Open AccessOptical multiband observations of BL Lacertae during the outburst of 2005
Author(s) -
Hu Shao Ming,
Wu J. H.,
Zhao G.,
Zhou X.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10995.x
Subject(s) - physics , astrophysics , light curve , brightness , amplitude , astronomy , telescope , variation (astronomy) , color index , flare , spectral index , photometry (optics) , wavelength , spectral line , optics , stars
The aim of our observations is to investigate the intranight variability properties and the spectral variability of BL Lacertae. 799 optical multiband observations were intensively made with the Beijing–Arizona–Taiwan–Connecticut (BATC) 60/90 cm Schmidt telescope during the outburst composed of two subsequent flares in 2005. The second flare, whose rising phase lasted at least 44 d, was observed with amplitudes of more than 1.1 mag in three BATC optical bands. In general, on intranight time‐scale the amplitude of variability and the variation rate are larger at the shorter wavelength, and the variation rate is comparable in the rising and decaying phases within each band. A possible time‐lag between the light curves in bands e and m , around 11.6 min, was obtained. Based on the analysis of the colour index variation with the source brightness, the variability of BL Lacertae can be interpreted as having two components: a ‘strongly chromatic’ intranight component and a ‘mildly chromatic’ internight component, which may be the results of both intrinsic physical mechanism and geometric effects.