PoS(ICRC2021)834 International th 12–23 July 2021 July 12–23 37 SICS CONFERENCE SICS CONFERENCE Berlin | Germany Berlin Berlin | Germany Cosmic Ray Conference Ray Cosmic ICRC 2021 THE ASTROPARTICLE PHY ICRC 2021 THEASTROPARTICLE PHY https://pos.sissa.it/ observations † NuSTAR ONLINE on behalf of the MAGIC, FACT, 1 ) is one of the brightest and closest BL Lac type objects, and L. Heckmann 1 031 . 0 = I . f 3 D. Paneque ∗ 0, [email protected] observations a clear change of the Compton dominance is detected without a simultaneous GeV) versus X-ray flux correlation is performed, by binning the data into several sub-energy International Cosmic Ray Conference (ICRC 2021) 100 a complete list of the authors can be found at the end of the proceedings Presenter ∗ † th > ETH Zürich, CH-8093 Zürich, Switzerland Max-Planck-Institut für Physik, D-80805 München, Germany E-mail: The blazar Mrk 421 (redshift change in the synchrotron regime, indicatingan "orphan intriguing gamma-ray bright activity". flare Weleptonic at also scenario, investigate VHE this without behaviour a ishighly-energetic best substantial electrons explained flux spanning by increase a the in appearance narrowcorrelation of the range study a of X-rays. also second energies. reveals population Within an of significance Finally, a anti-correlation level our above between multi-wavelength the UV/optical and X-ray bands at a bands. A positively correlated variabilitysubstantially is across the observed, various but bands probed. the correlation Furthermore,NuSTAR during characteristics the change simultaneous MAGIC and making it an ideal targetobserving to campaign in probe 2017, during blazar which the physics. intra-band correlationand patterns We complex show report some behaviours. disparity on Observations an fromtemporal extensive several coverage from multi-wavelength instruments radio to are TeV energies. used In to particular,organised achieve four multi-hour an simultaneously optimal with MAGICsegments allow of the to two spectral obtain components. a A detailed precise investigation of measurement the very-high-energy (VHE; of the falling Copyright owned by the author(s) under the terms of the Creative Commons 0 1 © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). 37 July 12th – 23rd, 2021 Online – Berlin, Germany Fermi-LAT Collaborations and multi-wavelength collaborators A. Arbet-Engels, Unveiling the complex correlation patterns in Mrk 421 PoS(ICRC2021)834 031 . Hz to 0 = 16 satellite, I 10 ∼ that took place A. Arbet-Engels GeV) gamma rays. 100 NuSTAR > -XRT data, we investigate the VHE versus Neil Gehrels Swift Observatory (Swift) Swift 2 observations, without any simultaneous change of and NuSTAR NuSTAR -LAT energy bands did not show any significant enhancement. keV remained close to the typical level of Mrk 421. In addition, 1 ≈ Fermi -LAT instrument. The gamma-ray measurements were complemented during the . Mrk 421 is the only BL Lac where such a behaviour was observed so f 3 day), from radio to very-high-energy (VHE; 3 1 Fermi ≈ . -UVOT and telescopes from the GASP-WEBT network. Finally, OVRO, Medicina Swift Hz. Furthermore, the UV/optical and X-ray fluxes exhibit anti-correlated variability at a 18 The temporal evolution of the synchrotron emission is also characterised in detail by exploiting During the first half of the campaign, the source showed several days of high flux activities in Using the simultaneous MAGIC, Mrk 421 is a high-frequency peaked BL Lac (HBL) type object located at a redshift 10 & the dense temporal coverage in thefrequency optical, shifted UV by about and two X-rays. orders The of location magnitude of throughout the the synchrotron campaign, peak from X-ray correlation throughout the campaignpositively by correlated binning variability the data is into observed,characteristics depend several as substantially sub-energy on already the bands. energy reported bands A probed.linear for to The Mrk a correlation 421 more-than-cubic ranges from relation. [3]. a Furthermore, sub- dominance we by However, report a the significant factor variability inthe the synchrotron Compton emission. Based on anmay SSC be model, explained by we an show emitting that zone this thatloss "orphan is in adiabatically gamma-ray expanding activity" the over time, total without number a of significant electrons. the VHE band. The fluxis above more 200 GeV than was twice regularly the higher typicaldetected than flux on that of 2017 of Mrk February the 421 4. Crab [2].about On Nebula, 7 that In which day, times particular, FACT that measurements a of revealed short a the andX-ray maximum band Crab bright VHE and Nebula. VHE flux the However, flare emission of only at was a moderate flux increase was detected in the The temporal evolution of the broadbandof emission precision can compared thus be to characterisedblazar other with jet BL a physics. higher Lac degree typewavelength Between campaign objects, on December Mrk making 2016 421. Mrk andexcellent Data 421 coverage June from in an many 2017, energy instruments ideal we and were targetby collected organised time. the to in an MAGIC order study and At extensive to FACT very telescopes. multi- obtain highmeasurements In from energies, the the high-energy the band observations (0.2-2 were GeVby & an carried impressive 2-300 X-ray GeV), coverage out using we data used from the as well as foursimultaneously deep with exposures MAGIC from observations. themade In by sensitive the hard UV X-ray andand satellite optical Metsähovi observations bands, were performed the to observations characterise were the behaviour in the radio band. the flux in the optical/UV and By studying the evolution ofbehaviour the is broadband difficult spectral to energymodel. reproduce distribution Instead, within (SED), the we a VHE find flare standard couldwith that one-zone be a this explained synchrotron narrow by distribution self-Compton the of emergence (SSC) highlyblob of energetic a would electrons. small combine emitting The with zone radiation that filled fromdominate from this the a compact emission larger emitting emitting only zone inSEDs. responsible the for hard the X-ray quiescent and state VHE and regimes, thus reproducing the observed significance level above The complex correlation patterns in Mrk 421 [1]. Its proximity andtime flux scales brightness (within allow us to achieve a significant signal detection on short PoS(ICRC2021)834 A. Arbet-Engels 3 LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that 576, A126. 2021, arXiv, arXiv:2106.05516 Detailed information about analysis and results have been published in [4]. The MAGIC Collaboration would like to thank the Instituto de Astrofísica de Canarias for the excellent working con- Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Fermi [1] de Vaucouleurs G., de Vaucouleurs A., Corwin H.[2] G., Buta R.Acciari V. J., A., Paturel Arlen G., T., Fouque Aune P., T., 1991, Benbow rc3..book W.,[3] Bird R., BouvierAleksić A., J., Ansoldi Bradbury S., S. Antonelli M., L. et A., Antoranz al., P., 2014, Babic APh, A., Bangale 54, P., 1. Barres de Almeida[4] U., et al.,MAGIC 2015, Collaboration, A&A, Acciari V. A., Ansoldi S., Antonelli L. A., Arbet Engels A., Artero M., Asano K., et al., References Acknowledgments ditions at the Observatorio del Roque deand los HGF; Muchachos the in Italian La INFN Palma. andcia The INAF; e financial the support Innovacion (MICINN) Swiss of the (FPA2017-87859-P, National FPA2017-85668-P, FPA2017-82729-C6-5-R, German Fund FPA2017-90566-REDC, PID2019-104114RB-C31, BMBF, SNF; MPG the PID2019-104114RB-C32, ERDF under PID2019-105510GB-C31,PID2019-107847RB-C41, the107847RB-C42, Spanish PID2019- PID2019-107847RB-C44, Ministerio de PID2019-107988GB-C22); Cien- theJapanese Indian ICRR, Department the of University of Atomic Tokyo,RI Energy; JSPS, and Roadmap the MEXT; Project the DO1-268/16.12.2019 Bulgarian and MinistryThis of the work Education Academy was and of also Science, supported Finland National and by grant CEX2019-000920-S, the nr. and Spanish "María Centro 320045 de de isMDM-2015-0509-18-2 Maeztu” Excelencia and gratefully the CEX2019-000918-M, “Severo acknowledged. "la Ochoa” the Caixa" SEV-2016-0588, Foundation Unidad (fellowship SEV-2017-0709 LCF/BQ/PI18/11630012) deof and Excelencia the by Generalitat the “María CERCA de de program Catalunya; by Maeztu” theof Croatian Rijeka Science Foundation Project (HrZZ) Project 13.12.1.3.02; IP-2016-06-9782National and by Research the Centre the University grant DFG UMO-2016/22/M/ST9/00382; Collaborative andThe by Research the FACT Centers Collaboration Brazilian MCTIC, SFB823/C4 acknowledges CNPq the and and27.12-1 important SFB876/C3; FAPERJ. as contributions well the from as Polish the ETH fundingphysik) Zurich by and grants the ETH-10.08-2 Swiss HAP SNF and (Helmoltz andsupported ETH- the Alliance by German Deutsche for BMBF Forschungsgemeinschaft (Verbundforschung Astroparticle (DFG) Astro-Information within und Physics) by Astroteilchen- the are Resource-Constrained Collaborative Analysis", Research gratefully project Center acknowledged.E. C3. SFB Lorenz, 876 We "Providing are Part D. thankful Renker of forCanarias and this the for G. very work allowing Viertel valuable us is contributions duringMax-Planck-Institut to from the für operate Physik early for the phase providing telescope of uscollaboration at with the for the the their project. mount support. Observatorio of We del theThe thank former Roque HEGRA the de CT3 Instituto los telescope, de Muchachos andhave Astrofísica in the supported MAGIC de both La the Palma, development and the National the Aeronautics operation and of the Space LAT Administration asà and well l’Energie the as scientific Department Atomique data and of analysis. Energy theet These in Centre de include the Physique the National United des de States, Particules laItaly, the in the Recherche Commissariat France, Ministry Scientifique of the / Education, Agenzia Institut Culture,Organization Spaziale Sports, National (KEK) Italiana and Science de and Japan and Physique the Aerospace Technology Nucléaire Exploration (MEXT), Istitutothe Agency High Nazionale Swedish (JAXA) Energy Research di in Accelerator Council Japan, Fisica Research and and Nucleare the the in Swedish K. National A. Space Wallenberg Board Foundation, in Sweden. Nazionale di Astrofisica in Italy and theDOE Centre National Contract d’Études DE-AC02-76SF00515. Spatiales in France. This work performed in part under The complex correlation patterns in Mrk 421 far and it indicates variations in the efficiency of the particle cooling and acceleration mechanisms. PoS(ICRC2021)834 , , , , , , , , , , , , , , , , , , , , 2 1 3 6 3 3 9 5 2 5 9 1 8 1 32 22 11 40 12 17 24 25 ETH 4 now at , U. Bar- 9 42 , T. Saito , L. Nava also at Port , S. Paiano , L. Jouvin , G. Vanzo 28 , T. Miener 35 1 , Ž. Bošnjak , J. Herrera 44 25 15 49 , B. De Lotto , F. Tavecchio , N. Giglietto 16 15 , , E. Colombo , E. Lindfors 6 2 5 , B. Machado de , T. Yamamoto Croatian MAGIC 3 11 Croatian MAGIC 26 , M. Bernardos , M. V. Fonseca , K. Mannheim , D. Sobczynska 7 IPARCOS Institute 22 13 University of Lodz, now at Laboratoire 8 37 14 23 37 9 12 , A. Baquero A. Arbet-Engels 49 8 , P. G. Prada Moroni Saha Institute of Nuclear 15 , N. Sahakyan , E. Do Souto Espiñeira 33 , T. Nakamori , M. Gaug , G. Bonnoli , D. Miceli , F. Leone 5 , R. Takeishi 7 17 22 28 Centro de Investigaciones En- 6 23 29 , J. Otero-Santos , L. Heckmann , J. Jormanainen , S. M. Colak Max-Planck-Institut für Physik, , A. Fattorini 31 , I. Šnidarić 8 , A. Babić 20 , A. De Angelis 15 20 , S. Loporchio 7 45 3 15 12 , E. Bernardini , C. Wunderlich , 1 Università di Siena and INFN Pisa, , M. Pihet , M. Manganaro 13 15 25 50 , J. van Scherpenberg 13 , Centro Brasileiro de Pesquisas Físicas 34 2 26 , E. Moretti , T. Oka , D. Lelas 10 6 3 26 , S. Cikota , S. Gasparyan , A. Hahn , F. Dazzi , D. Baack , M. Takahashi , S. Mićanović , L. Di Venere , J. Sitarek , H. Bökenkamp 6 6 , M. Will , A. Rugliancich 7 19 14 43 5 now at University of Innsbruck 6 37 3 , 21 15 , L. Bellizzi 17 43 , M. Persic , S. Ubach 12 9 , G. Maneva Finnish MAGIC Group: Finnish Centre for Astron- 3 , Y. Ohtani Inst. for Nucl. Research and Nucl. Energy, Bulgarian 11 25 , A. López-Oramas 31 , V. Moreno , I. Vovk 34 , I. Jiménez Martínez 9 , K. Asano 9 , T. Surić , A. Lamastra 6 5 , C. Righi Japanese MAGIC Group: Department of Physics, Konan 39 , O. Blanch now at Department of Astronomy, University of California 5 , V. Fallah Ramazani , S. Mender 27 32 4 now at Ruhr-Universität Bochum, Fakultät für Physik und , D. Hadasch 7 , P. Peñil 40 46 13 , P. Da Vela , T. Schweizer 15 , F. Di Pierro INFN MAGIC Group: INFN Sezione di Torino and Università 23 45 3 7 , M. Garczarczyk , A. Tutone 21 , A. Chilingarian 1 21 , W. Bednarek Armenian MAGIC Group: ICRANet-Armenia at NAS RA, 0019 13 15 , S. Nozaki 1 Departament de Física, and CERES-IEEC, Universitat Autònoma , J. Rico 6 , V. Vitale , Y. Suda 4 , M. Artero 6 28 18 4 21 , M. Mallamaci , A. Biland 26 , Y. Iwamura 3 Croatian MAGIC Group: University of Rijeka, Department of Physics, , J. Kushida National Institute for Astrophysics (INAF), I-00136 Rome, Italy 34 12 , D. Morcuende , D. Green INFN MAGIC Group: INFN Sezione di Perugia, I-06123 Perugia, Italy Universitat de Barcelona, ICCUB, IEEC-UB, E-08028 Barcelona, Spain 3 , V. D’Elia , D. Elsaesser 31 5 23 3 , M. López-Moya , L. Pavletić , K. Schmidt , S. Menchiari 42 11 , Y. Chai 38 11 Università di Padova and INFN, I-35131 Padova, Italy , 18 18 , K. Noda 24 , S. Truzzi 15 , D. Depaoli , 18 15 11 6 , M. Ribó 32 38 20 , M. Strzys 7 15 , K. Ishio Japanese MAGIC Group: Department of Physics, Yamagata University, Yamagata Croatian MAGIC Group: Josip Juraj Strossmayer University of Osijek, Department 6 , H. Kubo , R. J. García López , C. F. Vigorito Japanese MAGIC Group: Institute for Cosmic Ray Research (ICRR), The University 30 35 6 , C. Bigongiari , M. Doro INFN MAGIC Group: INFN Sezione di Bari and Dipartimento Interateneo di Fisica , M. Makariev 27 34 6 Technische Universität Dortmund, D-44221 Dortmund, Germany , A. Arbet-Engels , A. Moralejo 14 , J. G. Green 24 , J. Becerra González also at International Center for Relativistic Astrophysics (ICRA), Rome, Italy 3 33 7 , L. Tosti Japanese MAGIC Group: Physics Program, Graduate School of Advanced Science and 22 18 , D. Mazin 29 6 11 , , M. Cerruti 41 5 , J. M. Paredes , W. Rhode , B. Schleicher , D. Strom , G. D’Amico 27 , R. López-Coto 15 15 3 , T. Inada 3 13 , K. Nishijima 29 Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology 30 47 15 , 25 5 Japanese MAGIC Group: Department of Physics, Kyoto University, 606-8502 Kyoto, Japan 2 31 also at Dipartimento di Fisica, Università di Trieste, I-34127 Trieste, Italy , D. Dorner , V. Verguilov , Y. Fukazawa Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008, Granada, Spain , Y. Kobayashi 2 , E. Molina 6 5 , C. Delgado Mendez 13 , I. Batković 47 , P. Majumdar 15 16 9 , I. Puljak 44 , S. Covino , L. A. Antonelli 5 , 26 , R. Paoletti , M. Martínez , N. Godinović 5 , M. Teshima , W. Bhattacharyya 20 41 , F. G. Saturni , M. Hütten , F. Longo , G. Ceribella 15 11 , , J. Strišković 12 , K. Nilsson 3 2 Universität Würzburg, D-97074 Würzburg, Germany 3 23 15 5 14 30 17 Deutsches Elektronen-Synchrotron (DESY), D-15738 Zeuthen, Germany 24 Croatian MAGIC Group: University of Split, Faculty of Electrical Engineering, Mechanical Engineering and , A. Donini , S. Fukami 14 , S. Ventura 23 Finnish MAGIC Group: Astronomy Research Unit, University of Oulu, FI-90014 Oulu, Finland 29 1 15 , J. A. Barrio 36 , D. Kerszberg , C. Maggio , R. Mirzoyan , J. Cortina 1 10 , J. Delgado , C. Nigro 9 , T. Terzić 10 13 , P. Gliwny , S. Ansoldi , D. Paneque , C. Priyadarshi , M. Mariotti , R. Carosi 44 36 1 2 , D. Hrupec 34 29 , 22 , A. Stamerra 3 , S. Lombardi 5 , K. Satalecka 11 11 46 7 6 11 , J. Besenrieder , , C. Fruck 9 15 26 Università di Pisa and INFN Pisa, I-56126 Pisa, Italy Armenian MAGIC Group: A. Alikhanyan National Science Laboratory, 0036 Yerevan, Armenia INFN MAGIC Group: INFN Roma Tor Vergata, I-00133 Roma, Italy Instituto de Astrofísica de Canarias and Dpto. de Astrofísica, Universidad de La Laguna, E-38200, La Laguna, Tenerife, Spain A. Spolon S. Sakurai E. Prandini M. Palatiello V. Neustroev J. M. Miranda M. Karjalainen F. Giordano J. Hoang L. Maraschi M. Delfino D. Dominis Prester L. Font L. Linhoff A. Berti G. Busetto J. L. Contreras Oliveira Fraga The complex correlation patterns in Mrk 421 Full Authors List: MAGIC Collaboration: V. A. Acciari res de Almeida M. Vazquez Acosta 19 ergéticas, Medioambientales y Tecnológicas, E-28040 Madrid,degli Spain Studi di Torino, I-10125dell’Università e Torino, del Italy Politecnico di Bari, I-70125 Bari, Italy (BIST), E-08193 Bellaterra (Barcelona), Spain of Tokyo, Kashiwa, 277-8582 Chiba, Japan 17 51000 Rijeka, Croatia P. Temnikov and D. Zarić 1 Università di Udine and INFNZürich, Trieste, CH-8093 I-33100 Zürich, Udine, Switzerland Italy Group: University of Zagreb,and Faculty EMFTEL of Department, Electrical Engineering Universidad(CBPF), Complutense and 22290-180 Computing de URCA, Rio (FER), Madrid, de 10000 Janeiro E-28040Faculty (RJ), Zagreb, Madrid, of Brazil Croatia Physics Spain and Applied Informatics,I-53100 Department Siena, of Italy Astrophysics, 90-236 Lodz,D-80805 Poland München, Germany omy with ESO, University ofde Turku, Barcelona, FI-20014 E-08193 Turku, Bellaterra, Finland Engineering, Spain Hiroshima University, 739-8526 Hiroshima, Japan Yerevan, Armenia d’Informació Científica (PIC), E-08193 Bellaterra (Barcelona), Spain Naval Architecture (FESB), 21000 Split, Croatia of Physics, 31000 Osijek, Croatia Astronomie, Astronomisches Institut (AIRUB), 44801 Bochum, Germany Japanese MAGIC Group: Department of Physics, Tokai University, Hiratsuka, 259-1292 Kanagawa, Japan University, Kobe, Hyogo 658-8501, Japan Department for Physics and Technology, University of Bergen, NO-5020, Norway Berkeley, Berkeley CA 94720 39 Physics, HBNI, 1/AF Bidhannagar, Salt Lake, Sector-1,Academy Kolkata of 700064, Sciences, India BG-1784 Sofia,990-8560, Bulgaria Japan Group: Ruđer Bošković Institute, 10000 Zagreb, Croatia PoS(ICRC2021)834 , 11 , , , , , , , , , , , 7 10 1 2 2 22 30 34 24 27 23 14 21 35 38 , , 33 23 Graduate 27 , A. Pandey , M. Samal , W. Rhode , J. Kania , N. Marchili 4 1 14 27 , E. Ovcharov Aalto University , D. Elsaesser , T. S. Grishina 33 , A. Lähteenmäki 4 18 10 9 , 25 7 , R. G. Chanishvili A. Arbet-Engels 39 , , J. A. Acosta-Pulido Foundation for Research , A. A. Nikiforova 38 TU Dortmund, Experimen- 33 23 16 W.W. Hansen Experimental 2 , M. Feige , C. Leto , A. Paravac , A. C. Gupta 6 , W. P. Chen , M. Giroletti 8 2 , 28 23 7 31 29 , A. Strigachev INAF—Osservatorio Astrofisico di , G. A. Borman 18 , L. Eisenberger Institute for Astrophysical Research, 4 24 Department of Physics, University of 28 , , C. Lorey 31 23 17 also at INAF Trieste and Dept. of Physics 34 Zentrum für Astronomie der Universität , INAF - Osservatorio Astronomico di Roma, 50 33 , M. Noethe 39 1 8 , M. Spencer , F. Verrecchia , C. M. Raiteri , M. G. Nikolashvili , D. A. Morozova , R. Bachev 8 29 , Z. R. Weaver , 28 41 7 Aalto University Department of Electronics and 23 20 , , D. Dorner 31 2 39 , O. A. Merkulova , 11 38 Astrophysics Science Division, NASA Goddard Space INAF, TNG Fundaci ón Galileo Galilei, E-38712 La 23 2 Samtskhe-Javakheti State University, Rustaveli Str. 113, , D. Neise , V. M. Larionov 37 Crimean Astrophysical Observatory RAS, P/O Nauchny, 1 , M. Perri , L. Schneider 40 6 22 , M. Villata 25 , J. Buss , M. D. Joner 34 , 11 , A. Marchini , ,0 38 33 1 19 10 Sobolev Astronomical Institute, St. Petersburg State University, St. Department of Physics, University of Maryland, Baltimore County, , A. P. Marscher , L. V. Larionova 5 Astronomy Department, Universidad de Concepción, Casilla 160-C, 3 32 Astronomical Institute, St. Petersburg State University, St. Petersburg, , O. Vince 23 32 University of Geneva, Department of Astronomy, Chemin dÉcogia 16, , , A. A. Vasilyev 12 22 , A. Mitchell 23 3 , O. M. Kurtanidze 4 31 23 40 , T. Bretz , G. M. Madejski , 1 5 , L. A. Sigua , 39 , S. Ibryamov 4 , , R. J. C. Vera 38 18 38 13 , A. Scherbantin , Yale Center for Astronomy & Astrophysics, 52 Hillhouse Avenue, New Haven, CT 10 34 4 , 33 Italian Space Agency, ASI, via del Politecnico snc, 00133 Roma, Italy , S. G. Jorstad , A. Biland , G. Damljanovic , E. G. Larionova 9 , K. Mannheim 3 30 4 Department of Physics and Astronomy, Brigham YoungUniversity, Provo, UT 84602 USA 21 23 , Y. V. Troitskaya , E. Semkov , M. Baloković 29 23 3 , , E. Järvelä 17 , 3 2 Department of Astronomy, Faculty of Physics, University of Sofia, BG-1164 Sofia, Bulgaria 12 16 , , G. N. Kimeridze Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, , S. O. Kurtanidze 21 10 38 , D. Reinhart 37 18 , , M. Balbo 36 34 2 , , A. C. Sadun , E. Zaharieva University of Würzburg, Institute for Theoretical Physics and Astrophysics, Emil-Fischer-Str. 31, 97074 , A. Kalenski 33 , A.Y.Lien , R. Walter 4 4 29 21 University of Siena, Department of Physical Sciences, Earth and Environment, Astronomical Observatory, Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital - 263 001, India 3 43 University of Würzburg, Institute for Theoretical Physics and Astrophysics, Emil-Fischer-Str. 31, 97074 , C. Casadio , I. S. Troitskiy 20 14 Instituto de Astrofísica de Canarias and Dpto. de Astrofísica, Universidad de La Laguna, E-38200, La Laguna, also at RWTH Aachen University 15 European Space Agency, European Space Astronomy Centre, C/ Bajo el Castillo s/n, 28692 Villanueva de la , E. N. Kopatskaya Hans-Haffner-Sternwarte, Naturwissenschaftliches Labor für Schüler; Friedrich-Koenig-Gymnasium, D-97082 34 26 44 0 35 , 23 13 Special Astrophysical Observatory, Russian Academy of Sciences, 369167, Nizhnii Arkhyz, Russia 33 EPT Observatories, Tijarafe, E-38780 La Palma, Spain Pulkovo Observatory, St.-Petersburg, 196140, Russia 24 , D. Baack , R. Z. Ivanidze , , D. Carosati Department of Physics and Astronomy, Faculty of Natural Sciences, University of Shumen, 115, Universitetska Str., Abastumani Observatory, Mt. Kanobili, 0301 Abastumani, Georgia 1 , V. Ramakrishnan , R. Iotov 38 26 , L. Kunkel 23 24 36 , D. Horan 28 19 1 , V. Sliusar 1 Department of Physics, Yale University, P.O. Box 2018120, New Haven, CT 06520, USA 38 10 4 , A. Valcheva 34 5 , I. Agudo , , N. Rizzi , J. W. Moody 21 33 15 42 27 Instituto de Astrofísica de Andalucía - CSIC, Glorieta de la Astronomía s/n, E-18008, Granada, Spain INAF - Istituto di Radioastronomia, Via Gobetti 101, I-40129 Bologna, Italy ETH Zurich, Institute for Particle Physics and Astrophysics, Otto-Stern-Weg 5, 8093 Zurich, Switzerland Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA Palma, Spain Via Roma 56, I-53100 Siena, Italy Würzburg, Germany S. Righini 1 1000 Hilltop Circle, Baltimore, MD 21250,06511, USA USA Physics Laboratory, Kavli Institute for Particle Astrophysics andSpace Science Cosmology, Data Department Center of (SSDC) Physics - and ASI, SLAC viavia National del di Accelerator Politecnico, Frascati 33,I-00040 s.n.c., Monteporzio, I-00133, Italy Roma, Italy Metsähovi Radio Observatory, Metsähovintie 114,Nanoengineering, FIN-02540 P.O. Kylmälä, Box Finland 15500, FIN-00076 Aalto,Concepción, Finland Chile Cañada, Madrid, Spain 15 and Technology - Hellas, IESL &Crete, Institute 71003, of Heraklion, Astrophysics, Greece Voutes, 7110 Heraklion,Sofia, Bulgaria Greece 9712 Shumen, Bulgaria Astronomical Observatory, Volgina 7, 11060 Belgrade, Serbia Department of Physics, University of Colorado Denver, Denver, Colorado, COBoston 80217-3364, University, USA 725 Commonwealth Ave, Boston, MA 02215 Petersburg, Russia Würzburg, Germany Tenerife, Spain Heidelberg, Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany 198504, Russia , M. Kopp M. I. Carnerero R. A. Chigladze 298409, Russia Institute of Astronomy, National Central University, 300 ZhongdaTorino, I-10025 Road, Pino Zhongli Torinese (TO), 32001, Italy Taiwan The complex correlation patterns in Mrk 421 d’Annecy de Physique des Particules (LAPP), CNRS-IN2P3, 74941and Annecy Astronomy, University Cedex, of France Bologna, Bologna, Italy FACT Collaboration: A. Arbet-Engels S. S. Savchenko H. C. Lin D. Hildebrand V. A. Hagen-Thorn A. Fuentes V. Bozhilov Other groups and collaborations: F. D’Ammando B. Schleicher tal Physics 5, Otto-Hahn-Str. 4a,1290 44227 Versoix, Dortmund, Switzerland Germany Würzburg, Germany M. Tornikoski 1 PoS(ICRC2021)834 INAF Istituto di 42 A. Arbet-Engels Laboratoire Leprince-Ringuet, École 43 6 Osservatorio Astronomico Sirio, I-70013 Castellana Grotte, Italy 44 Engelhardt Astronomical Observatory, Kazan Federal University, Tatarstan, Russia 41 Radioastronomia, Stazione di Medicina, via Fiorentina 3513,polytechnique, CNRS/IN2P3, I-40059 F-91128 Villafontana Palaiseau, (BO), France Italy The complex correlation patterns in Mrk 421 0080 Akhaltsikhe, Georgia