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MAGIC detects an unprecedented activity from the blazar 1ES 1218+304 at very high energy gamma rays

The MAGIC telescopes have observed an unprecedented level of very-high-energy (VHE ; >100 GeV) gamma-ray flux from 1ES 1218+304 (12h21m21.941s, +30d10m37.11s, J2000.0). The preliminary analysis of the data from 2018/12/31 to 2019/01/02 indicates a VHE gamma-ray flux reaching the level of ~25 % of the flux from the Crab nebula above 100 GeV. Compared to the quiescent state reported by VERITAS, this implies an increase by a factor of ~4. The previous record of VHE gamma-ray flux of this source was ~20% of the flux from the Crab nebula above 100 GeV. It was measured by VERITAS on the night of 30 January 2009 (2010ApJ, 709L, 163A). 1ES 1218+304 is a high-synchrotron-peaked BL Lac object located at redshift z=0.182. It was first recognized as a VHE gamma-ray emitter by the MAGIC Collaboration in 2005 (Albert, J., 2006, ApJ, 642L, 119A). The MAGIC observations were triggered by the flaring activity in the optical R-band, measured by the KVA telescope from 2018/12/24 to 2019/01/02. The KVA data showed a flux of 2.35+/-0.05 mJy on 2019/01/02, which is the highest optical flux measurement from this source in a time span of 15 years (http://users.utu.fi/kani/1m/1ES_1218+304_jy.html). MAGIC observations on 1ES 1218+304 will continue during the next weeks and multiwavelength observations are encouraged. The MAGIC contact persons for these observations are R. Mirzoyan (Razmik.Mirzoyan@mpp.mpg.de), V. Fallah Ramazani (vafara@utu.fi) and M. Cerruti (matteo.cerruti@icc.ub.edu). 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.

Gamma Ray ; >GeV ; TeV ; VHE ; AGN ; Blazar

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