TY - JOUR
T1 - Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and γ-ray activity in 2015-2016
AU - Acciari, V. A.
AU - Ansoldi, S.
AU - Antonelli, L. A.
AU - Asano, K.
AU - Babić, A.
AU - Banerjee, B.
AU - Baquero, A.
AU - Barres De Almeida, U.
AU - Barrio, J. A.
AU - Becerra González, J.
AU - Bednarek, W.
AU - Bellizzi, L.
AU - Bernardini, E.
AU - Bernardos, M.
AU - Berti, A.
AU - Besenrieder, J.
AU - Bhattacharyya, W.
AU - Bigongiari, C.
AU - Blanch, O.
AU - Bonnoli, G.
AU - Bošnjak, Z.
AU - Busetto, G.
AU - Carosi, R.
AU - Ceribella, G.
AU - Cerruti, M.
AU - Chai, Y.
AU - Chilingarian, A.
AU - Cikota, S.
AU - Colak, S. M.
AU - Colombo, E.
AU - Contreras, J. L.
AU - Cortina, J.
AU - Covino, S.
AU - D'Amico, G.
AU - D'Elia, V.
AU - Da Vela, P.
AU - Dazzi, F.
AU - De Angelis, A.
AU - De Lotto, B.
AU - Delfino, M.
AU - Delgado, J.
AU - Delgado Mendez, C.
AU - Depaoli, D.
AU - Fallah Ramazani, V.
AU - Karjalainen, Marie
AU - Will, M.
AU - Lähteenmäki, A.
AU - Tornikoski, M.
AU - Ramakrishnan, V.
AU - Järvelä, E.
AU - Vera Rodríguez, Rafael
AU - MAGIC Collaboration
AU - FACT Collaboration
N1 - Publisher Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2021/6/1
Y1 - 2021/6/1
N2 - 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 2-10, keV< 3.6× 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) 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 43+9-6 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.
AB - 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 2-10, keV< 3.6× 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) 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 43+9-6 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.
KW - BL Lacertae objects: individual: Mrk 421
KW - galaxies: active
KW - methods: data analysis
KW - methods: observational
KW - radiation mechanisms: non-thermal
UR - http://www.scopus.com/inward/record.url?scp=85107947535&partnerID=8YFLogxK
U2 - 10.1093/mnras/staa3727
DO - 10.1093/mnras/staa3727
M3 - Article
AN - SCOPUS:85107947535
VL - 504
SP - 1427
EP - 1451
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 1
ER -