Bibcode
Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Buson, S.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; de Oña Wilhelmi, E.; Di Pierro, F.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinović, N.; González Muñoz, A.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K. et al.
Bibliographical reference
Astronomy and Astrophysics, Volume 593, id.A91, 12 pp.
Advertised on:
9
2016
Journal
Citations
40
Refereed citations
38
Description
Aims: We study the multi-band variability and correlations of the
TeV blazar Mrk 421 on year timescales, which can bring additional
insight on the processes responsible for its broadband emission.
Methods: We observed Mrk 421 in the very high energy (VHE) γ-ray
range with the Cherenkov telescope MAGIC-I from March 2007 to June 2009
for a total of 96 h of effective time after quality cuts. The VHE flux
variability is quantified using several methods, including the Bayesian
Block algorithm, which is applied to data from Cherenkov telescopes here
for the first time. The 2.3 yr long MAGIC light curve is complemented
with data from the Swift/BAT and RXTE/ASM satellites and the KVA,
GASP-WEBT, OVRO, and Metsähovi telescopes from February 2007 to
July 2009, allowing for an excellent characterisation of the multi-band
variability and correlations over year timescales. Results: Mrk
421 was found in different γ-ray emission states during the 2.3 yr
long observation period: The flux above 400 GeV spans from the minimum
nightly value of (1.3 ± 0.4)×10-11
cm-2 s-1 to the maximum flux, that is about 24
times higher, at (3.1 ± 0.1)×10-10
cm-2 s-1. Flares and different levels of
variability in the γ-ray light curve could be identified with the
Bayesian Block algorithm. The same behaviour of a quiet and active
emission was found in the X-ray light curves measured by Swift/BAT and
the RXTE/ASM, with a direct correlation in time. The behaviour of the
optical light curve of GASP-WEBT and the radio light curves by OVRO and
Metsähovi are different as they show no coincident features with
the higher energetic light curves and a less variable emission. Overall,
the fractional variability increases with energy. The comparable
variability in the X-ray and VHE bands and their direct correlation
during both high- and low-activity periods spanning many months show
that the electron populations radiating the X-ray and γ-ray
photons are either the same, as expected in the synchrotron-self-Compton
mechanism, or at least strongly correlated, as expected in
electromagnetic cascades.
The complete data set shown in Fig. 2 and the data points shown in Figs.
3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A91