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Very-high-energy gamma-rays from the Universe's middle age: detection of the z=0.940 blazar PKS 1441+25 with MAGIC

Ahnen, M. L. and Baloković, M. and Hovatta, T. (2015) Very-high-energy gamma-rays from the Universe's middle age: detection of the z=0.940 blazar PKS 1441+25 with MAGIC. Astrophysical Journal Letters, 815 (2). Art. No. L23. ISSN 2041-8205.

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The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5 {\sigma} using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 (z = 0.944), PKS 1441+25 is the most distant very high energy (VHE) blazar detected to date. The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi. Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. In the band covered by MAGIC, the variability time scale is estimated to be 6.4 +/- 1.9 days. Modeling the broadband spectral energy distribution with an external Compton model, the location of the emitting region is understood as originating in the jet outside the broad line region (BLR) during the period of high activity, while being partially within the BLR during the period of low (typical) activity. The observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy.

Item Type:Article
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Hovatta, T.0000-0002-2024-8199
Additional Information:© 2015. The American Astronomical Society. Received 2015 August 11; accepted 2015 November 22; published 2015 December 15. We would like to thank the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish MINECO (FPA2012-39502) and MECD (FPU13/00618), and the Japanese JSPS, and MEXT is gratefully acknowledged. This work was also supported by the Centro de Excelencia Severo Ochoa SEV-2012-0234, CPAN CSD2007-00042, and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 programme, by grant 268740 of the Academy of Finland, by the Croatian Science Foundation (HrZZ) Project 09/176 and the University of Rijeka Project, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N-HESS-MAGIC/2010/0. The Fermi-LAT Collaboration acknowledges support for LAT development, operation and data analysis from NASA and DOE (United States), CEA/Irfu and IN2P3/CNRS (France), ASI and INFN (Italy), MEXT, KEK, and JAXA (Japan), and the K.A. Wallenberg Foundation, the Swedish Research Council and the National Space Board (Sweden). Science analysis support in the operations phase from INAF (Italy) and CNES (France) is also gratefully acknowledged. We thank the Swift team duty scientists and science planners. L.P. acknowledges the PRIN-INAF 2014 financial support.
Funding AgencyGrant Number
Bundesministerium für Bildung und Forschung (BMBF)UNSPECIFIED
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Swiss National Fund (SNF)UNSPECIFIED
Ministerio de Economía y Competitividad (MINECO)FPA2012-39502
Ministerio de Educación, Cultura y Deporte (MECD)FPU13/00618
Centro de Excelencia Severo OchoaSEV-2012-0234
Consolider-Ingenio 2010 programmeUNSPECIFIED
Academy of Finland268740
Croatian Science Foundation09/176
University of Rijeka13.
Deutsche Forschungsgemeinschaft (DFG)SFB823/C4
Deutsche Forschungsgemeinschaft (DFG)SFB876/C3
Ministerstwo Nauki i Szkolnictwa Wyższego (MNiSzW)745/N-HESS-MAGIC/2010/0
K. A. Wallenberg FoundationUNSPECIFIED
Swedish National Space Board (SNSB)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Subject Keywords:cosmic background radiation; galaxies: active; galaxies: jets; gamma rays: galaxies; quasars: individual (PKS 1441+25)
Issue or Number:2
Record Number:CaltechAUTHORS:20160203-130137909
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Official Citation:M. L. Ahnen et al 2015 ApJ 815 L23
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64198
Deposited By: Joy Painter
Deposited On:03 Feb 2016 22:54
Last Modified:09 Mar 2020 13:18

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