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VERY HIGH ENERGY γ-RAYS from the UNIVERSE'S MIDDLE AGEMAGIC: DETECTION of the z = 0.940 BLAZAR PKS 1441+25 with MAGIC
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm, Sweden.
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, Stockholm, Sweden.
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Number of Authors: 246
2015 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 815, no 2, L23Article in journal (Refereed) Published
Abstract [en]

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 25.5σ 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 timescale 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.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015. Vol. 815, no 2, L23
Keyword [en]
cosmic background radiation, galaxies, active, galaxies, jets, gamma rays, galaxies, quasars, individual (PKS 1441+25)
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:kth:diva-181908DOI: 10.1088/2041-8205/815/2/L23ISI: 000369081700007ScopusID: 2-s2.0-84951862019OAI: oai:DiVA.org:kth-181908DiVA: diva2:901569
Note

QC 20160208. QC 20160303

Available from: 2016-02-08 Created: 2016-02-08 Last updated: 2016-03-03Bibliographically approved

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