Volume 531, July 2011
|Number of page(s)||10|
|Published online||27 June 2011|
Long-term optical variability of PKS 2155-304
Institute for Experimental Physics, Univ. of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
2 School of Physics, Univ. of New South Wales, NSW 2052, Australia
3 Institute for Experimental Physics, Univ. of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
Received: 12 October 2010
Accepted: 9 May 2011
Aims. The optical variability of the blazar PKS 2155-304 is investigated to characterise the red noise behaviour at largely different time scales from 20 days to 10 yrs).
Methods. The long-term optical light curve of PKS 2155-304 is assembled from archival data as well as from so-far unpublished observations mostly carried out with the ROTSE-III and the ASAS robotic telescopes. A forward folding technique is used to determine the best-fit parameters for a model of a power law with a break in the power spectral density function (PSD). The best-fit parameters are estimated using a maximum-likelihood method with simulated light curves in conjunction with the Lomb-Scargle periodogram and the first-order structure function (SF). In addition, a new approach based upon the so-called multiple fragments variance function (MFVF) is introduced and compared to the other methods. Simulated light curves have been used to confirm the reliability of these methods as well as to estimate the uncertainties of the best-fit parameters.
Results. The light curve is consistent with the assumed broken power-law PSD. All three methods agree within the estimated uncertainties with the MFVF providing the most accurate results. The red-noise behaviour of the PSD in frequency f follows a power law with f − β, and a break towards f0 at frequencies lower than .
Key words: BL Lacertae objects: individual: PKS 2155-304 / methods: statistical / galaxies: photometry / accretion, accretion disks / galaxies: jets / black hole physics
© ESO, 2011
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.