Deep Broadband Observations of the Distant Gamma-ray Blazar PKS 1424+240
Creators: name: Archambault, S.
name: Aune, T.
name: Behera, B.
name: Beilicke, M.
name: Benbow, W.
name: Berger, K.
name: Bird, R.
name: Biteau, J.
name: Bugaev, V.
name: Byrum, K.
name: Cardenzana, J. V
name: Cerruti, M.
name: Chen, X.
name: Ciupik, L.
name: Connolly, M. P.
name: Cui, W.
name: Dumm, J.
name: Errando, M.
name: Falcone, A.
name: Federici, S.
name: Feng, Q.
name: Finley, J. P.
name: Fleischhack, H.
name: Fortson, L.
name: Furniss, A.
name: Galante, N.
name: Gillanders, G. H.
name: Griffin, S.
name: Griffiths, S. T.
name: Grube, J.
name: Gyuk, G.
name: Hanna, D.
name: Holder, J.
name: Hughes, G.
name: Humensky, T. B.
name: Johnson, C. A.
name: Kaaret, P.
name: Kertzman, M.
name: Khassen, Y.
name: Kieda, D.
name: Krawczynski, H.
name: Krennrich, F.
name: Kumar, S.
name: Lang, M. J.
name: Madhavan, A. S
name: Maier, G.
name: McCann, A.
name: Meagher, K.
name: Moriarty, P.
name: Mukherjee, R.
name: Nieto, D.
name: de Bhroithe, A. O'Faolain
name: Ong, R. A.
name: Otte, A. N.
name: Park, N.
name: Pohl, M.
name: Popkow, A.
name: Prokoph, H.
name: Quinn, J.
name: Ragan, K.
name: Rajotte, J.
name: Reyes, L. C.
name: Reynolds, P. T.
name: Richards, G. T.
name: Roache, E.
name: Sembroski, G. H.
name: Shahinyan, K.
name: Staszak, D.
name: Telezhinsky, I.
name: Tucci, J. V.
name: Tyler, J.
name: Varlotta, A.
name: Vassiliev, V. V.
name: Vincent, S.
name: Wakely, S. P.
name: Weinstein, A.
name: Welsing, R.
name: Wilhelm, A.
name: Williams, D. A.
name: Ackermann, M.
name: Ajello, M.
name: Albert, A.
name: Baldini, L.
name: Bastieri, D.
name: Bellazzini, R.
name: Bissaldi, E.
name: Bregeon, J.
name: Buehler, R.
name: Buson, S.
name: Caliandro, G. A.
name: Cameron, R. A.
name: Caraveo, P. A.
name: Cavazzuti, E.
name: Charles, E.
name: Chiang, J.
name: Ciprini, S.
name: Claus, R.
name: Cutini, S.
name: D'Ammando, F.
name: de Angelis, A.
name: de Palma, F.
name: Dermer, C. D.
name: Digel, S. W.
name: Di Venere, L.
name: Drell, P. S.
name: Favuzzi, C.
name: Franckowiak, A.
name: Fusco, P.
name: Gargano, F.
name: Gasparrini, D.
name: Giglietto, N.
name: Giordano, F.
name: Giroletti, M.
name: Grenier, I. A.
name: Guiriec, S.
name: Jogler, T.
name: Kuss, M.
name: Larsson, S.
name: Latronico, L.
name: Longo, F.
name: Loparco, F.
name: Lubrano, P.
name: Madejski, G. M.
name: Mayer, M.
name: Mazziotta, M. N.
name: Michelson, P. F.
name: Mizuno, T.
name: Monzani, M. E.
name: Morselli, A.
name: Murgia, S.
name: Nuss, E.
name: Ohsugi, T.
name: Ormes, J. F.
name: Perkins, J. S.
name: Piron, F.
name: Pivato, G.
name: Raino, S.
name: Razzano, M.
name: Reimer, A.
name: Reimer, O.
name: Ritz, S.
name: Schaal, M.
name: Sgro, C.
name: Siskind, E. J.
name: Spinelli, P.
name: Takahashi, H.
name: Tibaldo, L.
name: Tinivella, M.
name: Troja, E.
name: Vianello, G.
name: Werner, M.
name: Wood, M.
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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 $Γ=$3.8$\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 $τ=2$, 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.
description: ApJL accepted March 17, 2014