| Issue |
A&A
Volume 510, February 2010
|
|
|---|---|---|
| Article Number | A93 | |
| Number of page(s) | 6 | |
| Section | Extragalactic astronomy | |
| DOI | https://doi.org/10.1051/0004-6361/200913536 | |
| Published online | 17 February 2010 | |
The nature of optical and near-infrared variability of BL Lacertae *
1
Astronomical Institute, St.-Petersburg State University, Russia e-mail: vlar@astro.spbu.ru
2
Isaac Newton Institute of Chile, St.-Petersburg Branch, Russia
3
INAF, Osservatorio Astronomico di Torino, Italy
Received:
23
October
2009
Accepted:
4
December
2009
Context. Since 1997, BL Lacertae has undergone a phase of high optical activity, with the occurrence of several prominent outbursts. Starting in 1999, the Whole Earth Blazar Telescope (WEBT) consortium has organised various multifrequency campaigns on this blazar, collecting tens of thousands of data points. One of the main issues in the analysis of this huge dataset has been the study of colour variability.
Aims. The immense amount of optical and near-infrared data collected during the campaigns enables us to perform a thorough analysis of multiband data, with the aim to understand the flux variability mechanisms.
Methods. We use a new approach for the analysis of these data, focusing on the source spectral evolution.
Results. We show that the overall behaviour of the BL Lacertae light and colour curves can be explained in terms of a changing viewing angle of a moving, discrete emitting region, which causes variable Doppler boosting of the corresponding radiation.
Conclusions. A fractal helical structure is suggested to be at the origin of the different time scales of variability.
Key words: BL Lacertae objects: general / BL Lacertae objects: individual: BL Lacertae / galaxies: jets / quasars: general / galaxies: active
Based on data taken and assembled by the WEBT collaboration and stored in the WEBT archive at the Osservatorio Astronomico di Torino – INAF (http://www.oato.inaf.it/blazars/webt/).
© ESO, 2010
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.