1995A&A...303..405D

We have studied the continuum and emission line variations of NGC 5548 for the entire monitoring campaign as well as for the three individual events of 1989. An ionization stratification of the BLR is indicated by the luminosity weighted radius of the BLR using the centroid of the ICCF and the upper limit of the BLR size provided by the HWZI of the ACF_line given by the entire campaign as well as by each event. The individual events yield a different upper limit of the BLR's extent as a function of the continuum outburst. The relation of the relative change of the emission line flux with respect to the continuum flux delayed by the determined lag have been investigated. The high ionization lines N V λ1240 and HeIIλ1640 seem to follow nearly linear the continuum variations while the other emission lines show signatures of nonlinear response indicated by the least square fits to the F_cont(t) vs. F_line(t+τ) relations. We have measured the integrated emission line and continuum flux for each event. The integrated total line flux of the individual events appear to respond nonlinear to the integrated continuum flux. Further indications for nonlinear response is given by the width of ACF_line in comparison with ACF_cont.