The cyclotron emission of anisotropic electrons in the X-ray pulsars
  The spectrum of cyclotron radiation is calculated for anisotropically distributed relativistic electrons with a nonrelativistic velocity scattering across the magnetic field. It is shown that if such electrons are responsible for a formation of the "cyclotron" line in the spectrum of Her X-1, then the value of its magnetic field $(3-6)\cdot 10^{10}$ Gs resulting from this interpretation is in a good agreement with some other observations and theoretical estimations. Observations of a time dependence of the energy of this "cyclotron" line in the spectra of several X-ray pulsars is explained by a variability of the average longitude energy of the electrons, decreasing with increasing liminocity due to radiational braking of the accretion flow. 
A.N.Baushev and G.S.Bisnovatyi-Kogan