Astronomy and Astrophysics – Astrophysics
Scientific paper
1997-11-30
Astronomy and Astrophysics
Astrophysics
28 pages LaTeX; 9 postscript figures; accepted for publication in ApJ; e-mail to kawaguti@kusastro.kyoto-u.ac.jp
Scientific paper
10.1086/306105
Aperiodic optical variability is a common property of Active Galactic Nuclei (AGNs), though its physical origin is still open to question. To study the origin of the optical -- ultraviolet variability in AGN, we compare light curves of two models to observations of quasar 0957+561 in terms of a structure function analysis. In the starburst (SB) model, random superposition of supernovae in the nuclear starburst region produce aperiodic luminosity variations, while in the disk-instability (DI) model, variability is caused by instabilities in the accretion disk around a supermassive black hole. We calculate fluctuating light curves and structure functions, $V(\tau)$, by simple Monte-Carlo simulations on the basis of the two models. Each resultant $V(\tau)$ possesses a power-law portion, $[V(\tau)]^{1/2} \propto \tau^{\beta}$, at short time lags ($\tau$). The two models can be distinguished by the logarithmic slope, $\beta$; $\beta \sim$ 0.74--0.90 in the SB model and $\beta \sim$ 0.41--0.49 in the DI model, while the observed light curves exhibit $\beta \sim$ 0.35. Therefore, we conclude that the DI model is favored over the SB model to explain the slopes of the observational structure function, in the case of 0957+561, though this object is a radio-loud object and thus not really a fair test for the SB model. In addition, we examine the time-asymmetry of the light curves by calculating $V(\tau)$ separately for brightening and decaying phases. The two models exhibit opposite trends of time-asymmetry to some extent, although the present observation is not long enough to test this prediction.
Kawaguchi Toshihiro
Mineshige Shin
Turner Edwin L.
Umemura Masayuki
No associations
LandOfFree
Optical Variability in Active Galactic Nuclei: Starbursts or Disk Instabilities? does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Optical Variability in Active Galactic Nuclei: Starbursts or Disk Instabilities?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical Variability in Active Galactic Nuclei: Starbursts or Disk Instabilities? will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-258196