2001A&A...374..770M


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.26CET02:26:46

2001A&A...374..770M - Astronomy and Astrophysics, volume 374, 770-783 (2001/8-2)

Characteristics of the continuum variability of the nucleus of NGC 4151 in the optical from 1989-1996.

MERKULOVA N.I., METIK L.P. and PRONIK I.I.

Abstract (from CDS):

The Structure Function (SF) analysis of variable fluxes of the Seyfert galaxy NGC 4151 obtained during its extraordinary brightening in 1989-1996 in the UBVRI bands is reported. More than 1500 measurements were made in each spectral band. The logarithmic slopes of SFs for all samples of flux observations are found to be different for intranight and extranight flux variations: 0.81-0.96 and 0.44-0.60, respectively. The dependence of the SF slopes on the phase of nucleus activity was revealed. The SF slopes increased for intranight variations in accordance with the nucleus brightening and decreased for yearly variations. The processes causing the flux variations evolved during the nucleus brightening in different directions: for intranight variations the process evolved from flicker-noise to extreme shot-noise; for yearly variations - vice versa. The obtained data provide evidence in favor of the supposition that intranight and extranight variations are caused by different sources. As a result, the variable source of the NGC 4151 nucleus during the active phase in the UBVRI bands exhibited characteristics of radio loud AGNs. The highest values of logarithmic slopes of SF for variations on a time scale of years were in the range 0.8≤b≤1.1, and for 10-150 day flares they were as high as 2.2. There was flattening of the optical spectrum with increasing nucleus brightness. The brightness amplitude of the nucleus in the U band reduced to an aperture D=5'' over 7.3 years increased by a factor of more than 50. The brightness in the U band varied by a factor of more than 10 per year. The obtained characteristics of the variable source acting in the NGC 4151 nucleus from 1990-1996 do not contradict the model where the increasing nucleus brightening is caused by clouds of synchrotron radiation ejected from the nucleus during its active period.

Abstract Copyright:

Journal keyword(s): galaxies: individual: NGC 4151 - Seyfert - active nuclei: optical variability

Simbad objects: 9

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Number of rows : 9

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 3C 84 Sy2 03 19 48.1597607660 +41 30 42.114155434   13.10 12.48 11.09   ~ 3616 3
2 Mrk 1095 Sy1 05 16 11.4093760763 -00 08 59.158774578   14.30 13.92     ~ 801 1
3 8C 0716+714 BLL 07 21 53.4484901266 +71 20 36.362058601   15.5 14.17 14.27   ~ 1155 1
4 QSO J0854+2006 BLL 08 54 48.8749311881 +20 06 30.642936668   15.91 15.43 15.56   ~ 2060 1
5 8C 0958+561 QSO 10 01 20.6915852239 +55 53 55.595776916   17.16 16.95     ~ 703 3
6 NGC 3783 Sy1 11 39 01.7095761008 -37 44 19.008597647   12.46 13.43 11.33 12.1 ~ 1500 0
7 NGC 4151 Sy1 12 10 32.5771747733 +39 24 21.057727323   12.18 11.48     ~ 3434 2
8 NGC 5548 Sy1 14 17 59.5401093128 +25 08 12.600227883   14.35 13.73     ~ 2444 0
9 NGC 7469 Sy1 23 03 15.674 +08 52 25.28 12.60 13.00 12.34     ~ 1917 3

    Equat.    Gal    SGal    Ecl

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2021.02.26-02:26:46

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