出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：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 analysed 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 Xray 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 kTe = 30−50keV to values larger than 100– 150 keV. There is no significant detection of Compton reflection, with a 3s upper limit of R < 0.2, and no line has been detected at 112 keV, as previously claimed from HEAT observations (F112keV < 2.4×10−4 phcm−2 s−1). 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).
