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MAGIC detects a VHE flare from 4C +21.35 (PKS 1222+21)

ATel #2684; Mose Mariotti (INFN and Univ. of Padova) on behalf of the MAGIC Collaboration
on 19 Jun 2010; 01:19 UT
Credential Certification: Mosè Mariotti (mariotti@pd.infn.it)

Subjects: Gamma Ray, >GeV, TeV, AGN, Quasar

Referred to by ATel #: 2686, 2687, 2693, 5981, 6207

The MAGIC collaboration reports the detection of a very high gamma ray flare from the Flat Spectrum Radio Quasar 4C +21.35 (PKS 1222+21, z=0.432, RA: 12h24m54.4s DEC: +21d22m46s, J2000) at energies above 100 GeV. The observation was performed in stereoscopic mode during low intensity moon light using the two 17m diameter imaging Cherenkov telescopes on La Palma, Canary Islands, Spain, during 0.5 hours on MJD 55364 (June 17th 2010). The preliminary results indicate a significant gamma-ray signal of ~120 excess events corresponding to >8 sigma level above the background. The integral flux for gamma-rays with energies above 100 GeV is estimated to be at >=30% of the Crab nebula flux. 4C +21.35 has been recently found to be a very high energy (VHE) gamma-ray emitter in the 100-300 GeV band by analyzing public Fermi/LAT data (Neronov et al. ATel #2617), and at the end of April 2010 a bright flare in the energy band above 100 MeV was reported by Fermi/LAT and AGILE (ATel #2584, #2641) along with a flare in near infrared (MJD 55275, ATel #2626).This is the ground-based detection of this source at VHE by a Cherenkov instrument. MAGIC will continue to observe 4C+21.35 and multi-frequency observations are strongly encouraged.