Kinematics and Physics of Celestial Bodies

, Volume 34, Issue 6, pp 302–312 | Cite as

Obscured Active Nucleus of NGC 7172 as Seen by NuSTAR

  • A. A. VasylenkoEmail author

Abstract—The properties of X-ray emission of the active nucleus of the Seyfert 2 galaxy NGC 7172 detected by the NuSTAR space observatory in 2014 are analyzed. This source exhibits constant obscuration NH ≈ 8 × 1022 cm–2, which is similar to that determined by XMM-Newton, Suzaku, ASCA, and BeppoSAX in the past 30 years. Spectral analysis reveals the presence of a moderate reflection component with \(\left\langle R \right\rangle \) = 0.44 and a narrow FeKα line with EW = \(67_{{ - 14}}^{{ + 13}}\) eV. Numerical torus models confirm that the Seyfert nucleus of NGC 7172 is of a Compton-thin type and provide estimates of the torus inclination (Θi ≈ 61° and its opening angle (Θt ≈ 59°). The data of earlier observations reveal approximately order-of-magnitude variations of intrinsic luminosity Lintr(2–10 keV) and fourfold variations of equivalent width EW FeKα on a timescale of 12 years, which corresponds to distance d ≈ 3.7 pc. This behavior of Lintr(2–10 keV) is indicative of variability of the central source. The results of spectral analysis, the lag between variations of the intrinsic luminosity and EWFeKα, and the variation of intensity \({{I}_{{{\text{Fe}}{{K}_{\alpha }}}}}\) agree best with the scenario of production of the observed FeKα line in a distant gas-dust torus.

Keywords: active galactic nuclei X-ray emission NGC 7172 



Data from the NuSTAR mission, which is a project headed by the California Institute of Technology, developed at the Jet Propulsion Laboratory, and financed by NASA, and the NuSTAR (NuSTARDAS) data processing software, which was developed by a collaboration of researchers from the ASI Science Data Center (Italy) and the California Institute of Technology, were used in this study. It was supported in part by a research grant for young scientists from the National Academy of Sciences of Ukraine (project no. 389Kt of the Main Astronomical Observatory).


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Copyright information

© Allerton Press, Inc. 2018

Authors and Affiliations

  1. 1.Main Astronomical Observatory, National Academy of Sciences of UkraineKyivUkraine

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