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) × 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) × 10–7 photons m–2 s–1 above 120 GeV. The measured differential very high energy (VHE; E ≥ 100 GeV) spectral indices are Γ = 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 τ = 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.
Autori interni: | |
Autori: | S. Archambault;T. Aune;B. Behera;M. Beilicke;W. Benbow;K. Berger;R. Bird;J. Biteau;V. Bugaev;K. Byrum;J. V Cardenzana;M. Cerruti;X. Chen;L. Ciupik;M. P. Connolly;W. Cui;J. Dumm;M. Errando;A. Falcone;S. Federici;Q. Feng;J. P. Finley;H. Fleischhack;L. Fortson;A. Furniss;N. Galante;G. H. Gillanders;S. Griffin;S. T. Griffiths;J. Grube;G. Gyuk;D. Hanna;J. Holder;G. Hughes;T. B. Humensky;C. A. Johnson;P. Kaaret;M. Kertzman;Y. Khassen;D. Kieda;H. Krawczynski;F. Krennrich;S. Kumar;M. J. Lang;A. S Madhavan;G. Maier;A. McCann;K. Meagher;P. Moriarty;R. Mukherjee;D. Nieto;A. O'Faol?in de Bhr?ithe;R. A. Ong;A. N. Otte;N. Park;M. Pohl;A. Popkow;H. Prokoph;J. Quinn;K. Ragan;J. Rajotte;L. C. Reyes;P. T. Reynolds;G. T. Richards;E. Roache;G. H. Sembroski;K. Shahinyan;D. Staszak;I. Telezhinsky;J. V. Tucci;J. Tyler;A. Varlotta;V. V. Vassiliev;S. Vincent;S. P. Wakely;A. Weinstein;R. Welsing;A. Wilhelm;D. A. Williams;M. Ackermann;M. Ajello;A. Albert;L. Baldini;D. Bastieri;R. Bellazzini;E. Bissaldi;J. Bregeon;R. Buehler;S. Buson;G. A. Caliandro;R. A. Cameron;P. A. Caraveo;E. Cavazzuti;E. Charles;J. Chiang;S. Ciprini;R. Claus;S. Cutini;F. D'Ammando;A. de Angelis;F. de Palma;C. D. Dermer;S. W. Digel;L. Di Venere;P. S. Drell;C. Favuzzi;A. Franckowiak;P. Fusco;F. Gargano;D. Gasparrini;N. Giglietto;F. Giordano;M. Giroletti;I. A. Grenier;S. Guiriec;T. Jogler;M. Kuss;S. Larsson;L. Latronico;F. Longo;F. Loparco;P. Lubrano;G. M. Madejski;M. Mayer;M. N. Mazziotta;P. F. Michelson;T. Mizuno;M. E. Monzani;A. Morselli;S. Murgia;E. Nuss;T. Ohsugi;J. F. Ormes;D. Paneque;J. S. Perkins;F. Piron;G. Pivato;S. Rain?;M. Razzano;A. Reimer;O. Reimer;S. Ritz;M. Schaal;C. Sgr?;E. J. Siskind;P. Spinelli;H. Takahashi;L. Tibaldo;M. Tinivella;E. Troja;G. Vianello;M. Werner;M. Wood |
Titolo: | DEEP BROADBAND OBSERVATIONS OF THE DISTANT GAMMA-RAY BLAZAR PKS 1424+240 |
Anno del prodotto: | 2014 |
Digital Object Identifier (DOI): | 10.1088/2041-8205/785/1/L16 |
Appare nelle tipologie: | 1.1 Articolo in rivista |