A fast, very-high-energy <i>γ</i>-ray flare from BL Lacertae during a period of multi-wavelength activity in June 2015
V. A. AcciariInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainStefano AnsoldiDepartment of Physics, Kyoto University, 606-8502 Kyoto, JapanL. A. AntonelliNational Institute for Astrophysics (INAF), 00136 Rome, ItalyA. Arbet EngelsETH Zurich, 8093 Zurich, SwitzerlandDominik BaackTechnische Universität Dortmund, 44221 Dortmund, GermanyA. BabićCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaB. BanerjeeSaha Institute of Nuclear Physics, HBNI, 1/AF Bidhannagar, Salt Lake, Sector-1, Kolkata 700064, IndiaP. BangaleMax-Planck-Institut für Physik, 80805 München, GermanyU. Barres de AlmeidaCentro Brasileiro de Pesquisas Físicas (CBPF), 22290-180 URCA, Rio de Janeiro (RJ), BrasilJ. A. BarrioUnidad de Partículas y Cosmología (UPARCOS), Universidad Complutense, 28040 Madrid, SpainJ. Becerra GonzálezInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainW. BednarekUniversity of ᴌódź, Department of Astrophysics, 90236 ᴌódź, PolandE. BernardiniHumboldt University of Berlin, Institut für Physik, 12489 Berlin, GermanyA. BertiDipartimento di Fisica, Università di Trieste, 34127 Trieste, ItalyJürgen BesenriederMax-Planck-Institut für Physik, 80805 München, GermanyW. BhattacharyyaDeutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, GermanyC. BigongiariNational Institute for Astrophysics (INAF), 00136 Rome, ItalyA. BilandETH Zurich, 8093 Zurich, SwitzerlandO. BlanchInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainG. BonnoliUniversità di Siena and INFN Pisa, 53100 Siena, ItalyR. CarosiUniversità di Pisa, and INFN Pisa, 56126 Pisa, ItalyG. CeribellaMax-Planck-Institut für Physik, 80805 München, GermanyS. CikotaCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaS. M. ColakInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainP. ColinMax-Planck-Institut für Physik, 80805 München, GermanyE. ColomboInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainJ. L. ContrerasUnidad de Partículas y Cosmología (UPARCOS), Universidad Complutense, 28040 Madrid, SpainJ. CortinaInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainS. CovinoNational Institute for Astrophysics (INAF), 00136 Rome, ItalyV. D’EliaNational Institute for Astrophysics (INAF), 00136 Rome, ItalyP. Da VelaUniversità di Pisa, and INFN Pisa, 56126 Pisa, ItalyF. DazziNational Institute for Astrophysics (INAF), 00136 Rome, ItalyA. De AngelisUniversità di Padova and INFN, 35131 Padova, ItalyB. De LottoUniversità di Udine, and INFN Trieste, 33100 Udine, ItalyM. DelfinoPort d'Informació Científica (PIC), 08193 Bellaterra (Barcelona), SpainJ. DelgadoInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainF. Di PierroInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainE. Do Souto EspiñeraInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainA. DomínguezUnidad de Partículas y Cosmología (UPARCOS), Universidad Complutense, 28040 Madrid, SpainD. Dominis PresterCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaD. DornerUniversität Würzburg, 97074 Würzburg, GermanyM. DoroUniversità di Padova and INFN, 35131 Padova, ItalyS. EineckeTechnische Universität Dortmund, 44221 Dortmund, GermanyD. ElsäesserTechnische Universität Dortmund, 44221 Dortmund, GermanyV. Fallah RamazanıFinnish MAGIC Consortium: Tuorla Observatory and Finnish Centre of Astronomy with ESO (FINCA), University of Turku FIN-20014 University of Turku, Finland, Astronomy Division, University of Oulu, 90014, University of Oulu, FinlandAlicia FattoriniTechnische Universität Dortmund, 44221 Dortmund, GermanyA. Fernández-BarralUniversità di Padova and INFN, 35131 Padova, ItalyG. FerraraNational Institute for Astrophysics (INAF), 00136 Rome, ItalyD. FidalgoUnidad de Partículas y Cosmología (UPARCOS), Universidad Complutense, 28040 Madrid, SpainL. FoffanoUniversità di Padova and INFN, 35131 Padova, ItalyM. V. FonsecaUnidad de Partículas y Cosmología (UPARCOS), Universidad Complutense, 28040 Madrid, SpainL. FontDepartament de Física, and CERES-IEEC, Universitat Autónoma de Barcelona, 08193 Bellaterra, SpainC. FruckMax-Planck-Institut für Physik, 80805 München, GermanyD. GalindoUniversitat de Barcelona, ICCUB, IEEC-UB, 08028 Barcelona, SpainS. GallozziNational Institute for Astrophysics (INAF), 00136 Rome, ItalyR. J. Garcı́a LópezInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainM. GarczarczykDeutsches Elektronen-Synchrotron (DESY), 15738 Zeuthen, GermanyM. GaugDepartament de Física, and CERES-IEEC, Universitat Autónoma de Barcelona, 08193 Bellaterra, SpainP. GiammariaNational Institute for Astrophysics (INAF), 00136 Rome, ItalyN. GodinovićCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaD. GubermanInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainD. HadaschRIKEN, 351-0198 Saitama, JapanA. HahnMax-Planck-Institut für Physik, 80805 München, GermanyT. HassanInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainJ. HerreraInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainJohn HoangUnidad de Partículas y Cosmología (UPARCOS), Universidad Complutense, 28040 Madrid, SpainD. HrupecCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaSusumu InoueTokai University, 259-1292 Kanagawa, JapanKazuma IshioMax-Planck-Institut für Physik, 80805 München, GermanyY. IwamuraTokai University, 259-1292 Kanagawa, JapanH. KuboRIKEN, 351-0198 Saitama, JapanJ. KushidaDepartment of Physics, Kyoto University, 606-8502 Kyoto, JapanD. KuveždićCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaA. LamastraNational Institute for Astrophysics (INAF), 00136 Rome, ItalyD. LelasCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaF. LeoneNational Institute for Astrophysics (INAF), 00136 Rome, ItalyE. LindforsFinnish MAGIC Consortium: Tuorla Observatory and Finnish Centre of Astronomy with ESO (FINCA), University of Turku FIN-20014 University of Turku, Finland, Astronomy Division, University of Oulu, 90014, University of Oulu, FinlandS. LombardiNational Institute for Astrophysics (INAF), 00136 Rome, ItalyF. LongoUniversità di Udine, and INFN Trieste, 33100 Udine, ItalyMarcos LópezInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainA. López-OramasInst. de Astrofísica de Canarias, and Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, SpainC. MaggioDepartament de Física, and CERES-IEEC, Universitat Autónoma de Barcelona, 08193 Bellaterra, SpainP. MajumdarSaha Institute of Nuclear Physics, HBNI, 1/AF Bidhannagar, Salt Lake, Sector-1, Kolkata 700064, IndiaM. MakarievInst. for Nucl. Research and Nucl. Energy, Bulgarian Academy of Sciences, 1784 Sofia, BulgariaG. ManevaInst. for Nucl. Research and Nucl. Energy, Bulgarian Academy of Sciences, 1784 Sofia, BulgariaM. ManganaroCroatian MAGIC Consortium: University of Rijeka 51000 Rijeka, University of Split, FESB, 21000 Split, University of Zagreb, FER, 10000 Zagreb, University of Osijek, 31000 Osijek and Rudjer Boskovic Institute, 10000 Zagreb, CroatiaK. MannheimUniversität Würzburg, 97074 Würzburg, GermanyL. MaraschiNational Institute for Astrophysics (INAF), 00136 Rome, ItalyM. MariottiUniversità di Padova and INFN, 35131 Padova, ItalyM. Martı́nezInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainS. MasudaTokai University, 259-1292 Kanagawa, JapanD. MazinMax-Planck-Institut für Physik, 80805 München, GermanyM. MinevInst. for Nucl. Research and Nucl. Energy, Bulgarian Academy of Sciences, 1784 Sofia, BulgariaJ. M. MirandaUniversità di Siena and INFN Pisa, 53100 Siena, ItalyR. MirzoyanMax-Planck-Institut für Physik, 80805 München, GermanyE. MolinaUniversitat de Barcelona, ICCUB, IEEC-UB, 08028 Barcelona, SpainA. MoralejoInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainV. MorenoDepartament de Física, and CERES-IEEC, Universitat Autónoma de Barcelona, 08193 Bellaterra, SpainE. MorettiInstitut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), 08193 Bellaterra (Barcelona), SpainP. Munar-AdroverDepartament de Física, and CERES-IEEC, Universitat Autónoma de Barcelona, 08193 Bellaterra, Spain
2019en
ABI
Abstract
The mechanisms producing fast variability of the γ -ray emission in active galactic nuclei (AGNs) are under debate. The MAGIC telescopes detected a fast, very-high-energy (VHE, E > 100 GeV) γ -ray flare from BL Lacertae on 2015 June 15. The flare had a maximum flux of (1.5 ± 0.3) × 10 −10 photons cm −2 s −1 and halving time of 26 ± 8 min. The MAGIC observations were triggered by a high state in the optical and high-energy (HE, E > 100 MeV) γ -ray bands. In this paper we present the MAGIC VHE γ -ray data together with multi-wavelength data from radio, optical, X-rays, and HE γ rays from 2015 May 1 to July 31. Well-sampled multi-wavelength data allow us to study the variability in detail and compare it to the other epochs when fast, VHE γ -ray flares have been detected from this source. Interestingly, we find that the behaviour in radio, optical, X-rays, and HE γ -rays is very similar to two other observed VHE γ -ray flares. In particular, also during this flare there was an indication of rotation of the optical polarization angle and of activity at the 43 GHz core. These repeating patterns indicate a connection between the three events. We also test modelling of the spectral energy distribution based on constraints from the light curves and VLBA observations, with two different geometrical setups of two-zone inverse Compton models. In addition we model the γ -ray data with the star-jet interaction model. We find that all of the tested emission models are compatible with the fast VHE γ -ray flare, but all have some tension with the multi-wavelength observations.
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