Variability of optical Fe II complex in narrow-line Seyfert 1 galaxy NGC 4051

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China e-mail: wjy@bao.ac.cn
² National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
³ Department of Astronomy, Beijing Normal University, Beijing 100875, China e-mail: xthe@bun.edu.cn

Received: 15 September 2004
Accepted: 24 January 2005

Abstract

The variability of optical blends in NGC 4051 is examined from spectra extracted from the AGN Watch program. In our analysis, the complex are subtracted and measured, with the following results. Firstly, the variations were detected in NGC 4051 during a 3-year period. The identified variations followed the variations in continuum closely. Secondly, the EW of is reported to increase with rising continuum flux, which is consistent with previous claims that there is no convincing Baldwin Effect in optical . Thirdly, by comparing the variations of Hβ and , we find that  scales with continuum flux as , 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 and the continuum flux. The negative correlations are identified in the remaining two objects that have relatively broad profiles of Hβ (). 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 .