Lognormal variability in BL Lacertae

X-ray data from the blazar BL Lac are used to investigate the nature of its variability, and more precisely the flux dependency of the variability and the distribution of fluxes. The variations in the flux are found to have a lognormal distribution and the average amplitude of variability is proportional to the flux level. BL Lac is the first blazar in which lognormal X-ray variability is clearly detected. Lognormal variability in X-ray light curves, probably related to accretion disk activity, has been discovered in various compact systems, such as Seyfert galaxies and X-ray binaries. The light curve is orders of magnitude less variable than other blazars, with few bursting episodes. If this defines a specific state of the source, then the lognormality might be the imprint of the accretion disk on the jet, linking for the first time accretion and jet properties in a blazar.

[1]  University of Leicester,et al.  On characterizing the variability properties of X-ray light curves from active galaxies , 2003 .

[2]  G. Bicknell,et al.  The Evolution of Shocks in Blazar Jets , 2002, Publications of the Astronomical Society of Australia.

[3]  Y. Lyubarskii,et al.  Flicker noise in accretion discs , 1997 .

[4]  William W. Zhang,et al.  In-orbit performance and calibration of the Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) , 1996, Optics & Photonics.

[5]  Paul S. Smith,et al.  The inner jet of an active galactic nucleus as revealed by a radio-to-γ-ray outburst , 2008, Nature.

[6]  日野 寛三,et al.  対数正規分布(Lognormal Distribution)のあてはめについて , 1994 .

[7]  Ian M. McHardy,et al.  The flux-dependent amplitude of broadband noise variability in X-ray binaries and active galaxies , 2001 .

[8]  Martin J. Rees,et al.  Comptonization of Diffuse Ambient Radiation by a Relativistic Jet: The Source of Gamma Rays from Blazars? , 1994 .

[9]  University of Leicester,et al.  Non‐linear X‐ray variability in X‐ray binaries and active galaxies , 2005 .

[10]  G. Ghisellini,et al.  A jet model for the gamma-ray emitting blazar 3C 279 , 1992 .

[11]  J. Poutanen,et al.  Radiation from relativistic jets in blazars and the efficient dissipation of their bulk energy via photon breeding , 2007, 0709.3043.

[12]  C. Gaskell,et al.  Lognormal X-Ray Flux Variations in an Extreme Narrow-Line Seyfert 1 Galaxy , 2004 .