Multiwavelength observations of the previously unidentified blazar RX J0648.7+1516

  • E. Aliu
  • , T. Aune
  • , M. Beilicke
  • , W. Benbow
  • , M. Böttcher
  • , A. Bouvier
  • , S. M. Bradbury
  • , J. H. Buckley
  • , V. Bugaev
  • , A. Cannon
  • , A. Cesarini
  • , L. Ciupik
  • , M. P. Connolly
  • , W. Cui
  • , G. Decerprit
  • , R. Dickherber
  • , C. Duke
  • , M. Errando
  • , A. Falcone
  • , Q. Feng
  • G. Finnegan, L. Fortson, A. Furniss, N. Galante, D. Gall, G. H. Gillanders, S. Godambe, S. Griffin, J. Grube, G. Gyuk, D. Hanna, B. Hivick, J. Holder, H. Huan, G. Hughes, C. M. Hui, T. B. Humensky, P. Kaaret, N. Karlsson, M. Kertzman, D. Kieda, H. Krawczynski, F. Krennrich, G. Maier, P. Majumdar, S. McArthur, A. McCann, P. Moriarty, R. Mukherjee, T. Nelson

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

We report on the VERITAS discovery of very high energy (VHE) gamma-ray emission above 200GeV from the high-frequency-peaked BL Lac (HBL) object RXJ0648.7+1516 (GBJ0648+1516), associated with 1FGLJ0648.8+1516. The photon spectrum above 200GeV is fitted by a power law dN/dE = F 0(E/E 0) with a photon index Γ of 4.4 ± 0.8stat± 0.3syst and a flux normalization F 0 of (2.3± 0.5stat± 1.2sys) × 10-11TeV-1cm-2 s-1 with E 0 = 300GeV. No VHE variability is detected during VERITAS observations of RXJ0648.7+1516 between 2010 March 4 and April 15. Following the VHE discovery, the optical identification and spectroscopic redshift were obtained using the Shane 3 m Telescope at the Lick Observatory, showing the unidentified object to be a BL Lac type with a redshift of z = 0.179. Broadband multiwavelength observations contemporaneous with the VERITAS exposure period can be used to subclassify the blazar as an HBL object, including data from the MDM observatory, Swift-UVOT, and X-Ray Telescope, and continuous monitoring at photon energies above 1GeV from the Fermi Large Area Telescope (LAT). We find that in the absence of undetected, high-energy rapid variability, the one-zone synchrotron self-Compton (SSC) model overproduces the high-energy gamma-ray emission measured by the Fermi-LAT over 2.3 years. The spectral energy distribution can be parameterized satisfactorily with an external-Compton or lepto-hadronic model, which have two and six additional free parameters, respectively, compared to the one-zone SSC model.

Original languageEnglish (US)
Article number127
JournalAstrophysical Journal
Volume742
Issue number2
DOIs
StatePublished - Dec 1 2011

Keywords

  • gamma rays: galaxies

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