Part I Physical Processes.- 1 The framework.- 2 Radiation of an accelerated charge.- 3 Bremsstrahlung.- 4 Cyclotron line emission.- 5 Synchrotron emission.- 6 Compton processes.- 7 Comptonisation.- 8 Pair Processes.- 9 Particle acceleration.- 10 Accretion.- 11 Radiation inefficient accretion flows.- Part II Astrophysical Objects.- 12 Black holes and accretion efficiency.- 13 Neutron Stars.- 14 Pulsars.- 15 The Hulse-Taylor pulsar and gravitational radiation.- 16 X-ray binaries.- 17 X-ray binaries evolution.- 18 Relativistic jets.- 19 Gamma ray bursts.- 20 Active galactic nuclei.- 21 The diffuse X-ray background and other cosmic backgrounds.- Index.