Two-photon emission in X-ray pulsars. I - Basic formulas. II - Radiation transfer

It is suggested that the following processes may determine the spectra of X-ray pulsars such as Her X-1. (1) Nonradiative collisional excitation of electrons to their first Landau level, followed by radiative decay, is the only important source of photons. (2) These cyclotron photons are transferred through the source by being absorbed and re-emitted. (3) Non-cyclotron photons below the cyclotron frequency can be produced by the re-emission process. (4) Non-cyclotron photons above the cyclotron frequency can be produced by a related process. Specific formulas describing the two-photon emission process are derived and expressed in the form of an averaged emission probability. Compound probabilities are defined for absorption plus re-emission and for non-radiative collisional excitation plus cyclotron emission. Interpolation formulas relate these compound probabilities to the probabilities for resonant scattering and resonant bremsstrahlung respectively.