TY - JOUR
T1 - H.E.S.S. and MAGIC observations of a sudden cessation of a very-high-energy γ -ray flare in PKS 1510-089 in May 2016
AU - Abdalla, H.
AU - Adam, R.
AU - Aharonian, F.
AU - Ait Benkhali, F.
AU - Angüner, E. O.
AU - Arcaro, C.
AU - Armand, C.
AU - Armstrong, T.
AU - Ashkar, H.
AU - Backes, M.
AU - Baghmanyan, V.
AU - Barbosa Martins, V.
AU - Barnacka, A.
AU - Barnard, M.
AU - Becherini, Y.
AU - Berge, D.
AU - Bernlöhr, K.
AU - Bi, B.
AU - Böttcher, M.
AU - Boisson, C.
AU - Bolmont, J.
AU - Bonnefoy, S.
AU - De Bony De Lavergne, M.
AU - Bregeon, J.
AU - Breuhaus, M.
AU - Brun, F.
AU - Brun, P.
AU - Bryan, M.
AU - Büchele, M.
AU - Bulik, T.
AU - Bylund, T.
AU - Caroff, S.
AU - Carosi, A.
AU - Casanova, S.
AU - Chand, T.
AU - Chandra, S.
AU - Chen, A.
AU - Cotter, G.
AU - Curyło, M.
AU - Damascene Mbarubucyeye, J.
AU - Davids, I. D.
AU - Davies, J.
AU - Deil, C.
AU - Devin, J.
AU - Dewilt, P.
AU - Dirson, L.
AU - Djannati-Ataï, A.
AU - Fallah Ramazani, V.
AU - Lähteenmäki, A.
AU - Tornikoski, M.
AU - MAGIC Collaboration
PY - 2021/4/7
Y1 - 2021/4/7
N2 - 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 γ rays must have been produced far down in the jet, where turbulent plasma crosses a standing shock.
AB - 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 γ rays must have been produced far down in the jet, where turbulent plasma crosses a standing shock.
KW - Galaxies: Active
KW - Quasars: Individual: Pks 1510-089
KW - Radiation mechanisms: Non-thermal
KW - Relativistic processes
UR - http://www.scopus.com/inward/record.url?scp=85104001652&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/202038949
DO - 10.1051/0004-6361/202038949
M3 - Article
AN - SCOPUS:85104001652
VL - 648
JO - Astronomy & Astrophysics
JF - Astronomy & Astrophysics
SN - 0004-6361
M1 - A23
ER -