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

E. Aliu, S. Archambault, T. Arlen, T. Aune, M. Beilicke, W. Benbow, M. Böttcher, A. Bouvier, S. M. Bradbury, J. H. Buckley, V. Bugaev, K. Byrum, A. Cannon, A. Cesarini, L. Ciupik, E. Collins-Hughes, M. P. Connolly, P. Coppi, W. Cui, G. DecerpritR. Dickherber, J. Dumm, M. Errando, A. Falcone, Q. Feng, J. P. Finley, G. Finnegan, L. Fortson, A. Furniss, N. Galante, D. Gall, S. Godambe, S. Griffin, J. Grube, G. Gyuk, D. Hanna, K. Hawkins, J. Holder, H. Huan, G. Hughes, T. B. Humensky, P. Kaaret, N. Karlsson, M. Kertzman, Y. Khassen, D. Kieda, H. Krawczynski, F. Krennrich, M. J. Lang, K. Lee

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45 Scopus citations


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.

Original languageEnglish (US)
Article number94
JournalAstrophysical Journal
Issue number2
StatePublished - May 10 2012


  • gamma rays: galaxies


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