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