MULTIWAVELENGTH OBSERVATIONS OF THE PREVIOUSLY UNIDENTIFIED BLAZAR RX J0648.7+1516

Journal Article · Thu Dec 01 00:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/742/2/127· OSTI ID:22004599

Aliu, E; Errando, M ^[1]; Aune, T; Bouvier, A ^[2]; Beilicke, M; Buckley, J H; Bugaev, V; Dickherber, R ^[3]; Benbow, W ^[4]; Boettcher, M ^[5]; Bradbury, S M ^[6]; Cannon, A ^[7]; Cesarini, A; Connolly, M P ^[8]; Ciupik, L ^[9]; Cui, W; Feng, Q ^[10]; Decerprit, G ^[11]; Duke, C ^[12]; Falcone, A ^[13] ; others, and

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1. Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States)
2. Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States)
3. Department of Physics, Washington University, St. Louis, MO 63130 (United States)
4. Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)
5. Astrophysical Institute, Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States)
6. School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom)
7. School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)
8. School of Physics, National University of Ireland Galway, University Road, Galway (Ireland)
9. Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States)
10. Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)
11. DESY, Platanenallee 6, D-15738 Zeuthen (Germany)
12. Department of Physics, Grinnell College, Grinnell, IA 50112-1690 (United States)
13. Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States)

We report on the VERITAS discovery of very high energy (VHE) gamma-ray emission above 200 GeV from the high-frequency-peaked BL Lac (HBL) object RX J0648.7+1516 (GB J0648+1516), associated with 1FGL J0648.8+1516. The photon spectrum above 200 GeV is fitted by a power law dN/dE = F{sub 0}(E/E{sub 0}){sup -{Gamma}} with a photon index {Gamma} of 4.4 {+-} 0.8{sub stat} {+-} 0.3{sub syst} and a flux normalization F{sub 0} of (2.3 {+-} 0.5{sub stat} {+-} 1.2{sub sys}) Multiplication-Sign 10{sup -11} TeV{sup -1} cm{sup -2} s{sup -1} with E{sub 0} = 300 GeV. No VHE variability is detected during VERITAS observations of RX J0648.7+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 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 (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.

• OSTI ID: 22004599
• Journal Information: Astrophysical Journal, Vol. 742, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
BL LACERTAE OBJECTS
ENERGY SPECTRA
GALAXIES
GAMMA RADIATION
HADRONS
PHOTONS
RED SHIFT
TELESCOPES