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arXiv · 0710.4138

Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability

G. Fossati·J. H. Buckley·I. H. Bond·S. M. Bradbury·D. A. Carter-Lewis·Y. C. K. Chow·W. Cui·A. D. Falcone·J. P. Finley·J. A. Gaidos·J. Grube·J. Holder·D. Horan·D. Horns·M. M. Jordan·D. B. Kieda·J. Kildea·H. Krawczynski·F. Krennrich·M. J. Lang·S. LeBohec·K. Lee·P. Moriarty·R. A. Ong·D. Petry·J. Quinn·G. H. Sembroski·S. P. Wakely·T. C. Weekes
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Abstract

(Abridged) We present a detailed analysis of week-long simultaneous observations of the blazar Mrk421 at 2-60 keV X-rays (RXTE) and TeV gamma-rays (Whipple and HEGRA) in 2001. The unprecedented quality of this dataset enables us to establish firmly the existence of the correlation between the TeV and X-ray luminosities, and to start unveiling some of its more detailed characteristics, in particular its energy dependence, and time variability. The source shows strong, highly correlated variations in X-ray and gamma-ray. No evidence of X-ray/gamma-ray interband lag is found on the full week dataset (<3 ks). However, a detailed analysis of the March 19 flare reveals that data are not consistent with the peak of the outburst in the 2-4 keV X-ray and TeV band being simultaneous. We estimate a 2.1+/-0.7 ks TeV lag. The amplitudes of the X-ray and gamma-ray variations are also highly correlated, and the TeV luminosity increases more than linearly w.r.t. the X-ray one. The strong correlation supports the standard model in which a unique electrons population produces the X-rays by synchrotron radiation and the gamma-ray component by inverse Compton scattering. However, for the individual best observed flares the gamma-ray flux scales approximately quadratically w.r.t. the X-ray flux, posing a serious challenge to emission models for TeV blazars. Rather special conditions and/or fine tuning of the temporal evolution of the physical parameters of the emission region are required in order to reproduce the quadratic correlation.

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G. Fossati, J. H. Buckley, I. H. Bond, S. M. Bradbury, D. A. Carter-Lewis, Y. C. K. Chow, W. Cui, A. D. Falcone, J. P. Finley, J. A. Gaidos, J. Grube, J. Holder, D. Horan, D. Horns, M. M. Jordan, D. B. Kieda, J. Kildea, H. Krawczynski, F. Krennrich, M. J. Lang, S. LeBohec, K. Lee, P. Moriarty, R. A. Ong, D. Petry, J. Quinn, G. H. Sembroski, S. P. Wakely, T. C. Weekes. 2008-06-16. Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability. https://doi.org/10.1086/527311

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