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VERITAS Discovery of Very High-Energy Gamma-Ray Emission from RGB J2243+203

ATel #6849; Jamie Holder (for the VERITAS Collaboration)
on 24 Dec 2014; 23:09 UT
Credential Certification: Jamie Holder (jholder@physics.udel.edu)

Subjects: X-ray, Gamma Ray, >GeV, TeV, VHE, AGN

The VERITAS Collaboration reports the discovery of very high energy (VHE; E>100 GeV) gamma-ray emission above 180 GeV from the radio and X-ray blazar RGB J2243+203. This source is consistent with the hard Fermi-LAT gamma-ray source 1FHL J2244.0+2020 (RA 341.004 , dec +20.343), highlighted as a candidate TeV source in the 1FHL catalog (Ackermann et al. 2013, ApJS, 209, 34). VERITAS, an atmospheric-Cherenkov telescope array detected ~190 gamma rays with 4 hours of exposure between 21 Dec 2014 and 24 Dec 2014 (UT), corresponding to a statistical significance of 5.7 standard deviations. Preliminary analysis shows the source to display a ~4% Crab Nebula flux above 180 GeV. The redshift of the source is unknown, with an estimate of z>0.39 based on optical imaging (Meisner & Romani 2010, ApJ, 712, 14). The source, classified as an intermediate-energy-peaked BL Lac object in Laurent-Muehleisen et al. 1999, ApJL, 525, 127 and a high-synchrotron-peaked BL Lac object in the 1FHL catalog, was identified by VERITAS as a promising candidate for VHE emission this month based upon a marginally elevated 1-100 GeV flux state observed in an automated daily analysis of Fermi-LAT observations. The Fermi-LAT source is reported in the 1FHL catalog as having a photon index of 2.38+- 0.23 above 10 GeV and a flux between 10 and 500 GeV of (52.1+-7.9) e-11 cm^-2 s^-1.

A request for ToO observations with Swift has been approved. Observations at other wavelengths and efforts to determine the redshift of this object are encouraged. Questions regarding the VERITAS observations should be directed to Jamie Holder (jholder@physics.udel.edu).