VERITAS Detection of an Exceptional VHE Gamma-Ray Flare from the Blazar 1ES 1218+304

ATel #12360; Reshmi Mukherjee (Barnard College) for the VERITAS Collaboration
on 5 Jan 2019; 23:52 UT
Credential Certification: Reshmi Mukherjee (muk@astro.columbia.edu)

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The VERITAS Observatory reports the detection of a flare of very-high-energy (VHE; >100 GeV) gamma-ray flux from the blazar 1ES 1218+304 (12h21m21.941s, +30d10m37.11s, J2000.0) for observations made on January 3, 4 and 5, 2019. A preliminary analysis of the data indicates a peak gamma-ray flux greater than 20 % of the flux from the Crab nebula above 100 GeV. These observations were triggered by an elevated flux state detected during a regular snapshot observation by VERITAS and by the report of the detection of an unprecedented level of VHE flux from 1ES 1218+304 by the MAGIC telescopes [ATEL #12354]. 1ES 1218+304 was also seen to reach an unprecedented flux at X-ray energies, as detected with Swift-XRT for the last 4 days without any sign of decrease yet: https://www.swift.psu.edu/monitoring/source.php?source=1ES1218+304. As noted in ATel #12354, the KVA telescopes showed a flux that 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). Multiwavelength observations are encouraged.

Questions regarding the VERITAS observations should be directed to Reshmi Mukherjee (muk@astro.columbia.edu). VERITAS (Very Energetic Radiation Imaging Telescope Array System) is located at the Fred Lawrence Whipple Observatory in southern Arizona, USA, and is most sensitive to gamma rays between ~85 GeV and ~30 TeV (http://veritas.sao.arizona.edu).