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Optical activity of BL Lacertae

ATel #4031; V. Larionov, D. Blinov, T. Konstantinova (St. Petersburg Univ.)
on 11 Apr 2012; 12:30 UT
Credential Certification: V. Larionov (vlar@astro.spbu.ru)

Subjects: Optical, AGN, Blazar, Quasar

Referred to by ATel #: 4155, 4349, 4557, 4565, 4973

We perform optical photometric and R-band polarimetric monitoring of BL Lac using 70-cm AZT-8 (CrAO, Ukraine) and 0.4-m LX-200 (St.Petersburg, Russia) telescopes, as a part of GASP project. As reported in Atel#4028, this blazar was found by Fermi LAT in active state on 2012 April 9. Our data show that a sharp optical maximum was reached on the date 2012-04-08UT02:20, R=13.10, while on 2012-04-11UT01:30 R=13.40. Optical maximum occurring one day before gamma-ray one suggest negative time lag between two energy ranges. However, this conclusion may be spurious due to the lack of dense optical coverage. Our preliminary light curve may be seen at http://www.astro.spbu.ru/staff/vlar/plots_optical/BLLACr.png . Current high activity state of BL Lac deserves close attention in all wavelengths.