Deep Broadband Observations of the Distant Gamma-ray Blazar PKS 1424+240

• Published in: arXiv.org 2014-03
• Main Authors: Behera, B, Benbow, W, Berger, K, Bird, R, Biteau, J, Bugaev, V, Byrum, K, Cerruti, M, Ciupik, L, Cui, W, Errando, M, Federici, S, Feng, Q, Finley, J P, Fleischhack, H, tson, L, Furniss, A, Gillanders, G H, Griffiths, S T, Grube, J, Gyuk, G, Holder, J, Hughes, G, Humensky, T B, Johnson, C A, Kertzman, M, Kieda, D, Krennrich, F, Kumar, S, Madhavan, A S, Moriarty, P, Mukherjee, R, Nieto, D, A O'Faolain de Bhroithe, Ong, R A, Park, N, Popkow, A, Prokoph, H, Quinn, J, Ragan, K, Rajotte, J, Reyes, L C, Reynolds, P T, Richards, G T, Sembroski, G H, Staszak, D, Telezhinsky, I, Tucci, J V, Tyler, J, Weinstein, A, Welsing, R, Wilhelm, A, Williams, D A, The VERITAS Collaboration, Ajello, M, Albert, A, Baldini, L, Bissaldi, E, Bregeon, J, Buehler, R, Buson, S, Caliandro, G A, Cameron, R A, Caraveo, P A, Cavazzuti, E, Charles, E, Claus, R, Cutini, S, L Di Venere, Favuzzi, C, Franckowiak, A, Fusco, P, Gargano, F, Gasparrini, D, Grenier, I A, Kuss, M, Latronico, L, Loparco, F, Lubrano, P, Mayer, M, Michelson, P F, Mizuno, T, Morselli, A, Murgia, S, Nuss, E, Ohsugi, T, Ormes, J F, Piron, F, Raino, S, Razzano, M, Reimer, A, Ritz, S, Schaal, M, Sgro, C, Siskind, E J, Takahashi, H, Tibaldo, L, Troja, E, Vianello, G, Werner, M
• Format: Article
• Language: English
• Subjects: Broadband; Cosmic rays; Energy measurement; Flux; Gamma rays; Light curve; Photon absorption; Red shift; Spectra; Telescopes; X ray telescopes
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1403.4308

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 \(z\ge0.6035\), 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 hours of VERITAS observations from three years, a multiwavelength light curve and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1\(\pm0.3\))\(\times10^{-7}\) ph m\(^{-2}\)s\(^{-1}\) above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02\(\pm0.08\))\(\times10^{-7}\) ph m\(^{-2}\)s\(^{-1}\) above 120 GeV. The measured differential very high energy (VHE; \(E\ge100\) GeV) spectral indices are \(\Gamma=\)3.8\(\pm\)0.3, 4.3\(\pm\)0.6 and 4.5\(\pm\)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 longer than year timescales 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.