2005A&A...436..417W

The variability of optical FeII blends in NGC 4051 is examined from spectra extracted from the AGN Watch program. In our analysis, the FeII complex are subtracted and measured, with the following results. Firstly, the FeII variations were detected in NGC 4051 during a 3-year period. The identified FeII variations followed the variations in continuum closely. Secondly, the EW of FeII is reported to increase with rising continuum flux, which is consistent with previous claims that there is no convincing Baldwin Effect in optical FeII. Thirdly, by comparing the variations of Hβ and FeII, we find that R_Fe scales with continuum flux as R_Fe∝(5.0±0.8)log(L/M), which is significantly different from the theoretical expectations. Finally, in six selected Seyferts, four out of five Narrow-Line Seyfert 1 galaxies present positive correlation between R_Fe and the continuum flux. The negative correlations are identified in the remaining two objects that have relatively broad profiles of Hβ (FWHM>1500km/s). We argue that the difference of electron density of broad line clouds and/or variability behavior of incident high-energy radiation can explain the dichotomy in variability behavior of R_Fe.