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Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017 Cerruti, Matteo Molina, Edgar Paredes i Poy, Josep Maria Ribó Gomis, Marc MAGIC Collaboration Galàxies actives Cosmologia Radiació Active galaxies Cosmology Radiation We report a characterization of the multiband flux variability and correlations of the nearby (z = 0.031) blazar Markarian 421 (Mrk 421) using data from Metsähovi, Swift, Fermi-LAT, MAGIC, FACT, and other collaborations and instruments from 2014 November till 2016 June. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F>1 TeV < 1.7 × 10−12 ph cm−2 s−1) and in the 2–10 keV (X-ray) band (F erg cm−2 s−1), during which the Swift-BAT data suggest an additional spectral component beyond the regular synchrotron emission. The highest flux variability occurs in X-rays and very high-energy (E > 0.1 TeV) γ-rays, which, despite the low activity, show a significant positive correlation with no time lag. The HRkeV and HRTeV show the harder-when-brighter trend observed in many blazars, but the trend flattens at the highest fluxes, which suggests a change in the processes dominating the blazar variability. Enlarging our data set with data from years 2007 to 2014, we measured a positive correlation between the optical and the GeV emission over a range of about 60 d centred at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 d centred at a time lag of d. This observation is consistent with the radio-bright zone being located about 0.2 parsec downstream from the optical/GeV emission regions of the jet. The flux distributions are better described with a lognormal function in most of the energy bands probed, indicating that the variability in Mrk 421 is likely produced by a multiplicative process. 2025-03-19T18:46:07Z 2025-03-19T18:46:07Z 2021-11 2025-03-19T18:46:07Z info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Reproducció del document publicat a: https://doi.org/10.1093/mnras/staa3727 Astronomy & Astrophysics, 2021, vol. 655, p. id.A89, 36 pp https://doi.org/10.1093/mnras/staa3727 (c) The European Southern Observatory (ESO), 2021 info:eu-repo/semantics/openAccess EDP Sciences Articles publicats en revistes (Física Quàntica i Astrofísica)