Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and $\gamma$-ray activity in 2015$-$2016

Abstract

We report a characterization of the multi-band 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 November 2014 till June 2016. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F${}_{>1\mathrm{TeV}}<$ 1.7$\times$10${}^{-12}$ ph cm${}^{-2}$ s${}^{-1}$) and in the 2-10 keV (X-ray) band (F${}_{2-10\mathrm{keV}}<$3.6$\times$10${}^{-11}$ erg cm${}^{-2}$ s${}^{-1}$), during which the Swift-BAT data suggests 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 HR${}_{\mathrm{keV}}$ and HR${}_{\mathrm{TeV}}$ 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 days centered at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 days centered at a time lag of $43_{-6}^{+9}$ days.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.

45 pages, 30 figures, 6 tables, accepted for publication in MNRAS

References in corpus (19)

• The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
• Kinematics of Parsec-Scale Jets of Gamma-Ray Blazars at 43~GHz within the VLBA-BU-BLAZAR Program
• Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability
• Multiwaveband Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Correlated Polarization Behavior
• Observations of Mkn 421 with the MAGIC Telescope
• Time-correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission
• Host galaxy subtraction of TeV candidate BL Lacertae objects
• Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010
• Superorbital variability of X-ray and radio emission of Cyg X-1 - II. Dependence of the orbital modulation and spectral hardness on the superorbital phase
• Locating the gamma-ray emission site in Fermi/LAT blazars from correlation analysis between 37 GHz radio and gamma-ray light curves
• A combined radio and GeV gamma-ray view of the 2012 and 2013 flares of Mrk 421
• Polarization Signatures of Kink Instabilities in the Blazar Emission Region from Relativistic Magnetohydrodynamic Simulations
• On the origin of the hard X-Ray excess of high-synchrotron-peaked BL Lac object Mrk 421
• Bimodal radio variability in OVRO-40m-monitored blazars
• Very Long Baseline polarimetry and the gamma-ray connection in Markarian 421 during the broadband campaign in 2011
• Systematic Physical Characterization of the Gamma-Ray Spectra of 2FHL Blazars
• Flux Distribution of Gamma-Ray Emission in Blazars: The Example of Mrk 501
• Zenith angle dependence of the cosmic ray rate as measured with Imaging air-Cherenkov Telescopes
• A flat-spectrum flare in S4 0444+63 revealed by a new implementation of multi-wavelength single-dish observations

Cited by in corpus (21)

• Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017
• Multi-messenger characterization of Mrk 501 during historically low X-ray and $\gamma$-ray activity
• The first hard X-ray spectral catalogue of Blazars observed by NuSTAR
• The variability of blazars throughout the electromagnetic spectrum
• Characterizing the optical nature of the blazar S5 1803+784 during its 2020 flare
• Broadband study of BL Lac during flare of 2020: Spectral evolution and emergence of HBL component
• Flaring activity from magnetic reconnection in BL Lacertae
• The variability patterns of the TeV blazar PG 1553+113 from a decade of MAGIC and multi-band observations
• Multi-wavelength Variation Phenomena of PKS 0735+178 on Diverse Timescale
• On the narrow spectral feature at $\sim$3 TeV in the MAGIC spectrum of Mrk 501
• Two-injection scenario for the hard X-ray excess observed in Mrk 421
• Imprint of "Local Opacity" Effect in Gamma-Ray Spectrum of Blazar Jet
• Time-Dependent Modeling of the Sub-Hour Spectral Evolution During the 2013 Outburst of Mrk 421
• VHE $\gamma$-ray observations of bright BL Lacs with the Large-Sized Telescope prototype (LST-1) of the CTAO
• Variability Signatures of a Burst Process in Flaring Gamma-ray Blazars
• GeV-radio correlation in Markarian 421
• Characterizing the Variable X-ray and UV-Optical Flux Behavior of Blazars
• Characterizing Long-term Optical Variability Properties of $\gamma$-ray Bright Blazars
• Relentless multi-wavelength variability of Mrk 421 and Mrk 501
• Shortterm optical variability of 4C 29.45
• The Major Gamma-ray Imaging Cherenkov Telescopes (MAGIC)