期刊
ASTROPHYSICAL JOURNAL
卷 666, 期 1, 页码 122-127出版社
IOP PUBLISHING LTD
DOI: 10.1086/519486
关键词
galaxies : active; galaxies : individual ( NGC 2992, NGC 3081); galaxies : Seyfert; X-rays : galaxies
The Seyfert 2 galaxies NGC 2992 and NGC 3081 have been observed by INTEGRAL and Swift. We report the results and a comparison of the spectrum above 10 keV based on INTEGRAL IBIS/ISGRI, Swift/BAT, and BeppoSAX/PDS. A spectrum can be extracted in the X-ray energy band ranging from 1 up to 200 keV. Although NGC 2992 shows a complex spectrum below 10 keV, the hard tail observed by various missions exhibits a slope of Gamma = 2, independent of the flux level during the observation. No cut-off is detectable up to the detection limit around 200 keV. In addition, NGC 3081 is detected in the INTEGRAL and Swift observation and also shows an unbroken Gamma = 1: 8 spectrum upto 150 keV. These two Seyfert galaxies give further evidence that a high-energy cut-off in the hard X-ray spectra is often located at energies E-C >> 100 keV. In NGC 2992 a constant spectral shape is observed over a hard X-ray luminosity variation by a factor of 11. This might indicate that the physical conditions of the emitting hot plasma are constant, while the amount of plasma varies, due to long-term flaring activity.
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