2026-06-27T23:18:10Zhttps://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

Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and gamma-ray activity in 2015-2016 Baquero Larriva, Orlando Andrés Barrio Uña, Juan Abel Contreras González, José Luis Fonseca González, María Victoria Hoang, Kim Dinh López Moya, Marcos Miener, Tjark Miranda Pantoja, José Miguel Morcuende, D. Peñil Del Campo, Pablo Saha, Lab 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. 2023-06-17T09:13:35Z 2023-06-17T09:13:35Z 2023-06-17T09:13:35Z 2021-06 journal article https://hdl.handle.net/20.500.14352/8430 0035-8711 10.1093/mnras/staa3727 eng (FPA2017-87859- P, FPA2017-85668-P, FPA2017-82729-C6-2-R, FPA2017-82729- C6-6-R, FPA2017-82729-C6-5-R, AYA2015-71042-P, AYA2016- 76012-C3-1-P, ESP2017-87055-C2-2-P, FPA2017-90566-REDC) (SEV-2016-0588; SEV-2015-0548) MDM-2014-0369 DO1-268/16.12.2019 320045 LCF/BQ/PI18/11630012 IP-2016-06-9782 13.12.1.3.02 SFB823/C4 SFB876/C3 DE-AC02-76SF00515 UMO-2016/22/M/ST9/00382 80NSSC17K0649 ETH-10.082 ETH-27.12-1 SFB 876 NNX08AW31G NNX11A043G NNX14AQ89G AST-0808050 AST-1109911 open access Wiley