Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71

L. Fuhrmann, T. P. Krichbaum, A. Witzel, A. Kraus, S. Britzen, S. Bernhart, C. M V Impellizzeri, I. Agudo, J. Klare, B. W. Sohn, E. Angelakis, U. Bach, K. É Gabányi, E. Körding, A. Pagels, J. A. Zensus, S. J. Wagner, L. Ostorero, H. Ungerechts, M. GrewingM. Tornikoski, A. J. Apponi, B. Vila-Vilaró, Lucy M Ziurys, R. G. Strom

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Abstract

Aims. The BL Lac object S5 0716+71 was observed in a global multi-frequency campaign to search for rapid and correlated flux density variability and signatures of an inverse-Compton (IC) catastrophe during the states of extreme apparent brightness temperatures. Methods. The observing campaign involved simultaneous ground-based monitoring at radio to IR/optical wavelengths and was centered around a 500-ks pointing with the INTEGRAL satellite (November 10-17, 2003). Here, we present the combined analysis and results of the radio observations, covering the cm- to sub-mm bands. This facilitates a detailed study of the variability characteristics of an inter- to intra-day variable IDV source from cm- to the short mm-bands. We further aim to constrain the variability brightness temperatures (TB) and Doppler factors (∂) comparing the radio-bands with the hard X-ray emission, as seen by INTEGRAL at 3-200 keV. Results. 0716+714 was in an exceptionally high state and different (slower) phase of short-term variability, when compared to the past, most likely due to a pronounced outburst shortly before the campaign. The flux density variability in the cm- to mm-bands is dominated by a ~4 day time scale amplitude increase of up to ~35%, systematically more pronounced towards shorter wavelengths. The cross-correlation analysis reveals systematic time-lags with the higher frequencies varying earlier, similar to canonical variability on longer time-scales. The increase of the variability amplitudes with frequency contradicts expectations from standard interstellar scintillation (ISS) and suggests a source-intrinsic origin for the observed inter-day variability. We find an inverted synchrotron spectrum peaking near 90 GHz, with the peak flux increasing during the first 4 days. The lower limits to TBderived from the inter-day variations exceed the 1012 K IC-limit by up to 3-4 orders of magnitude. Assuming relativistic boosting, our different estimates of yield robust and self-consistent lower limits of ∂ ≥ 5-33 - in good agreement with ∂VLBIobtained from VLBI studies and the IC-Doppler factors ∂IC > 14-16 obtained from the INTEGRAL data. Conclusions. The non-detection of S5 0716+714 with INTEGRAL in this campaign excludes an excessively high X-ray flux associated with a simultaneous IC catastrophe. Since a strong contribution from ISS can be excluded, we conclude that relativistic Doppler boosting naturally explains the apparent violation of the theoretical limits. All derived Doppler factors are internally consistent, agree with the results from different observations and can be explained within the framework of standard synchrotron-self-Compton (SSC) jet models of AGN.

Original languageEnglish (US)
Pages (from-to)1019-1037
Number of pages19
JournalAstronomy and Astrophysics
Volume490
Issue number3
DOIs
StatePublished - Nov 2008

Fingerprint

radio
brightness temperature
wavelength
timescale
very long baseline interferometry
outburst
scintillation
synchrotrons
flux density
monitoring
very long base interferometry
radio observation
catastrophe
daytime
wavelengths
cross correlation
coverings
x rays
time lag
analysis

Keywords

  • BL Lacertae objects: general
  • BL Lacertae objects: individual: S5 0716+71.III
  • Galaxies: active
  • Quasars: general
  • Radiation mechanisms: non-thermal
  • Radio continuum: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Fuhrmann, L., Krichbaum, T. P., Witzel, A., Kraus, A., Britzen, S., Bernhart, S., ... Strom, R. G. (2008). Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71. Astronomy and Astrophysics, 490(3), 1019-1037. https://doi.org/10.1051/0004-6361:20078893

Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71. / Fuhrmann, L.; Krichbaum, T. P.; Witzel, A.; Kraus, A.; Britzen, S.; Bernhart, S.; Impellizzeri, C. M V; Agudo, I.; Klare, J.; Sohn, B. W.; Angelakis, E.; Bach, U.; Gabányi, K. É; Körding, E.; Pagels, A.; Zensus, J. A.; Wagner, S. J.; Ostorero, L.; Ungerechts, H.; Grewing, M.; Tornikoski, M.; Apponi, A. J.; Vila-Vilaró, B.; Ziurys, Lucy M; Strom, R. G.

In: Astronomy and Astrophysics, Vol. 490, No. 3, 11.2008, p. 1019-1037.

Research output: Contribution to journalArticle

Fuhrmann, L, Krichbaum, TP, Witzel, A, Kraus, A, Britzen, S, Bernhart, S, Impellizzeri, CMV, Agudo, I, Klare, J, Sohn, BW, Angelakis, E, Bach, U, Gabányi, KÉ, Körding, E, Pagels, A, Zensus, JA, Wagner, SJ, Ostorero, L, Ungerechts, H, Grewing, M, Tornikoski, M, Apponi, AJ, Vila-Vilaró, B, Ziurys, LM & Strom, RG 2008, 'Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71', Astronomy and Astrophysics, vol. 490, no. 3, pp. 1019-1037. https://doi.org/10.1051/0004-6361:20078893
Fuhrmann, L. ; Krichbaum, T. P. ; Witzel, A. ; Kraus, A. ; Britzen, S. ; Bernhart, S. ; Impellizzeri, C. M V ; Agudo, I. ; Klare, J. ; Sohn, B. W. ; Angelakis, E. ; Bach, U. ; Gabányi, K. É ; Körding, E. ; Pagels, A. ; Zensus, J. A. ; Wagner, S. J. ; Ostorero, L. ; Ungerechts, H. ; Grewing, M. ; Tornikoski, M. ; Apponi, A. J. ; Vila-Vilaró, B. ; Ziurys, Lucy M ; Strom, R. G. / Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71. In: Astronomy and Astrophysics. 2008 ; Vol. 490, No. 3. pp. 1019-1037.
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abstract = "Aims. The BL Lac object S5 0716+71 was observed in a global multi-frequency campaign to search for rapid and correlated flux density variability and signatures of an inverse-Compton (IC) catastrophe during the states of extreme apparent brightness temperatures. Methods. The observing campaign involved simultaneous ground-based monitoring at radio to IR/optical wavelengths and was centered around a 500-ks pointing with the INTEGRAL satellite (November 10-17, 2003). Here, we present the combined analysis and results of the radio observations, covering the cm- to sub-mm bands. This facilitates a detailed study of the variability characteristics of an inter- to intra-day variable IDV source from cm- to the short mm-bands. We further aim to constrain the variability brightness temperatures (TB) and Doppler factors (∂) comparing the radio-bands with the hard X-ray emission, as seen by INTEGRAL at 3-200 keV. Results. 0716+714 was in an exceptionally high state and different (slower) phase of short-term variability, when compared to the past, most likely due to a pronounced outburst shortly before the campaign. The flux density variability in the cm- to mm-bands is dominated by a ~4 day time scale amplitude increase of up to ~35{\%}, systematically more pronounced towards shorter wavelengths. The cross-correlation analysis reveals systematic time-lags with the higher frequencies varying earlier, similar to canonical variability on longer time-scales. The increase of the variability amplitudes with frequency contradicts expectations from standard interstellar scintillation (ISS) and suggests a source-intrinsic origin for the observed inter-day variability. We find an inverted synchrotron spectrum peaking near 90 GHz, with the peak flux increasing during the first 4 days. The lower limits to TBderived from the inter-day variations exceed the 1012 K IC-limit by up to 3-4 orders of magnitude. Assuming relativistic boosting, our different estimates of yield robust and self-consistent lower limits of ∂ ≥ 5-33 - in good agreement with ∂VLBIobtained from VLBI studies and the IC-Doppler factors ∂IC > 14-16 obtained from the INTEGRAL data. Conclusions. The non-detection of S5 0716+714 with INTEGRAL in this campaign excludes an excessively high X-ray flux associated with a simultaneous IC catastrophe. Since a strong contribution from ISS can be excluded, we conclude that relativistic Doppler boosting naturally explains the apparent violation of the theoretical limits. All derived Doppler factors are internally consistent, agree with the results from different observations and can be explained within the framework of standard synchrotron-self-Compton (SSC) jet models of AGN.",
keywords = "BL Lacertae objects: general, BL Lacertae objects: individual: S5 0716+71.III, Galaxies: active, Quasars: general, Radiation mechanisms: non-thermal, Radio continuum: galaxies",
author = "L. Fuhrmann and Krichbaum, {T. P.} and A. Witzel and A. Kraus and S. Britzen and S. Bernhart and Impellizzeri, {C. M V} and I. Agudo and J. Klare and Sohn, {B. W.} and E. Angelakis and U. Bach and Gab{\'a}nyi, {K. {\'E}} and E. K{\"o}rding and A. Pagels and Zensus, {J. A.} and Wagner, {S. J.} and L. Ostorero and H. Ungerechts and M. Grewing and M. Tornikoski and Apponi, {A. J.} and B. Vila-Vilar{\'o} and Ziurys, {Lucy M} and Strom, {R. G.}",
year = "2008",
month = "11",
doi = "10.1051/0004-6361:20078893",
language = "English (US)",
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TY - JOUR

T1 - Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71

AU - Fuhrmann, L.

AU - Krichbaum, T. P.

AU - Witzel, A.

AU - Kraus, A.

AU - Britzen, S.

AU - Bernhart, S.

AU - Impellizzeri, C. M V

AU - Agudo, I.

AU - Klare, J.

AU - Sohn, B. W.

AU - Angelakis, E.

AU - Bach, U.

AU - Gabányi, K. É

AU - Körding, E.

AU - Pagels, A.

AU - Zensus, J. A.

AU - Wagner, S. J.

AU - Ostorero, L.

AU - Ungerechts, H.

AU - Grewing, M.

AU - Tornikoski, M.

AU - Apponi, A. J.

AU - Vila-Vilaró, B.

AU - Ziurys, Lucy M

AU - Strom, R. G.

PY - 2008/11

Y1 - 2008/11

N2 - Aims. The BL Lac object S5 0716+71 was observed in a global multi-frequency campaign to search for rapid and correlated flux density variability and signatures of an inverse-Compton (IC) catastrophe during the states of extreme apparent brightness temperatures. Methods. The observing campaign involved simultaneous ground-based monitoring at radio to IR/optical wavelengths and was centered around a 500-ks pointing with the INTEGRAL satellite (November 10-17, 2003). Here, we present the combined analysis and results of the radio observations, covering the cm- to sub-mm bands. This facilitates a detailed study of the variability characteristics of an inter- to intra-day variable IDV source from cm- to the short mm-bands. We further aim to constrain the variability brightness temperatures (TB) and Doppler factors (∂) comparing the radio-bands with the hard X-ray emission, as seen by INTEGRAL at 3-200 keV. Results. 0716+714 was in an exceptionally high state and different (slower) phase of short-term variability, when compared to the past, most likely due to a pronounced outburst shortly before the campaign. The flux density variability in the cm- to mm-bands is dominated by a ~4 day time scale amplitude increase of up to ~35%, systematically more pronounced towards shorter wavelengths. The cross-correlation analysis reveals systematic time-lags with the higher frequencies varying earlier, similar to canonical variability on longer time-scales. The increase of the variability amplitudes with frequency contradicts expectations from standard interstellar scintillation (ISS) and suggests a source-intrinsic origin for the observed inter-day variability. We find an inverted synchrotron spectrum peaking near 90 GHz, with the peak flux increasing during the first 4 days. The lower limits to TBderived from the inter-day variations exceed the 1012 K IC-limit by up to 3-4 orders of magnitude. Assuming relativistic boosting, our different estimates of yield robust and self-consistent lower limits of ∂ ≥ 5-33 - in good agreement with ∂VLBIobtained from VLBI studies and the IC-Doppler factors ∂IC > 14-16 obtained from the INTEGRAL data. Conclusions. The non-detection of S5 0716+714 with INTEGRAL in this campaign excludes an excessively high X-ray flux associated with a simultaneous IC catastrophe. Since a strong contribution from ISS can be excluded, we conclude that relativistic Doppler boosting naturally explains the apparent violation of the theoretical limits. All derived Doppler factors are internally consistent, agree with the results from different observations and can be explained within the framework of standard synchrotron-self-Compton (SSC) jet models of AGN.

AB - Aims. The BL Lac object S5 0716+71 was observed in a global multi-frequency campaign to search for rapid and correlated flux density variability and signatures of an inverse-Compton (IC) catastrophe during the states of extreme apparent brightness temperatures. Methods. The observing campaign involved simultaneous ground-based monitoring at radio to IR/optical wavelengths and was centered around a 500-ks pointing with the INTEGRAL satellite (November 10-17, 2003). Here, we present the combined analysis and results of the radio observations, covering the cm- to sub-mm bands. This facilitates a detailed study of the variability characteristics of an inter- to intra-day variable IDV source from cm- to the short mm-bands. We further aim to constrain the variability brightness temperatures (TB) and Doppler factors (∂) comparing the radio-bands with the hard X-ray emission, as seen by INTEGRAL at 3-200 keV. Results. 0716+714 was in an exceptionally high state and different (slower) phase of short-term variability, when compared to the past, most likely due to a pronounced outburst shortly before the campaign. The flux density variability in the cm- to mm-bands is dominated by a ~4 day time scale amplitude increase of up to ~35%, systematically more pronounced towards shorter wavelengths. The cross-correlation analysis reveals systematic time-lags with the higher frequencies varying earlier, similar to canonical variability on longer time-scales. The increase of the variability amplitudes with frequency contradicts expectations from standard interstellar scintillation (ISS) and suggests a source-intrinsic origin for the observed inter-day variability. We find an inverted synchrotron spectrum peaking near 90 GHz, with the peak flux increasing during the first 4 days. The lower limits to TBderived from the inter-day variations exceed the 1012 K IC-limit by up to 3-4 orders of magnitude. Assuming relativistic boosting, our different estimates of yield robust and self-consistent lower limits of ∂ ≥ 5-33 - in good agreement with ∂VLBIobtained from VLBI studies and the IC-Doppler factors ∂IC > 14-16 obtained from the INTEGRAL data. Conclusions. The non-detection of S5 0716+714 with INTEGRAL in this campaign excludes an excessively high X-ray flux associated with a simultaneous IC catastrophe. Since a strong contribution from ISS can be excluded, we conclude that relativistic Doppler boosting naturally explains the apparent violation of the theoretical limits. All derived Doppler factors are internally consistent, agree with the results from different observations and can be explained within the framework of standard synchrotron-self-Compton (SSC) jet models of AGN.

KW - BL Lacertae objects: general

KW - BL Lacertae objects: individual: S5 0716+71.III

KW - Galaxies: active

KW - Quasars: general

KW - Radiation mechanisms: non-thermal

KW - Radio continuum: galaxies

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