Multiwavelength Observations of the Previously Unidentified Blazar RX J0648.7+1516
Creators: name: Aliu, E.
name: Aune, T.
name: Beilicke, M.
name: Benbow, W.
name: Böttcher, M.
name: Bouvier, A.
name: Bradbury, S. M.
name: Buckley, J. H.
name: Bugaev, V.
name: Cannon, A.
name: Cesarini, A.
name: Ciupik, L.
name: Connolly, M. P.
name: Cui, W.
name: Decerprit, G.
name: Dickherber, R.
name: Duke, C.
name: Errando, M.
name: Falcone, A.
name: Feng, Q.
name: Finnegan, G.
name: Fortson, L.
name: Furniss, A.
name: Galante, N.
name: Gall, D.
name: Gillanders, G. H.
name: Godambe, S.
name: Griffin, S.
name: Grube, J.
name: Gyuk, G.
name: Hanna, D.
name: Hivick, B.
name: Holder, J.
name: Huan, H.
name: Hughes, G.
name: Hui, C. M.
name: Humensky, T. B.
name: Kaaret, P.
name: Karlsson, N.
name: Kertzman, M.
name: Kieda, D.
name: Krawczynski, H.
name: Krennrich, F.
name: Maier, G.
name: Majumdar, P.
name: McArthur, S.
name: McCann, A.
name: Moriarty, P.
name: Mukherjee, R.
name: Nelson, T.
name: Ong, R. A.
name: Orr, M.
name: Otte, A. N.
name: Park, N.
name: Perkins, J. S.
name: Pichel, A.
name: Pohl, M.
name: Prokoph, H.
name: Quinn, J.
name: Ragan, K.
name: Reyes, L. C.
name: Reynolds, P. T.
name: Roache, E.
name: Rose, H. J.
name: Ruppel, J.
name: Saxon, D. B.
name: Sembroski, G. H.
name: Skole, C.
name: Smith, A. W.
name: Staszak, D.
name: Tesic, G.
name: Theiling, M.
name: Thibadeau, S.
name: Tsurusaki, K.
name: Tyler, J.
name: Varlotta, A.
name: Vassiliev, V. V.
name: Wakely, S. P.
name: Weekes, T. C.
name: Weinstein, A.
name: Williams, D. A.
name: Zitzer, B.
name: Ciprini, S.
name: Fumagalli, M.
name: Kaplan, K.
name: Paneque, D.
name: Prochaska, J. X.
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report on the VERITAS discovery of very-high-energy (VHE) gamma- ray emission above 200 GeV from the high-frequency-peaked BL Lac object RXJ0648.7+1516 (GBJ0648+1516), associated with 1FGLJ0648.8+1516. The photon spectrum above 200 GeV is fit by a power law dN/dE = F0(E/E0)-Γ with a photon index Γ of 4.4 {\pm} 0.8stat {\pm}0.3syst and a flux normalization F0 of (2.3 {\pm}0.5stat {\pm} 1.2sys) {\times} 10-11 TeV-1cm-2s-1 with E0 = 300 GeV. No VHE vari- ability is detected during VERITAS observations of RXJ0648.7+1516 between 2010 March 4 and April 15. Following the VHE discovery, the optical identifica- tion 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 sub-classify the blazar as a high-frequency-peaked BL Lac (HBL) object, including data from the MDM ob- servatory, Swift-UVOT and XRT, and continuous monitoring at photon energies above 1 GeV 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 model (SSC) overproduces the high-energy gamma-ray emission measured by the Fermi-LAT over 2.3 years. The SED can be parameterized sat- isfactorily with an external-Compton or lepto-hadronic model, which have two and six additional free parameters, respectively, compared to the one-zone SSC model.