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Archambault, S,Aune, T,Behera, B,Beilicke, M,Benbow, W,Berger, K,Bird, R,Biteau, J,Bugaev, V,Byrum, K,Cardenzana, JV,Cerruti, M,Chen, X,Ciupik, L,Connolly, MP,Cui, W,Dumm, J,Errando, M,Falcone, A,Federici, S,Feng, Q,Finley, JP,Fleischhack, H,Fortson, L,Furniss, A,Galante, N,Gillanders, GH,Griffin, S,Griffiths, ST,Grube, J,Gyuk, G,Hanna, D,Holder, J,Hughes, G,Humensky, TB,Johnson, CA,Kaaret, P,Kertzman, M,Khassen, Y,Kieda, D,Krawczynski, H,Krennrich, F,Kumar, S,Lang, MJ,Madhavan, AS,Maier, G,McCann, A,Meagher, K,Moriarty, P,Mukherjee, R,Nieto, D,de Bhroithe, AO,Ong, RA,Otte, AN,Park, N,Pohl, M,Popkow, A,Prokoph, H,Quinn, J,Ragan, K,Rajotte, J,Reyes, LC,Reynolds, PT,Richards, GT,Roache, E,Sembroski, GH,Shahinyan, K,Staszak, D,Telezhinsky, I,Tucci, JV,Tyler, J,Varlotta, A,Vassiliev, VV,Vince
2014
April
Astrophysical Journal Letters
DEEP BROADBAND OBSERVATIONS OF THE DISTANT GAMMA-RAY BLAZAR PKS 1424+240
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BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation gamma rays: galaxies EXTRAGALACTIC BACKGROUND LIGHT SPACE-TELESCOPE MISSION LARGE-AREA TELESCOPE ENERGY COSMIC-RAY TEV BLAZARS SPECTRA REDSHIFT ABSORPTION RADIATION UNIVERSE
785
We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z >= 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 +/- 0.3) x 10(-7) photons m(-2) s(-1) above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02 +/- 0.08) x 10-7 photons m(-2) s(-1) above 120 GeV. The measured differential very high energy (VHE; E >= 100 GeV) spectral indices are Gamma = 3.8 +/- 0.3, 4.3 +/- 0.6 and 4.5 +/- 0.2 in 2009, 2011, and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than tau = 2, where it is postulated that any variability would be small and occur on timescales longer than a year if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics.
10.1088/2041-8205/785/1/L16
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