2008A&A...486...99S


Query : 2008A&A...486...99S

2008A&A...486...99S - Astronomy and Astrophysics, volume 486, 99-111 (2008/7-4)

Long-term variability of the optical spectra of NGC4151. I. Light curves and flux correlations.

SHAPOVALOVA A.I., POPOVIC L.C., COLLIN S., BURENKOV A.N., CHAVUSHYAN V.H., BOCHKAREV N.G., BENITEZ E., DULTZIN D., KOVACEVIC A., BORISOV N., CARRASCO L., LEON-TAVARES J., MERCADO A., VALDES J.R., VLASYUK V.V. and ZHDANOVA V.E.

Abstract (from CDS):

Result. of long-term spectral monitoring of the active galactic nucleus of NGC4151 are presented (11 years, from 1996 to 2006). High quality spectra (S/N>50 in the continuum near Hα and Hβ) were obtained in the spectral range ∼4000 to 7500Å, with a resolution between 5 and 15Å, using the 6-m and the 1-m SAO's telescopes (Russia), the GHAO's 2.1-m telescope (Cananea, Mexico), and the OAN-SPM's 2.1-m telescope (San-Pedro, Mexico). The observed fluxes of the Hα, Hβ, Hγ, and HeIIλ4686 emission lines and of the continuum at the observed wavelength 5117Å were corrected for the position angle, the seeing, and the aperture effects. We found that the continuum and line fluxes varied strongly (up to a factor 6) during the monitoring period. The emission was maximum in 1996-1998, and there were two minima in 2001 and in 2005. As a consequence, the spectral type of the nucleus changed from a Sy1.5 in the maximum activity state to a Sy1.8 in the minimum state. The Hα, Hγ, and Heλ4686 fluxes correlated well with the Hβ flux. The line profiles were strongly variable, showing changes of the blue and red asymmetry. The flux ratios of the blue/red wings and of the blue (or red) wing/core of Hα and Hβ varied differently. We considered three characteristic periods during which the Hβ and Hα profiles were similar: 1996-1999, 2000-2001, and 2002-2006. The line-to-continuum flux ratios were different; in particular during the first period (1996-1999), the lines were not correlated with the continuum and saturated at high fluxes. In the second and third periods (2000-2006), where the continuum flux was small, the Hα and Hβ fluxes were well correlated to the continuum flux, meaning that the ionizing continuum was a good extrapolation of the optical continuum. The CCFs are often asymmetrical and the time lags between the lines and the continuum are badly defined, indicating the presence of a complex BLR, with dimensions from 1 to 50 light-days. We discuss the different responses of Hβ and Hα to the continuum during the monitoring period.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: individual: NGC4151

VizieR on-line data: <Available at CDS (J/A+A/486/99): table2.dat table3.dat table45.dat table7.dat>

Simbad objects: 3

goto Full paper

goto View the references in ADS

Number of rows : 3
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NGC 4151 Sy1 12 10 32.5759813872 +39 24 21.063527532   12.18 11.48     ~ 3698 2
2 NGC 5548 Sy1 14 17 59.5400291832 +25 08 12.603122268   14.35 13.73     ~ 2716 0
3 ICRF J184208.9+794617 Sy1 18 42 08.9904975672 +79 46 17.127835104   16.06 15.38     ~ 1317 0

To bookmark this query, right click on this link: simbad:objects in 2008A&A...486...99S and select 'bookmark this link' or equivalent in the popup menu