A phenomenological analysis of the spectral bimodality in the QPO object GX 5-1☆

Abstract Some corrections and inprovements to the beat frequency model for the quasi-periodic oscillation phenomemon in X-ray binaries are made in this paper. The main point is that viscous damping in the column accretion process has been included in the consideration and this has led to a successful explanation of the two-branch spectrum, unaccounted for by the previous beat frequency model.