Obscured Active Nucleus of NGC 7172 as Seen by NuSTAR
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 ⟨R⟩ = 0.44 and a narrow FeKα line with EW = 67+13-14 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 IFeKα agree best with the scenario of production of the observed FeKα line in a distant gas-dust torus.
- Publication:
-
Kinematics and Physics of Celestial Bodies
- Pub Date:
- November 2018
- DOI:
- 10.3103%2FS0884591318060053
- arXiv:
- arXiv:1808.08457
- Bibcode:
- 2018KPCB...34..302V
- Keywords:
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- active galactic nuclei;
- X-ray emission;
- NGC 7172;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 20 pages, 6 figures, in Russian, accepted for publication in Kin. and Phys. of Celestial Bodies