ray emission we observe but also
they have a strong influence on the main dynamics and energetics of these
objects themselves. Here we present a new kinetic code that solves the
evolution equations for particles and photons around compact objects. It
produces spectra that will be compared with observations from Simbol-X to
constrain the radiation and acceleration processes in these objects.

Astrophysics