Long-term variability of the optical spectra of NGC 4151

Abstract

Aims. We present the results of a long-term monitoring (11 years, between 1996 and 2006) of Hα and Hβ line variations of the active galactic nucleus of NGC 4151. Methods. High quality spectra (S /N > 50 and R ≈ 8 Å) of Hα and Hβ were investigated. During monitoring period, we analyzed line profile variations. Comparing the line profiles of Hα and Hβ, we studied different details (bumps, absorbtion features) in the line profiles. The variations in the different Hα and Hβ line profile segments were investigated. We also analyzed the Balmer decrement for entire lines and for line segments. Results. We found that the line profiles varied strongly during the monitoring period, and exhibited blue and red asymmetries. This is indicative of a complex BLR geometry inside NGC 4151 with, at least, three kinematically distinct regions: one that contributes to the blue line wing, one to the line core and one to the red line wing. The variation may be caused by an accelerating outflow originating very close to the black hole, where the red part may come from a region closer to the black hole than the blue part, which originates in the region with the highest outflow velocities. Conclusions. Taking into account that the BLR of NGC 4151 has a complex geometry (probably affected by an outflow) and that a portion of the broad line emission does not seem to be produced entirely by photoionization, one may ask whether the study of the BLR using reverberation mapping would be worthwhile for this galaxy.

Long-Term Monitoring of the Broad-Line Region Properties in a Selected Sample of AGN

“…0.42 0.05 ± 0.03 1.6 × 10 8 Shapovalova et al, 2008Shapovalova et al, , 2010bRakić et al, 2017Rakić et al, (1996Rakić et al, -2006 6,110 Shapovalova et al, 2001Shapovalova et al, , 2010aJovanović et al, 2010;Popović et al, 2011Popović et al, (1995Popović et al, -2007 11,900 Shapovalova et al, 2016;Kovačević et al, 2017Kovačević et al, (1990Kovačević et al, -2014 5,610…”

The origin of the broad line region in active galactic nuclei

“…First, the observational arguments for both inflow and outflow in BLR were given in a number of papers (e.g. Done & Krolik 1996;Elvis 2000;Ferland et al 2009;Gaskell 2009;Shapovalova et al 2010). Second, there has been considerable discussion of the heating efficiency of the LIL BLR: radiative heating seems too low compared with the observed radiation field, and additional mechanical heating seems to be required (Collin-Souffrin et al 1988;Bottorff & Ferland 2002;Shapovalova et al 2004;Shapovalova et al 2010).…”

Oscillatory patterns in the light curves of five long-term monitored type 1 active galactic nuclei

“…Due to complexity of this object, it might be useful to search for periodicity information hidden in the other wavebands, i. e. the continuum 1370 Å, Lyα and CIV lines collected by IUE satellite from 1978-1992(Wamsteker et al 1997) and from 1994December to 1996March (O' Brien et al 1998 (iv) For NGC 4151, Fig. 3, the light curves include observations from Kaspi et al (1996Kaspi et al ( , covering period over two months in 1993, from Shapovalova et al (2010bShapovalova et al ( , covering period 1996Shapovalova et al ( -2006, and finally we added two observations presented in Bon et al (2012Bon et al ( , one from 1986Bon et al ( , and other from 1989; (v) Up to now, for E1821+643 the only information available are fluxes obtained from its the first long term monitoring campaign conducted by Shapovalova et al (2016) …”