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MAGIC detects an increased activity from BL Lacertae at very high energy gamma-rays

ATel #7660; Razmik Mirzoyan (Max-Planck-Institute for Physics) on behalf of the MAGIC collaboration
on 18 Jun 2015; 19:02 UT
Credential Certification: Razmik Mirzoyan (Razmik.Mirzoyan@mpp.mpg.de)

Subjects: Gamma Ray, TeV, VHE, AGN, Blazar

Referred to by ATel #: 7687

The MAGIC telescopes have detected an increase in the Very High Energy (VHE; >100 GeV) gamma-ray flux from BL Lacertae (RA=22h02m43.3s Dec=+42d16m40s, J2000.0). The preliminary analysis of the MAGIC data taken from 2015/06/14 to 2015/06/17 indicates a highly significant signal above 200 GeV. The emission is variable, with a flux of 0.4 and 0.1 times the flux of the Crab nebula above 200 GeV in the nights 14/15 and 16/17, respectively. MAGIC telescopes observed BL Lacertae in 3 consecutive nights for duration of 1 hour per night, under excellent weather conditions. In the night of 15/16 June there was no detection. The flux level is similar to the flaring state reported in Arlen et al. 2013. In the low state the source is typically not detectable with IACTs. The MAGIC observations were triggered by the high activity measured at optical and gamma-ray energies. The source is active in the high energy gamma-ray band as seen by Fermi-LAT (http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc/source/BL_Lac), and in optical band as reported by Tuorla blazar monitoring program (http://users.utu.fi/kani/1m/BL_Lac.html). We have also triggered ToO observations with the Swift satellite, which did not show any substantial enhancement in the X-ray flux (http://www.swift.psu.edu/monitoring/source.php?source=BLLacertae). MAGIC observations on BL Lacertae will continue during the following nights, and multiwavelength observations are encouraged. The MAGIC contact persons for these observations are R. Mirzoyan (Razmik.Mirzoyan@mpp.mpg.de) and D. Dominis Prester (dijana@phy.uniri.hr). MAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located at the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV.