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Fast optical brightening of BL Lacertae

ATel #3371; V. M. Larionov, E. G.Larionova and N. V.Efimova (Astronomical Institute, St.-Petersburg State University, Russia, and Pulkovo Observatory, Russia), M. Villata and C. M. Raiteri (INAF, Osservatorio Astronomico di Torino, Italy), for the GASP Collaboration
on 23 May 2011; 08:50 UT
Credential Certification: Claudia M. Raiteri (raiteri@oato.inaf.it)

Subjects: Optical, AGN, Blazar

Referred to by ATel #: 3375, 3377, 3380, 3459, 4155, 4271

With reference to ATel #3368, announcing the Fermi LAT detection of increasing gamma-ray activity of BL Lacertae, we report on its optical brightening. Observations in St. Petersburg reveal R = 13.87 +/- 0.01 on May 14.99, R = 13.06 +/- 0.01 on May 21.95 and R = 12.71 +/- 0.01 on May 22.97, with a brightness increase of 0.36 mag in 24.5 hours. These brightness levels are comparable to those reached during the outbursts of 1997-2004.