Variations of the X-ray spectrum of AGN NGC 4945 from the data of INTEGRAL space mission
|1Fedorova, EV, 1Zhdanov, VI |
1Astronomical Observatory of Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
|Kinemat. fiz. nebesnyh tel (Online) 2016, 32(4):23-35|
|Start Page: Extragalactic Astronomy|
The results of the 3...500 keV 11-year INTEGRAL monitoring of NGC 4945 are treated. To analyze them we applied a two-component spectral model, consisting of a direct nuclear emission absorbed in the compton-thick circumnuclear torus and a reprocessed one, reflected from inner torus walls. Parameters of full-time exposure spectrum are: photon index =1.6 ± 0.07, high-energy cut-off E c=1572922 keV, column density of absorbing medium N H, 1 = 5.0 1.00.9 1024 cm–2 for the direct emission and two orders lower for the reprocessed one. Both the X-ray flux and spectral shape of NGC 4945 vary. The spectral shape changes can be caused by inhomogeneities of the absorbing medium surrounding the nucleus. But in the same time there are some signs of moderate variations in high-energy range, inflicted by changes of physical conditions in the “central engine”.
|Keywords: INTEGRAL space mission, NGC 4945, X-ray spectrum, “central engine”|
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