The obscured active nucleus of NGC 7172 as seen BY NuSTAR

1Vasylenko, AA
1Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2018, 34(6):41-56
Start Page: Extragalactic Astronomy
Language: Russian
Abstract: 

We analyse the properties of the X-ray emission from Seyfert 2 NGC 7172 which are based on the 32 ks observational data from NuSTAR in 2014. This source showed a constant Compton-thin obscuration NH ≈ 8-1022-2, which is similar to that observed by XMM-Newton, Suzaku, ASCA and BeppoSAX over past 30 years. We revealed the presence of a moderate reflection component with = 0.44 and a narrow Fe Kα line with EW = 67 +13-14 eV. The applied numerical models of torus confirmed the Compton-thin type of the Seyfert nucleus and allowed us to obtain an estimate of the torus opening angle Θi ≈ 59° and inclination Θi ≈ 61°. Using the observation data of previous observation, we demonstrate also the long-term variability of intrinsic luminosity Lintr(2—10 keV) almost by order and EWFeKα by factor ~4 on a timescale of ~12 years, that coincides to the distance of d ≈ 3.7 pc between central source and reprocessing medium. Such changes of intrinsic luminosity without changes in NH value indicate the variability ofa central source. In the same time the spectral analysis results with the presence of the lag between variability of intrinsic luminosity Lintr(2—10 keV) and EWFeKα,as well as a behavior of intensity IFeKα of the line are in agreement with the scenario, where observed FeKα line is generated in a distant gas-dust torus.

Keywords: active galactic nuclei, NGC 7172, X-rays
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