2026-06-29T03:08:20Zhttps://docta.ucm.es/rest/oai/request

oai:docta.ucm.es:20.500.14352/84302024-09-05T17:37:24Zcom_20.500.14352_14col_20.500.14352_15

00925njm 22002777a 4500 dc Baquero Larriva, Orlando Andrés author Barrio Uña, Juan Abel author Contreras González, José Luis author Fonseca González, María Victoria author Hoang, Kim Dinh author López Moya, Marcos author Miener, Tjark author Miranda Pantoja, José Miguel author Morcuende, D. author Peñil Del Campo, Pablo author Saha, Lab author 2021-06 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 Metsahovi, 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 x 10(-12) ph cm(-2) s(-1)) and in the 2-10 keV (X-ray) band (F2-10 keV < 3.6 x 10(-11) 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) gamma-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 43(-6)(+9) 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. 0035-8711 10.1093/mnras/staa3727 https://hdl.handle.net/20.500.14352/8430 https://doi.org/10.1093/mnras/staa3727 https://academic.oup.com/mnras/ Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and gamma-ray activity in 2015-2016