Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017
Acciari VA; Ansoldi S; Antonelli LA; Engels AA; Artero M; Asano K; Baquero A; de Almeida UB; Barrio JA; Gonzalez JB; Bednarek W; Bellizzi L; Bernardini E; Bernardos M; Berti A; Besenrieder J; Bhattacharyya W; Bigongiari C; Blanch O; Bosnjak Z; Busetto G; Carosi R; Ceribella G; Cerruti M; Chai Y; Chilingarian A; Cikota S; Colak SM; Colombo E; Contreras JL; Cortina J; Covino S; D'Amico G; D'Elia V; DaVela P; Dazzi F; De Angelis A; De Lotto B; Delfino M; Delgado J; Mendez CD; Depaoli D; Di Pierro F; DiVenere L; Espineira ED; Prester DD; Donini A; Doro M; Ramazani VF; Fattorini A; Ferrara G; Fonseca MV; Font L; Fruck C; Fukami S; Lopez RJG; Garczarczyk M; Gasparyan S; Gaug M; Giglietto N; Giordano F; Gliwny P; Green JG; Green D; Hadasch D; Hahn A; Heckmann L; Herrera J; Hoang J; Hrupec D; Hutten M; Inada T; Inoue S; Ishio K; Iwamura Y; Jimenez I; Jormanainen J; Jouvin L; Kajiwara Y; Karjalainen M; Kerszberg D; Kobayashi Y; Kubo H; Kushida J; Lamastra A; Lelas D; Leone F; Lindfors E; Lombardi S; Longo F; Lopez-Coto R; Lopez-Moya M; Lopez-Oramas A; Loporchio S; Fraga BMD; Maggio C; Majumdar P; Makariev M; Mallamaci M; Maneva G; Manganaro M; Maraschi L; Mariotti M; Martinez M; Mazin D; Menchiari S; Mender S; Miceli D; Miener T; Minev M; Miranda JM; Mirzoyan R; Molina E; Moralejo A; Morcuende D; Moreno V; Moretti E; Neustroev V; Nigro C; Nilsson K; Nishijima K; Noda K; Nozaki S; Ohtani Y; Oka T; Otero-Santos J; Paiano S; Palatiello M; Paneque D; Paoletti R; Paredes JM; Penil P; Perennes C; Persic M; Moroni PGP; Prandini E; Priyadarshi C; Puljak I; Ribo M; Rico J; Righi C; Rugliancich A; Saha L; Sahakyan N; Saito T; Sakurai S; Satalecka K; Saturni FG; Schmidt K; Schweizer T; Sitarek J; Snidaric I; Sobczynska D; Spolon A; Stamerra A; Strom D; Strzys M; Suda Y; Takahashi M; Tavecchio F; Temnikov P; Teshima M; Tosti L; Truzzi S; Tutone A; Ubach S; van Scherpenberg J; Vanzo G; Acosta MV; Ventura S; Verguilov V; Vigorito CF; Vitale V; Vovk I; Will M; Wunderlich C; Zaric D; Baack D; Balbo M; Biederbeck N; Biland A; Bretz T; Buss J; Dorner D; Eisenberger L; Elsaesser D; Hildebrand D; Iotov R; Mannheim K; Neise D; Noethe M; Paravac A; Rhode W; Schleicher B; Sliusar V; Walter R; D'Ammando F; Horan D; Lien AY; Balokovic M; Madejski GM; Perri M; Verrecchia F; Leto C; Lahteenmaki A; Tornikoski M; Ramakrishnan V; Jarvela E; Vera RJC; Villata M; Raiteri CM; Gupta AC; Pandey A; Fuentes A; Agudo I; Casadio C; Semkov E; Ibryamov S; Marchini A; Bachev R; Strigachev A; Ovcharov E; Bozhilov V; Valcheva A; Zaharieva E; Damljanovic G; Vince O; Larionov VM; Borman GA; Grishina TS; Hagen-Thorn VA; Kopatskaya EN; Larionova EG; Larionova LV; Morozova DA; Nikiforova AA; Savchenko SS; Troitskiy IS; Troitskaya YV; Vasilyev AA; Merkulova OA; Chen WP; Samal M; Lin HC; Moody JW; Sadun AC; Jorstad SG; Marscher AP; Weaver ZR; Feige M; Kania J; Kopp M; Kunkel L; Reinhart D; Scherbantin A; Schneider L; Lorey C; Acosta-Pulido JA; Carnerero MI; Carosati D; Kurtanidze SO; Kurtanidze OM; Nikolashvili MG; Chanishvili RG; Chigladze RA; Ivanidze RZ; Kimeridze GN; Sigua LA; Joner MD; Spencer M; Giroletti M; Marchili N; Righini S; Rizzi N; Bonnoli G
https://urn.fi/URN:NBN:fi-fe2022012711100
Tiivistelmä
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 Metsahovi. 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 3 sigma. 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 gamma(min)' = 2 x 10(4) to gamma(max)' = 6 x 10(5).
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