BEXCO - Room F(201/202/203/204)
[GA220] The VHE gamma-ray flare of BL Lacertae in June 2015
BL Lacertae is a blazar at the redshift of z = 0.069, eponym of the BL Lac blazar type. It is also a prototype of the low-frequency-peaked BL Lac (LBL) subclass, and the source was discovered with MAGIC in gamma rays already in 2005. In 2015 MAGIC observations of BL Lacertae were triggered by the Fermi-LAT analysis report in the MAGIC group, and were performed during 10 individual nights between 15th and 28th June for a total of 8.6 h. The measured gamma-ray flux varied between 40% and 10% of the Crab nebula flux above 200 GeV in the nights 15th and 17th June, respectively. In particular, the fast variability was found in the night of 15th June with (33+/-9) minutes of the doubling decay time, statistical errors only. We also performed the multi-wave-length (MWL) observations in the radio, optical, UV, X ray and gamma-ray bands, and the MWL light curves indicate that the very high energy gamma-ray flare was the so-called orphan flare, i.e. no simultaneous activity in other wavebands could be found. In the talk we will present the results of the campaign and discuss their implications on the understanding of the object.