Compton processes in the bright AGN MCG+8-11-11

TL;DR

This study analyzes the hard X-ray emission of Seyfert galaxy MCG+8-11-11 using INTEGRAL and SWIFT data, revealing variability in the Comptonising medium's temperature and no significant reflection or line detection.

Contribution

First detailed analysis of MCG+8-11-11's hard X-ray properties with simultaneous INTEGRAL and SWIFT observations, highlighting spectral variability and constraints on reflection and line features.

Findings

High-energy cut-off varies, indicating temperature changes in the Comptonising medium.

No significant Compton reflection detected (R < 0.2).

No line detected at 112 keV, contrary to previous claims.

Abstract

We present preliminary results on the hard X-ray emission properties of the Seyfert 1.5 galaxy MCG+8-11-11 as observed by INTEGRAL and SWIFT. All the INTEGRAL IBIS/ISGRI data available up to October 2009 have been analyzed together with two SWIFT/XRT snapshot observations performed in August and October 2009, quasi-simultaneously to INTEGRAL pointed observations of MCG+8-11-11. No correlation is observed between the hard X-ray flux and the spectral slope, while the position of the high-energy cut-off is found to have varied during the INTEGRAL observations. This points to a change in the temperature of the Comptonising medium from a minimum value of kT = 30-50 keV to values larger than 100-150 keV. There is no significant detection of Compton reflection, with a 3 sigma upper limit of R < 0.2, and no line has been detected at 112 keV, as previously claimed from HEAT observations (112 keV flux F < 2.4e-4 ph/cm^2/s). The variability behaviour of MCG+8-11-11 is found to be similar to that shown by IC 4329A, with different temperatures of the electron plasma for similar flux levels of the source, while other bright Seyfert galaxies present different variability patterns at hard X-rays, with spectral changes correlated to flux variations (e.g. NGC 4151).