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