Obtained fundamental cyclotron energies shown against the 3–50 keV luminosity. The open symbols represent the fundamental energy of the double absorption features, and the filled symbols the energy of the single CRSF. All the date‐sorted data from the brightening (circles) and dimming (triangles) are presented, together with the intensity‐sorted (squares) results. The Ginga results (Paper I) are also included (stars).