Discovery of Very High Energy Gamma Rays from PKS 1424+240 and Multiwavelength Constraints on its Redshift

Technical Report · Thu Apr 05 00:00:00 EDT 2012

DOI:https://doi.org/10.2172/1046386· OSTI ID:1046386

Aliu, E. ^[1]; Arlen, T. ^[2]; Aune, T. ^[3]; Bautista, M. ^[4]; Benbow, W. ^[5]; Böttcher, M. ^[6]; Boltuch, D. ^[1]; Bradbury, S. M. ^[7]; Buckley, J. H. ^[8]; Bugaev, V. ^[8]; Byrum, K. ^[9]; Cannon, A. ^[10]; Cesarini, A. ^[11]; Chow, Y. C. ^[12]; Ciupik, L. ^[13]; Cogan, P. ^[4]; Cui, W. ^[14]; Duke, C. ^[15]; Falcone, A. ^[16]; Otte, A. N. ^[17] ; Furniss, A. ^[17]; Chiang, J. ^[18]; Acciari, V. A. ^[19]

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1. Univ. of Delaware, Newark, DE (United States)
2. Univ. of California, Los Angeles, CA (United States)
3. Univ. of California, Santa Cruz, CA (United States)
4. McGill Univ., Montreal, QC (Canada)
5. Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ (United States)
6. Ohio Univ., Athens, OH (United States)
7. Univ. of Leeds, Leeds (United Kingdom)
8. Washington Univ., St. Louis, MO (United States)
9. Argonne National Laboratory (ANL), Argonne, IL (United States)
10. Univ. College Dublin, Dublin (Ireland)
11. National University of Ireland, Dublin (Ireland)
12. University of California, Los Angeles, CA (United States)
13. Adler Planetarium and Astronomy Museum, Chicago, IL (United States)
14. Purdue Univ., West Lafayette, IN (United States)
15. Grinnell College, IA (United States)
16. Pennsylvania State Univ., University Park, PA (United States)
17. University of California, Santa Cruz, CA (United States)
18. Stanford Univ., CA (United States). Stanford University Energy Modeling Forum
19. Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ (United States); VERITAS Collaboration. et al.

We report the first detection of very-high-energy (VHE) gamma-ray emission above 140GeV from PKS 1424+240, a BL Lac object with an unknown redshift. The photon spectrum above 140GeV measured by VERITAS is well described by a power law with a photon index of 3.8 {+-}0.5_stat {+-} 0.3_syst and a flux normalization at 200 GeV of (5.1 {+-} 0.9_stat {+-} 0.5_syst) x 10^-11 TeV^-1 cm^-2 s^-1, where stat and syst denote the statistical and systematical uncertainty, respectively. The VHE flux is steady over the observation period between MJD 54881 and 55003 (2009 February 19 to June 21). Flux variability is also not observed in contemporaneous high energy observations with the Fermi Large Area Telescope (LAT). Contemporaneous X-ray and optical data were also obtained from the Swift XRT and MDM observatory, respectively. The broadband spectral energy distribution (SED) is well described by a one-zone synchrotron self-Compton (SSC) model favoring a redshift of less than 0.1. Using the photon index measured with Fermi in combination with recent extragalactic background light (EBL) absorption models it can be concluded from the VERITAS data that the redshift of PKS 1424+240 is less than 0.66.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 1046386
• Report Number(s): SLAC-PUB--14913; arXiv:0912.0730
• Country of Publication: United States
• Language: English

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