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Deep broadband observations of the distant gamma-ray blazar PKS 1424+240

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, Xuhui Chen, L. Ciupik, M. P. Connolly, Wei Cui, J. Dumm, M. Errando, A. Falcone, Simone 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, Daniel Nieto, R. A. Ong, A. N. Otte, N. Park, Martin 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, Igor Telezhinsky, J. V. Tucci, J. Tyler, A. Varlotta, V. V. Vassiliev, S. Vincent, S. P. Wakely, A. Weinstein, R. Welsing, Alina Wilhelm, D. A. Williams, Margit 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, 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, Aldo Morselli, S. Murgia, E. Nuss, T. Ohsugi, J. F. Ormes, D. Paneque, J. S. Perkins, F. Piron, G. Pivato, S. Raino, M. Razzano, A. Reimer, Olaf Reimer, S. Ritz, M. Schaal, C. Sgro, E. J. Siskind, P. Spinelli, H. Takahashi, L. Tibaldo, M. Tinivella, E. Troja, G. Vianello, M. Werner, M. Wood

  • 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 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.show moreshow less

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Author: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, Xuhui Chen, L. Ciupik, M. P. Connolly, Wei Cui, J. Dumm, M. Errando, A. Falcone, Simone FedericiGND, 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, Daniel Nieto, R. A. Ong, A. N. Otte, N. Park, Martin PohlORCiDGND, 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, Igor Telezhinsky, J. V. Tucci, J. Tyler, A. Varlotta, V. V. Vassiliev, S. Vincent, S. P. Wakely, A. Weinstein, R. Welsing, Alina Wilhelm, D. A. Williams, Margit 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, 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, Aldo Morselli, S. Murgia, E. Nuss, T. Ohsugi, J. F. Ormes, D. Paneque, J. S. Perkins, F. Piron, G. Pivato, S. Raino, M. Razzano, A. Reimer, Olaf Reimer, S. Ritz, M. Schaal, C. Sgro, E. J. Siskind, P. Spinelli, H. Takahashi, L. Tibaldo, M. Tinivella, E. Troja, G. Vianello, M. Werner, M. Wood
DOI:https://doi.org/10.1088/2041-8205/785/1/L16
ISSN:2041-8205 (print)
ISSN:2041-8213 (online)
Parent Title (English):The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
Publisher:IOP Publ. Ltd.
Place of publication:Bristol
Document Type:Article
Language:English
Year of first Publication:2014
Year of Completion:2014
Creating Corporation:VERITAS Collaboration, Fermi LAT Collaboration
Release Date:2017/03/27
Tag:BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation; gamma rays: galaxies
Volume:785
Issue:1
Pagenumber:8
Funder:U.S. Department of Energy Office of Science; U.S. National Science Foundation; Smithsonian Institution; NSERC in Canada; Science Foundation Ireland [SFI 10/RFP/AST2748]; STFC in the UK; NASA through the Space Telescope Science Institute [HST-GO-12863]; NASA [NAS 5-26555]; INAF in Italy; CNES in France
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert