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HESS and MAGIC observations of a sudden cessation of a very-high-energy gamma-ray flare in PKS 1510-089 in May 2016
North West Univ, South Africa.
Inst Polytech Paris, France.
Max Planck Inst Kernphys, Germany;Dublin Inst Adv Studies,Ireland;RAU, Armenia.
Max Planck Inst Kernphys, Germany.
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Number of Authors: 4262021 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 648, article id A23Article in journal (Refereed) Published
Abstract [en]

The flat spectrum radio quasar (FSRQ) PKS 1510-089 is known for its complex multiwavelength behaviour and it is one of only a few FSRQs detected in very-high-energy (VHE, E>100 GeV) gamma rays. The VHE gamma -ray observations with H.E.S.S. and MAGIC in late May and early June 2016 resulted in the detection of an unprecedented flare, which revealed, for the first time, VHE gamma -ray intranight variability for this source. While a common variability timescale of 1.5 h has been found, there is a significant deviation near the end of the flare, with a timescale of similar to 20 min marking the cessation of the event. The peak flux is nearly two orders of magnitude above the low-level emission. For the first time, a curvature was detected in the VHE gamma -ray spectrum of PKS 1510-089, which can be fully explained by the absorption on the part of the extragalactic background light. Optical R-band observations with ATOM revealed a counterpart of the gamma -ray flare, even though the detailed flux evolution differs from the VHE gamma -ray light curve. Interestingly, a steep flux decrease was observed at the same time as the cessation of the VHE gamma -ray flare. In the high-energy (HE, E> 100 MeV) gamma -ray band, only a moderate flux increase was observed with Fermi-LAT, while the HE gamma -ray spectrum significantly hardens up to a photon index of 1.6. A search for broad-line region (BLR) absorption features in the gamma -ray spectrum indicates that the emission region is located outside of the BLR. Radio very-long-baseline interferometry observations reveal a fast-moving knot interacting with a standing jet feature around the time of the flare. As the standing feature is located similar to 50 pc from the black hole, the emission region of the flare may have been located at a significant distance from the black hole. If this is indeed a true correlation, the VHE gamma rays must have been produced far down in the jet, where turbulent plasma crosses a standing shock.

Place, publisher, year, edition, pages
EDP Sciences, 2021. Vol. 648, article id A23
Keywords [en]
radiation mechanisms: non-thermal, quasars: individual: PKS 1510-089, galaxies: active, relativistic processes
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics, Astroparticle Physics
Identifiers
URN: urn:nbn:se:lnu:diva-103706DOI: 10.1051/0004-6361/202038949ISI: 000638124500009Scopus ID: 2-s2.0-85104001652OAI: oai:DiVA.org:lnu-103706DiVA, id: diva2:1559696
Available from: 2021-06-02 Created: 2021-06-02 Last updated: 2024-10-18Bibliographically approved

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Becherini, YvonneBylund, TomasPunch, MichaelSenniappan, Mohanraj

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