MAGIC CollaborationAcciari, V. A.V. A.AcciariAnsoldi, S.S.AnsoldiANTONELLI, Lucio AngeloLucio AngeloANTONELLIArbet Engels, A.A.Arbet EngelsArtero, M.M.ArteroAsano, K.K.AsanoBabić, A.A.BabićBaquero, A.A.BaqueroBarres de Almeida, U.U.Barres de AlmeidaBarrio, J. A.J. A.BarrioMajumdar, P.P.MajumdarMakariev, M.M.MakarievMallamaci, M.M.MallamaciManeva, G.G.ManevaManganaro, M.M.ManganaroMaraschi, L.L.MaraschiMariotti, M.M.MariottiMartínez, M.M.MartínezMazin, D.D.MazinMenchiari, S.S.MenchiariBatković, I.I.BatkovićMender, S.S.MenderMićanović, S.S.MićanovićMiceli, D.D.MiceliMiener, T.T.MienerMinev, M.M.MinevMiranda, J. M.J. M.MirandaMirzoyan, R.R.MirzoyanMolina, E.E.MolinaMoralejo, A.A.MoralejoMorcuende, D.D.MorcuendeBecerra González, J.J.Becerra GonzálezMoreno, V.V.MorenoMoretti, E.E.MorettiNeustroev, V.V.NeustroevNigro, C.C.NigroNilsson, K.K.NilssonNishijima, K.K.NishijimaNoda, K.K.NodaNozaki, S.S.NozakiOhtani, Y.Y.OhtaniOka, T.T.OkaBednarek, W.W.BednarekOtero-Santos, J.J.Otero-SantosPAIANO, SimonaSimonaPAIANOPalatiello, M.M.PalatielloPaneque, D.D.PanequePaoletti, R.R.PaolettiParedes, J. M.J. M.ParedesPavletić, L.L.PavletićPeñil, P.P.PeñilPerennes, C.C.PerennesPERSIC, MassimoMassimoPERSICBellizzi, L.L.BellizziPrada Moroni, P. G.P. G.Prada MoroniPRANDINI, ELISAELISAPRANDINIPriyadarshi, C.C.PriyadarshiPuljak, I.I.PuljakRibó, M.M.RibóRico, J.J.RicoRIGHI, ChiaraChiaraRIGHIRugliancich, A.A.RugliancichSaha, L.L.SahaSahakyan, N.N.SahakyanBernardini, E.E.BernardiniSaito, T.T.SaitoSakurai, S.S.SakuraiSatalecka, K.K.SataleckaSATURNI, Francesco GabrieleFrancesco GabrieleSATURNISchmidt, K.K.SchmidtSchweizer, T.T.SchweizerSitarek, J.J.SitarekŠnidarić, I.I.ŠnidarićSobczynska, D.D.SobczynskaSpolon, A.A.SpolonBernardos, M.M.BernardosSTAMERRA, AntonioAntonioSTAMERRAStrom, D.D.StromStrzys, M.M.StrzysSuda, Y.Y.SudaSurić, T.T.SurićTakahashi, M.M.TakahashiTAVECCHIO, FabrizioFabrizioTAVECCHIOTemnikov, P.P.TemnikovTerzić, T.T.TerzićTeshima, M.M.TeshimaBerti, A.A.BertiTosti, L.L.TostiTruzzi, S.S.TruzziTutone, A.A.TutoneUbach, S.S.Ubachvan Scherpenberg, J.J.van ScherpenbergVanzo, G.G.VanzoVazquez Acosta, M.M.Vazquez AcostaVentura, S.S.VenturaVerguilov, V.V.VerguilovVigorito, C. F.C. F.VigoritoBesenrieder, J.J.BesenriederVitale, V.V.VitaleVovk, I.I.VovkWill, M.M.WillWunderlich, C.C.WunderlichZarić, D.D.ZarićFACT CollaborationBaack, D.D.BaackBalbo, M.M.BalboBiederbeck, N.N.BiederbeckBiland, A.A.BilandBhattacharyya, W.W.BhattacharyyaBretz, T.T.BretzBuss, J.J.BussDorner, D.D.DornerEisenberger, L.L.EisenbergerElsaesser, D.D.ElsaesserHildebrand, D.D.HildebrandIotov, R.R.IotovMannheim, K.K.MannheimNeise, D.D.NeiseNoethe, M.M.NoetheBIGONGIARI, CiroCiroBIGONGIARIParavac, A.A.ParavacRhode, W.W.RhodeSchleicher, B.B.SchleicherSliusar, V.V.SliusarWalter, R.R.WalterD'AMMANDO, FilippoFilippoD'AMMANDOHoran, D.D.HoranLien, A. Y.A. Y.LienBaloković, M.M.BalokovićMadejski, G. M.G. M.MadejskiBlanch, O.O.BlanchPERRI, MatteoMatteoPERRIVERRECCHIA, FrancescoFrancescoVERRECCHIALeto, C.C.LetoLähteenmäki, A.A.LähteenmäkiTornikoski, M.M.TornikoskiRamakrishnan, V.V.RamakrishnanJärvelä, E.E.JärveläVera, R. J. C.R. J. C.VeraChamani, W.W.ChamaniVILLATA, MassimoMassimoVILLATABošnjak, Ž.Ž.BošnjakRAITERI, Claudia MariaClaudia MariaRAITERIGupta, A. C.A. C.GuptaPandey, A.A.PandeyFuentes, A.A.FuentesAgudo, I.I.AgudoCasadio, C.C.CasadioSemkov, E.E.SemkovIbryamov, S.S.IbryamovMarchini, A.A.MarchiniBachev, R.R.BachevBusetto, G.G.BusettoStrigachev, A.A.StrigachevOvcharov, E.E.OvcharovBozhilov, V.V.BozhilovValcheva, A.A.ValchevaZaharieva, E.E.ZaharievaDamljanovic, G.G.DamljanovicVince, O.O.VinceLarionov, V. M.V. M.LarionovBorman, G. A.G. A.BormanGrishina, T. S.T. S.GrishinaCarosi, R.R.CarosiHagen-Thorn, V. A.V. A.Hagen-ThornKopatskaya, E. N.E. N.KopatskayaLarionova, E. G.E. G.LarionovaLarionova, L. V.L. V.LarionovaMorozova, D. A.D. A.MorozovaNikiforova, A. A.A. A.NikiforovaSavchenko, S. S.S. S.SavchenkoTroitskiy, I. S.I. S.TroitskiyTroitskaya, Y. V.Y. V.TroitskayaVasilyev, A. A.A. A.VasilyevCeribella, G.G.CeribellaMerkulova, O. A.O. A.MerkulovaChen, W. P.W. P.ChenSamal, M.M.SamalLin, H. C.H. C.LinMoody, J. W.J. W.MoodySadun, A. C.A. C.SadunJorstad, S. G.S. G.JorstadMarscher, A. P.A. P.MarscherWeaver, Z. R.Z. R.WeaverFeige, M.M.FeigeCerruti, M.M.CerrutiKania, J.J.KaniaKopp, M.M.KoppKunkel, L.L.KunkelReinhart, D.D.ReinhartScherbantin, A.A.ScherbantinSchneider, L.L.SchneiderLorey, C.C.LoreyAcosta-Pulido, J. A.J. A.Acosta-PulidoCARNERERO MARTIN, Maria IsabelMaria IsabelCARNERERO MARTINCarosati, D.D.CarosatiChai, Y.Y.ChaiKurtanidze, S. O.S. O.KurtanidzeKurtanidze, O. M.O. M.KurtanidzeNikolashvili, M. G.M. G.NikolashviliChigladze, R. A.R. A.ChigladzeIvanidze, R. Z.R. Z.IvanidzeKimeridze, G. N.G. N.KimeridzeSigua, L. A.L. A.SiguaJoner, M. D.M. D.JonerSpencer, M.M.SpencerGIROLETTI, MarcelloMarcelloGIROLETTIChilingarian, A.A.ChilingarianMARCHILI, NicolaNicolaMARCHILIRIGHINI, SimonaSimonaRIGHINIRizzi, N.N.RizziBONNOLI, GiacomoGiacomoBONNOLICikota, S.S.CikotaColak, S. M.S. M.ColakColombo, E.E.ColomboContreras, J. L.J. L.ContrerasCortina, J.J.CortinaCOVINO, StefanoStefanoCOVINOD'Amico, G.G.D'AmicoD'Elia, V.V.D'Eliada Vela, P.P.da VelaDAZZI, FrancescoFrancescoDAZZIde Angelis, A.A.de Angelisde Lotto, B.B.de LottoDelfino, M.M.DelfinoDelgado, J.J.DelgadoDelgado Mendez, C.C.Delgado MendezDepaoli, D.D.Depaolidi Pierro, F.F.di Pierrodi Venere, L.L.di VenereDo Souto Espiñeira, E.E.Do Souto EspiñeiraDominis Prester, D.D.Dominis PresterDonini, A.A.DoniniDoro, M.M.DoroFallah Ramazani, V.V.Fallah RamazaniFattorini, A.A.FattoriniFerrara, G.G.FerraraFonseca, M. V.M. V.FonsecaFont, L.L.FontFruck, C.C.FruckFukami, S.S.FukamiGarcía López, R. J.R. J.García LópezGarczarczyk, M.M.GarczarczykGasparyan, S.S.GasparyanGaug, M.M.GaugGiglietto, N.N.GigliettoGiordano, F.F.GiordanoGliwny, P.P.GliwnyGodinović, N.N.GodinovićGREEN, JARRED GERSHONJARRED GERSHONGREENGreen, D.D.GreenHadasch, D.D.HadaschHahn, A.A.HahnHeckmann, L.L.HeckmannHerrera, J.J.HerreraHoang, J.J.HoangHrupec, D.D.HrupecHütten, M.M.HüttenInada, T.T.InadaInoue, S.S.InoueIshio, K.K.IshioIwamura, Y.Y.IwamuraJiménez, I.I.JiménezJormanainen, J.J.JormanainenJouvin, L.L.JouvinKajiwara, Y.Y.KajiwaraKarjalainen, M.M.KarjalainenKerszberg, D.D.KerszbergKobayashi, Y.Y.KobayashiKubo, H.H.KuboKushida, J.J.KushidaLAMASTRA, AlessandraAlessandraLAMASTRALelas, D.D.LelasLEONE, FrancescoFrancescoLEONELindfors, E.E.LindforsLOMBARDI, SaverioSaverioLOMBARDILongo, F.F.LongoLópez-Coto, R.R.López-CotoLópez-Moya, M.M.López-MoyaLópez-Oramas, A.A.López-OramasLoporchio, S.S.LoporchioMachado de Oliveira Fraga, B.B.Machado de Oliveira FragaMaggio, C.C.Maggio2025-02-252025-02-2520210004-6361http://hdl.handle.net/20.500.12386/36223<BR /> 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. <BR /> 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. <BR /> 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'<SUB>min</SUB>=2×10<SUP>4</SUP> to γ'<SUB>max</SUB>=6×10<SUP>5</SUP>. <P />Light curves and spectral energy distributions data are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/655/A89">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/655/A89</A>STAMPAenArticle10.1051/0004-6361/2021410042-s2.0-85121042376https://www.aanda.org/articles/aa/full_html/2021/11/aa41004-21/aa41004-21.html2021A&A...655A..89MFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation