A. U. Abeysekara, S. Archambault, A. Archer, T. Aune, A. Barnacka, W. Benbow, R. Bird, J. Biteau, J. H. Buckley, V. Bugaev, J. V. Cardenzana, M. Cerruti, X. Chen, J. L. Christiansen, L. Ciupik, M. P. Connolly, P. Coppi, W. Cui, H. J. Dickinson, J. DummJ. D. Eisch, M. Errando, A. Falcone, Q. Feng, J. P. Finley, H. Fleischhack, A. Flinders, P. Fortin, L. Fortson, A. Furniss, G. H. Gillanders, S. Griffin, J. Grube, G. Gyuk, M. Hütten, N. Håkansson, D. Hanna, J. Holder, T. B. Humensky, C. A. Johnson, P. Kaaret, P. Kar, N. Kelley-Hoskins, Y. Khassen, D. Kieda, M. Krause, F. Krennrich, S. Kumar, M. J. Lang, G. Maier, S. McArthur, A. McCann, K. Meagher, P. Moriarty, R. Mukherjee, D. Nieto, A. O.Faoláin De Bhróithe, R. A. Ong, A. N. Otte, N. Park, J. S. Perkins, A. Petrashyk, M. Pohl, A. Popkow, E. Pueschel, J. Quinn, K. Ragan, Gayle Ratliff, P. T. Reynolds, G. T. Richards, E. Roache, J. Rousselle, M. Santander, G. H. Sembroski, K. Shahinyan, A. W. Smith, D. Staszak, I. Telezhinsky, N. W. Todd, J. V. Tucci, J. Tyler, V. V. Vassiliev, S. Vincent, S. P. Wakely, O. M. Weiner, A. Weinstein, A. Wilhelm, D. A. Williams, B. Zitzer, P. S. Smith, T. W.S. Holoien, J. L. Prieto, C. S. Kochanek, K. Z. Stanek, B. Shappee, T. Hovatta, W. Max-Moerbeck, T. J. Pearson, R. A. Reeves, J. L. Richards, A. C.S. Readhead, G. M. Madejski, S. G. Djorgovski, A. J. Drake, M. J. Graham, A. Mahabal

Research output: Contribution to journalArticlepeer-review

77 Scopus citations


Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the universe. The detection of significant emission above 100 GeV from a distant quasar would show that some of the radiated gamma-rays escape pair-production interactions with low-energy photons, be it the extragalactic background light (EBL), or the radiation near the supermassive black hole lying at the jet's base. VERITAS detected gamma-ray emission up to ∼200 GeV from PKS 1441+25 (z = 0.939) during 2015 April, a period of high activity across all wavelengths. This observation of PKS 1441+25 suggests that the emission region is located thousands of Schwarzschild radii away from the black hole. The gamma-ray detection also sets a stringent upper limit on the near-ultraviolet to near-infrared EBL intensity, suggesting that galaxy surveys have resolved most, if not all, of the sources of the EBL at these wavelengths.

Original languageEnglish (US)
Article numberL22
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Dec 20 2015


  • cosmology: observations
  • diffuse radiation
  • gamma rays: galaxies
  • quasars: individual (PKS 1441+25=VER J1443+250)
  • radiation mechanisms: non-thermal

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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