Multiwavelength observations of Markarian 421 in 2001 March

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, Abraham David 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 & 9 others S. LeBohec, K. Lee, P. Moriarty, R. A. Ong, D. Petry, J. Quinn, G. H. Sembroski, S. P. Wakely, T. C. Weekes

Research output: Contribution to journalArticle

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Abstract

We present a detailed analysis of week-long simultaneous observations of the blazar Mrk 421 at 2-60 keV X-rays (RXTE) and TeV γ-rays (Whipple and HEGRA) in 2001. Accompanying optical monitoring was performed with the Mt. Hopkins 48 inch telescope. The unprecedented quality of this data set enables us to establish the existence of the correlation between the TeV and X-ray luminosities, and also to start unveiling some of its characteristics, in particular its energy dependence and time variability. The source shows strong variations in both X-ray and γ-ray bands, which are highly correlated. No evidence of an X-ray γ-ray interband lag τ is found on the full week data set, with T τ≲3 ks. A detailed analysis of the March 19 flare, however, 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 γ-ray variations are also highly correlated, and the TeV luminosity increases more than linearly with respect to the X-ray one. The high degree of correlation lends further support to the standard model in which a unique electron population produces the X-rays by synchrotron radiation and the γ-ray component by inverse Compton scattering. However, the finding that for the individual best observed flares the γ-ray flux scales approximately quadratically with respect to the X-ray flux poses a serious challenge to emission models for TeV blazars, as it requires rather special conditions and/or fine tuning of the temporal evolution of the physical parameters of the emission region. We briefly discuss the astrophysical consequences of these new findings in the context of the competing models for the jet emission in blazars.

Original languageEnglish (US)
Pages (from-to)906-925
Number of pages20
JournalAstrophysical Journal
Volume677
Issue number2
DOIs
StatePublished - Apr 20 2008

Fingerprint

rays
x rays
blazars
flares
time lag
luminosity
X Ray Timing Explorer
temporal evolution
outburst
astrophysics
synchrotron radiation
tuning
scattering
telescopes
electron
monitoring
estimates
energy
electrons
analysis

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Fossati, G., Buckley, J. H., Bond, I. H., Bradbury, S. M., Carter-Lewis, D. A., Chow, Y. C. K., ... Weekes, T. C. (2008). Multiwavelength observations of Markarian 421 in 2001 March: An unprecedented view on the X-rAY/TeV correlated variability. Astrophysical Journal, 677(2), 906-925. https://doi.org/10.1086/527311
Fossati, G. ; Buckley, J. H. ; Bond, I. H. ; Bradbury, S. M. ; Carter-Lewis, D. A. ; Chow, Y. C.K. ; Cui, W. ; Falcone, Abraham David ; Finley, J. P. ; Gaidos, J. A. ; Grube, J. ; Holder, J. ; Horan, D. ; Horns, D. ; Jordan, M. M. ; Kieda, D. B. ; Kildea, J. ; Krawczynski, H. ; Krennrich, F. ; Lang, M. J. ; LeBohec, S. ; Lee, K. ; Moriarty, P. ; Ong, R. A. ; Petry, D. ; Quinn, J. ; Sembroski, G. H. ; Wakely, S. P. ; Weekes, T. C. / Multiwavelength observations of Markarian 421 in 2001 March : An unprecedented view on the X-rAY/TeV correlated variability. In: Astrophysical Journal. 2008 ; Vol. 677, No. 2. pp. 906-925.
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title = "Multiwavelength observations of Markarian 421 in 2001 March: An unprecedented view on the X-rAY/TeV correlated variability",
abstract = "We present a detailed analysis of week-long simultaneous observations of the blazar Mrk 421 at 2-60 keV X-rays (RXTE) and TeV γ-rays (Whipple and HEGRA) in 2001. Accompanying optical monitoring was performed with the Mt. Hopkins 48 inch telescope. The unprecedented quality of this data set enables us to establish the existence of the correlation between the TeV and X-ray luminosities, and also to start unveiling some of its characteristics, in particular its energy dependence and time variability. The source shows strong variations in both X-ray and γ-ray bands, which are highly correlated. No evidence of an X-ray γ-ray interband lag τ is found on the full week data set, with T τ≲3 ks. A detailed analysis of the March 19 flare, however, 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 γ-ray variations are also highly correlated, and the TeV luminosity increases more than linearly with respect to the X-ray one. The high degree of correlation lends further support to the standard model in which a unique electron population produces the X-rays by synchrotron radiation and the γ-ray component by inverse Compton scattering. However, the finding that for the individual best observed flares the γ-ray flux scales approximately quadratically with respect to the X-ray flux poses a serious challenge to emission models for TeV blazars, as it requires rather special conditions and/or fine tuning of the temporal evolution of the physical parameters of the emission region. We briefly discuss the astrophysical consequences of these new findings in the context of the competing models for the jet emission in blazars.",
author = "G. Fossati and Buckley, {J. H.} and Bond, {I. H.} and Bradbury, {S. M.} and Carter-Lewis, {D. A.} and Chow, {Y. C.K.} and W. Cui and Falcone, {Abraham David} and Finley, {J. P.} and Gaidos, {J. A.} and J. Grube and J. Holder and D. Horan and D. Horns and Jordan, {M. M.} and Kieda, {D. B.} and J. Kildea and H. Krawczynski and F. Krennrich and Lang, {M. J.} and S. LeBohec and K. Lee and P. Moriarty and Ong, {R. A.} and D. Petry and J. Quinn and Sembroski, {G. H.} and Wakely, {S. P.} and Weekes, {T. C.}",
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Fossati, G, Buckley, JH, Bond, IH, Bradbury, SM, Carter-Lewis, DA, Chow, YCK, Cui, W, Falcone, AD, Finley, JP, Gaidos, JA, Grube, J, Holder, J, Horan, D, Horns, D, Jordan, MM, Kieda, DB, Kildea, J, Krawczynski, H, Krennrich, F, Lang, MJ, LeBohec, S, Lee, K, Moriarty, P, Ong, RA, Petry, D, Quinn, J, Sembroski, GH, Wakely, SP & Weekes, TC 2008, 'Multiwavelength observations of Markarian 421 in 2001 March: An unprecedented view on the X-rAY/TeV correlated variability', Astrophysical Journal, vol. 677, no. 2, pp. 906-925. https://doi.org/10.1086/527311

Multiwavelength observations of Markarian 421 in 2001 March : An unprecedented view on the X-rAY/TeV correlated variability. / Fossati, G.; Buckley, J. H.; Bond, I. H.; Bradbury, S. M.; Carter-Lewis, D. A.; Chow, Y. C.K.; Cui, W.; Falcone, Abraham David; Finley, J. P.; Gaidos, J. A.; Grube, J.; Holder, J.; Horan, D.; Horns, D.; Jordan, M. M.; Kieda, D. B.; Kildea, J.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Lee, K.; Moriarty, P.; Ong, R. A.; Petry, D.; Quinn, J.; Sembroski, G. H.; Wakely, S. P.; Weekes, T. C.

In: Astrophysical Journal, Vol. 677, No. 2, 20.04.2008, p. 906-925.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Multiwavelength observations of Markarian 421 in 2001 March

T2 - An unprecedented view on the X-rAY/TeV correlated variability

AU - Fossati, G.

AU - Buckley, J. H.

AU - Bond, I. H.

AU - Bradbury, S. M.

AU - Carter-Lewis, D. A.

AU - Chow, Y. C.K.

AU - Cui, W.

AU - Falcone, Abraham David

AU - Finley, J. P.

AU - Gaidos, J. A.

AU - Grube, J.

AU - Holder, J.

AU - Horan, D.

AU - Horns, D.

AU - Jordan, M. M.

AU - Kieda, D. B.

AU - Kildea, J.

AU - Krawczynski, H.

AU - Krennrich, F.

AU - Lang, M. J.

AU - LeBohec, S.

AU - Lee, K.

AU - Moriarty, P.

AU - Ong, R. A.

AU - Petry, D.

AU - Quinn, J.

AU - Sembroski, G. H.

AU - Wakely, S. P.

AU - Weekes, T. C.

PY - 2008/4/20

Y1 - 2008/4/20

N2 - We present a detailed analysis of week-long simultaneous observations of the blazar Mrk 421 at 2-60 keV X-rays (RXTE) and TeV γ-rays (Whipple and HEGRA) in 2001. Accompanying optical monitoring was performed with the Mt. Hopkins 48 inch telescope. The unprecedented quality of this data set enables us to establish the existence of the correlation between the TeV and X-ray luminosities, and also to start unveiling some of its characteristics, in particular its energy dependence and time variability. The source shows strong variations in both X-ray and γ-ray bands, which are highly correlated. No evidence of an X-ray γ-ray interband lag τ is found on the full week data set, with T τ≲3 ks. A detailed analysis of the March 19 flare, however, 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 γ-ray variations are also highly correlated, and the TeV luminosity increases more than linearly with respect to the X-ray one. The high degree of correlation lends further support to the standard model in which a unique electron population produces the X-rays by synchrotron radiation and the γ-ray component by inverse Compton scattering. However, the finding that for the individual best observed flares the γ-ray flux scales approximately quadratically with respect to the X-ray flux poses a serious challenge to emission models for TeV blazars, as it requires rather special conditions and/or fine tuning of the temporal evolution of the physical parameters of the emission region. We briefly discuss the astrophysical consequences of these new findings in the context of the competing models for the jet emission in blazars.

AB - We present a detailed analysis of week-long simultaneous observations of the blazar Mrk 421 at 2-60 keV X-rays (RXTE) and TeV γ-rays (Whipple and HEGRA) in 2001. Accompanying optical monitoring was performed with the Mt. Hopkins 48 inch telescope. The unprecedented quality of this data set enables us to establish the existence of the correlation between the TeV and X-ray luminosities, and also to start unveiling some of its characteristics, in particular its energy dependence and time variability. The source shows strong variations in both X-ray and γ-ray bands, which are highly correlated. No evidence of an X-ray γ-ray interband lag τ is found on the full week data set, with T τ≲3 ks. A detailed analysis of the March 19 flare, however, 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 γ-ray variations are also highly correlated, and the TeV luminosity increases more than linearly with respect to the X-ray one. The high degree of correlation lends further support to the standard model in which a unique electron population produces the X-rays by synchrotron radiation and the γ-ray component by inverse Compton scattering. However, the finding that for the individual best observed flares the γ-ray flux scales approximately quadratically with respect to the X-ray flux poses a serious challenge to emission models for TeV blazars, as it requires rather special conditions and/or fine tuning of the temporal evolution of the physical parameters of the emission region. We briefly discuss the astrophysical consequences of these new findings in the context of the competing models for the jet emission in blazars.

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