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High Energy Break and Reflection Features in the Seyfert Galaxy MCG+8-11-11

P. Grandi·F. Haardt·G. Ghisellini·E. J. Grove·L. Maraschi·C. M. Urry
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Abstract

We present the results from ASCA and OSSE simultaneous observations of the Seyfert 1.5 galaxy MCG+8-11-11 performed in August-September 1995. The ASCA observations indicate a modest flux increase (20%) in 3 days, possibly correlated to a softening of the 0.6-9 keV spectrum. The spectrum is well described by a hard power law (Gamma=1.64) absorbed by a column density slightly larger than the Galactic value, with an iron line at 6.4 keV of EW=400 eV. The simultaneous OSSE data are characterized by a much softer power law with photon index Gamma=3.0, strongly suggesting the presence of a spectral break in the hard X/soft gamma-ray band. A joint fit to OSSE and ASCA data clearly shows an exponential cut-off at about 300 keV, and strong reflection component. MCG+8-11-11 features a spectral break in the underlying continuum unambiguously. This, together with the inferred low compactness of this source, favours thermal or quasi-thermal electron Comptonization in a structured Corona as the leading process of high energy radiation production.

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P. Grandi, F. Haardt, G. Ghisellini, E. J. Grove, L. Maraschi, C. M. Urry. 1997-11-20. High Energy Break and Reflection Features in the Seyfert Galaxy MCG+8-11-11. https://doi.org/10.1086/305557

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