DISCOVERY OF VERY HIGH ENERGY GAMMA RAYS FROM PKS 1424+240 AND MULTIWAVELENGTH CONSTRAINTS ON ITS REDSHIFT
- Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)
- Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States)
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)
- Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States)
- Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada)
- Department of Physics, Washington University, St. Louis, MO 63130 (United States)
- Astrophysical Institute, Department of Physics and Astronomy, Ohio University, Athens, OH 45701 (United States)
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT (United Kingdom)
- Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439 (United States)
- School of Physics, University College Dublin, Belfield, Dublin 4, Republic of Ireland (Ireland)
- School of Physics, National University of Ireland, Galway, Republic of Ireland (Ireland)
- Astronomy Department, Adler Planetarium and Astronomy Museum, Chicago, IL 60605 (United States)
- Department of Physics, Purdue University, West Lafayette, IN 47907 (United States)
We report the first detection of very high energy{sup 83}Gamma-ray emission above 100 GeV. (VHE) gamma-ray emission above 140 GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum above 140 GeV measured by VERITAS is well described by a power law with a photon index of 3.8 {+-} 0.5{sub stat} {+-} 0.3{sub syst} and a flux normalization at 200 GeV of (5.1 {+-} 0.9{sub stat} {+-} 0.5{sub syst}) x 10{sup -11} TeV{sup -1} cm{sup -2} s{sup -1}, where stat and syst denote the statistical and systematical uncertainties, respectively. The VHE flux is steady over the observation period between MJD 54881 and 55003 (from 2009 February 19 to June 21). Flux variability is also not observed in contemporaneous high-energy observations with the Fermi Large Area Telescope. Contemporaneous X-ray and optical data were also obtained from the Swift XRT and MDM observatory, respectively. The broadband spectral energy distribution is well described by a one-zone synchrotron self-Compton model favoring a redshift of less than 0.1. Using the photon index measured with Fermi in combination with recent extragalactic background light absorption models it can be concluded from the VERITAS data that the redshift of PKS 1424+240 is less than 0.66.
- OSTI ID:
- 21301414
- Journal Information:
- Astrophysical Journal Letters, Vol. 708, Issue 2; Other Information: DOI: 10.1088/2041-8205/708/2/L100; Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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