Artículos de revistas
Correlation and time delays of the X-ray and optical emission of the Seyfert Galaxy NGC 3783
Fecha
2009-08-21Registro en:
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY Volume: 397 Issue: 4 Pages: 2004-2014 Published: AUG 21 2009
0035-8711
DOI: 10.1111/j.1365-2966.2009.15110.x
Autor
Arévalo, P.
Churazov, E.
Uttley, P.
Lira Teillery, Paulina
Breedt, E.
McHardy, I. M.
Institución
Resumen
We present simultaneous X-ray and optical B- and V-band light curves of the Seyfert Galaxy
NGC 3783 spanning 2 years. The flux in all bands is highly variable and the fluctuations are
significantly correlated. As shown before by Stirpe et al. the optical bands vary simultaneously,
with a delay of less than 1.5 d but both B and V bands lag the X-ray fluctuations by 3–9 d.
This delay points at optical variability produced by X-ray reprocessing and the value of the
lag places the reprocessor close to the broad-line region. A power spectrum analysis of the
light curve, however, shows that the X-ray variability has a power-law shape bending to a
steeper slope at a time-scale of ∼2.9 d while the variability amplitude in the optical bands
continues to grow towards the longest time-scale covered, ∼300 d. We show that the power
spectra together with the small value of the time delay are inconsistent with a picture where all
the optical variability is produced by X-ray reprocessing, though the small amplitude, rapid
optical fluctuations might be produced in this way. We detect larger variability amplitudes on
long time-scales in the optical bands than in the X-rays. This behaviour adds to similar results
recently obtained for at least three other active galactic nuclei and indicates a separate source
of long-term optical variability, possibly accretion rate or thermal fluctuations, in the optically
emitting accretion disc.