Stochastic model of optical variability of BL Lacertae

¹ St.-Petersburg State Univ., Universitetsky pr. 28, 198504 St.-Petersburg, Russia e-mail: dmitriy.blinov@gmail.com
² Isaac Newton Institute of Chile, St.-Petersburg Branch, Russia

Received: 10 June 2009
Accepted: 20 June 2009

Abstract

Context. We use optical photometric and polarimetric data of BL Lacertae that cover a period of 22 years to study the variability of the source.

Aims. The long-term observations are employed for establishing parameters of a stochastic model consisting of the radiation from a steady polarized source and a number of variable components with different polarization parameters, proposed by the authors early.

Methods. We infer parameters of the model from the observations using numerical simulations based on a Monte Carlo method, with values of each model parameter selected from a Gaussian distribution. We determine the best set of model parameters by comparing model distributions to the observational ones using the  criterion.

Results. We show that the observed photometric and polarimetric variability can be explained within a model with a steady source of high polarization, ~40%, and with direction of polarization parallel to the parsec scale jet, along with 10±5 sources of variable polarization.