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arXiv · 1112.3312

Gamma-Ray Emission from Two Blazars Behind the Galactic Plane: B2013+370 & B2023+336

E. Kara·M. Errando·W. Max-Moerbeck·E. Aliu·M. Bottcher·P. Fortin·J. P. Halpern·R. Mukherjee·A. C. S. Readhead·J. L. Richards
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Abstract

B2013+370 and B2023+336 are two blazars at low-galactic latitude that were previously proposed to be the counterparts for the EGRET unidentified sources, 3EG J2016+3657 and 3EG J2027+3429. Gamma-ray emission associated with the EGRET sources has been detected by the Fermi Gamma-ray Space Telescope, and the two sources, 1FGL J2015.7+3708 and 1FGL J2027.6+3335, have been classified as unidentified in the 1-year catalog. This analysis of the Fermi-LAT data collected during 31 months reveals that the 1FGL sources are spatially compatible with the blazars, and are significantly variable, supporting the hypothesis of extragalactic origin for the gamma-ray emission. The gamma-ray light curves are compared with 15 GHz radio light curves from the 40-m telescope at the Owens Valley Radio Observatory (OVRO). Simultaneous variability is seen in both bands for the two blazar candidates. The study is completed with the X-ray analysis of 1FGL J2015.7+3708 using Swift observations that were triggered in August 2010 by a Fermi-detected flare. The resulting spectral energy distribution shows a two-component structure typical of blazars. We also identify a second source in the field of view of 1FGL J2027.6+3335 with similar characteristics to the known LAT pulsars. This study gives solid evidence favoring blazar counterparts for these two unidentified EGRET and Fermi sources, supporting the hypothesis that a number of unidentified gamma-ray sources at low galactic latitudes are indeed of extragalactic origin.

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E. Kara, M. Errando, W. Max-Moerbeck, E. Aliu, M. Bottcher, P. Fortin, J. P. Halpern, R. Mukherjee, A. C. S. Readhead, J. L. Richards. 2011-12-14. Gamma-Ray Emission from Two Blazars Behind the Galactic Plane: B2013+370 & B2023+336. https://doi.org/10.1088/0004-637x%2F746%2F2%2F159

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