Discovery of high-energy and very high energy γ-ray emission from the blazar RBS 0413

We report on the discovery of high-energy (HE; E > 0.1GeV) and very high energy (VHE; E > 100GeV) γ-ray emission from the high-frequency-peaked BL Lac object RBS0413. VERITAS, a ground-based γ-ray observatory, detected VHE γ rays from RBS0413 with a statistical significance of 5.5 standard deviations (σ) and a γ-ray flux of (1.5 ± 0.6 stat ± 0.7syst) × 10-8 photons m-2 s-1 (1% of the Crab Nebula flux) above 250GeV. The observed spectrum can be described by a power law with a photon index of 3.18 ± 0.68stat ± 0.30syst. Contemporaneous observations with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope detected HE γ rays from RBS0413 with a statistical significance of more than 9σ, a power-law photon index of 1.57 ± 0.12 stat +0.11 - 0.12sys, and a γ-ray flux between 300MeV and 300GeV of (1.64 ± 0.43stat +0.31 - 0.22sys) × 10-5 photons m-2 s -1. We present the results from Fermi-LAT and VERITAS, including a spectral energy distribution modeling of the γ-ray, quasi-simultaneous X-ray (Swift-XRT), ultraviolet (Swift-UVOT), and R-band optical (MDM) data. We find that, if conditions close to equipartition are required, both the combined synchrotron self-Compton/external-Compton and the lepto-hadronic models are preferred over a pure synchrotron self-Compton model. © 2012 The American Astronomical Society. All rights reserved.