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oai:recercat.cat:2445/2210932025-12-05T16:45:52Zcom_2072_1057col_2072_478823col_2072_478917

HESS and MAGIC observations of a sudden cessation of a very-high-energy <em>γ</em>-ray flare in PKS 1510-089 in May 2016 Cerruti, Matteo Molina, Edgar Paredes i Poy, Josep Maria Ribó Gomis, Marc MAGIC Collaboration Galàxies actives Radiació Quàsars Active galaxies Radiation Quasars 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) γ rays. The VHE γ-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 γ-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∼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 γ-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 γ-ray flare, even though the detailed flux evolution differs from the VHE γ-ray light curve. Interestingly, a steep flux decrease was observed at the same time as the cessation of the VHE γ-ray flare. In the high-energy (HE, E >100 MeV) γ-ray band, only a moderate flux increase was observed with Fermi-LAT, while the HE γ-ray spectrum significantly hardens up to a photon index of 1.6. A search for broad-line region (BLR) absorption features in the γ-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∼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 γrays must have been produced far down in the jet, where turbulent plasma crosses a standing shock. 2025-05-16T16:53:46Z 2025-05-16T16:53:46Z 2021-04-07 2025-05-16T16:53:46Z info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Reproducció del document publicat a: https://doi.org/10.1051/0004-6361/202038949 Astronomy & Astrophysics, 2021, vol. 648 https://doi.org/10.1051/0004-6361/202038949 (c) The European Southern Observatory (ESO), 2021 info:eu-repo/semantics/openAccess EDP Sciences Articles publicats en revistes (Física Quàntica i Astrofísica)