Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017

V.A. Acciari , S. Ansoldi , L.A. Antonelli , A. Arbet Engels , M. Artero , K. Asano , A. Babić , A. Baquero , U. Barres de Almeida , J.A. Barrio , I. Batković , J. Becerra González , W. Bednarek , L. Bellizzi , E. Bernardini , M. Bernardos , A. Berti , J. Besenrieder , W. Bhattacharyya , C. Bigongiari , O. Blanch , Z. Bošnjak , G. Busetto , R. Carosi , G. Ceribella , M. Cerruti , Y. Chai , A. Chilingarian , S. Cikota , S.M. Colak , E. Colombo , J.L. Contreras , J. Cortina , S. Covino , G. d'Amico , V. d'Elia , P. da Vela , F. Dazzi , A. de Angelis , B. de Lotto , M. Delfino , J. Delgado , C. Delgado Mendez , D. Depaoli , F. Di Pierro , L. Di Venere , E. Do Souto Espiñeira , D. Dominis Prester , A. Donini , M. Doro , V. Fallah Ramazani , A. Fattorini , G. Ferrara , M.V. Fonseca , L. Font , C. Fruck , S. Fukami , R.J. García López , M. Garczarczyk , S. Gasparyan , M. Gaug , N. Giglietto , F. Giordano , P. Gliwny , N. Godinović , J.G. Green , D. Green , D. Hadasch , A. Hahn , L. Heckmann , J. Herrera , J. Hoang , D. Hrupec , M. Hütten , T. Inada , S. Inoue , K. Ishio , Y. Iwamura , I. Jiménez , J. Jormanainen , L. Jouvin , Y. Kajiwara , M. Karjalainen , D. Kerszberg , Y. Kobayashi , H. Kubo , J. Kushida , A. Lamastra , D. Lelas , F. Leone , E. Lindfors , S. Lombardi , F. Longo , R. López-Coto , M. López-Moya , A. López-Oramas , S. Loporchio , B. Machado de Oliveira Fraga , C. Maggio , P. Majumdar , M. Makariev , M. Mallamaci , G. Maneva , M. Manganaro , L. Maraschi , M. Mariotti , M. Martínez , D. Mazin , S. Menchiari , S. Mender , S. Mićanović , D. Miceli , T. Miener , M. Minev , J.M. Miranda , R. Mirzoyan , E. Molina , A. Moralejo , D. Morcuende , V. Moreno , E. Moretti , V. Neustroev , C. Nigro , K. Nilsson , K. Nishijima , K. Noda , S. Nozaki , Y. Ohtani , T. Oka , J. Otero-Santos , S. Paiano , M. Palatiello , D. Paneque , R. Paoletti , J.M. Paredes , L. Pavletić , P. Peñil , C. Perennes , M. Persic , P.G. Prada Moroni , E. Prandini , C. Priyadarshi , I. Puljak , M. Ribó , J. Rico , C. Righi , A. Rugliancich , L. Saha , N. Sahakyan , T. Saito , S. Sakurai , K. Satalecka , F.G. Saturni , K. Schmidt , T. Schweizer , J. Sitarek , I. Šnidarić , D. Sobczynska , A. Spolon , A. Stamerra , D. Strom , M. Strzys , Y. Suda , T. Surić , M. Takahashi , F. Tavecchio , P. Temnikov , T. Terzić , M. Teshima , L. Tosti , S. Truzzi , A. Tutone , S. Ubach , J. van Scherpenberg , G. Vanzo , M. Vazquez Acosta , S. Ventura , V. Verguilov , C.F. Vigorito , V. Vitale , I. Vovk , M. Will , C. Wunderlich , D. Zarić , D. Baack , M. Balbo , N. Biederbeck , A. Biland , T. Bretz , J. Buss , D. Dorner , L. Eisenberger , D. Elsaesser , D. Hildebrand , R. Iotov , K. Mannheim , D. Neise , M. Noethe , A. Paravac , W. Rhode , B. Schleicher , V. Sliusar , R. Walter , F. d'Ammando , D. Horan (1) , A.Y. Lien , M. Baloković , G.M. Madejski , M. Perri , F. Verrecchia , C. Leto , A. Lähteenmäki , M. Tornikoski , V. Ramakrishnan , E. Järvelä , R.J.C. Vera , M. Villata , C.M. Raiteri , A.C. Gupta , A. Pandey , A. Fuentes , I. Agudo , C. Casadio , E. Semkov , S. Ibryamov , A. Marchini , R. Bachev , A. Strigachev , E. Ovcharov , V. Bozhilov , A. Valcheva , E. Zaharieva , G. Damljanovic , O. Vince , V.M. Larionov , G.A. Borman , T.S. Grishina , V.A. Hagen-Thorn , E.N. Kopatskaya , E.G. Larionova , L.V. Larionova , D.A. Morozova , A.A. Nikiforova , S.S. Savchenko , I.S. Troitskiy , Y.V. Troitskaya , A.A. Vasilyev , O.A. Merkulova , W.P. Chen , M. Samal , H.C. Lin , J.W. Moody , A.C. Sadun , S.G. Jorstad , A.P. Marscher , Z.R. Weaver , M. Feige , J. Kania , M. Kopp , L. Kunkel , D. Reinhart , A. Scherbantin , L. Schneider , C. Lorey , J.A. Acosta-Pulido , M.I. Carnerero , D. Carosati , S.O. Kurtanidze , O.M. Kurtanidze , M.G. Nikolashvili , R.G. Chanishvili , R.A. Chigladze , R.Z. Ivanidze , G.N. Kimeridze , L.A. Sigua , M.D. Joner , M. Spencer , M. Giroletti , N. Marchili , S. Righini , N. Rizzi , G. Bonnoli

1 LLR - Laboratoire Leprince-Ringuet

Aims. We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations.Methods. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina, and Metsähovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components.Results. The very-high-energy (VHE; E >  100 GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow different patterns, partly due to substantial changes in the Compton dominance for a few days without a simultaneous increase in the X-ray flux (i.e., orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including NuSTAR observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. The peak frequency of the synchrotron bump varies by two orders of magnitude throughout the campaign. Our multi-band correlation study also hints at an anti-correlation between UV-optical and X-ray at a significance higher than 3σ. A VHE flare observed on MJD 57788 (2017 February 4) shows gamma-ray variability on multi-hour timescales, with a factor ten increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario. We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors, from γ′min=2×104 to γ′max=6×105.Key words: galaxies: active / BL Lacertae objects: individual: Mrk 421 / radiation mechanisms: non-thermal⋆ Light curves and spectral energy distributions data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/655/A89⋆⋆ Corresponding authors: A. Arbet Engels and D. Paneque; e-mail: [e-mail].⋆⋆⋆ Also member of the MAGIC Collaboration.⋆⋆⋆⋆ Also member of the FACT Collaboration.

Mots clés: galaxies: active; BL Lacertae objects: individual: Mrk 421; radiation mechanisms: non-thermal; flux: correlation; X-ray: flux; model: leptonic; gamma ray: VHE; spectral; MAGIC; ultraviolet; TeV; electron; Lorentz; optical; blazar; GLAST; GeV

Domaines: Astrophysique [astro-ph]

V.A. Acciari, S. Ansoldi, L.A. Antonelli, A. Arbet Engels, M. Artero, et al.. Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017. Astronomy and Astrophysics - A&A, 2021, 655, pp.A89. ⟨10.1051/0004-6361/202141004⟩. ⟨hal-03268879⟩