The NuSTAR view of reflection and absorption in NGC 7582

Creators: Rivers, E.; Baloković, M.; Arévalo, P.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Gandhi, P.; Hailey, C. J.; Harrison, F.; Koss, M.; Ricci, C.; Stern, D.; Walton, D. J.; Zhang, W. W.

Abstract

NGC 7582 is a well-studied X-ray bright Seyfert 2 with moderately heavy N_H ~ 10^(23)-10^(24) cm^(−2), highly variable absorption and strong reflection spectral features. The spectral shape changed around the year 2000, dropping in observed flux and becoming much more highly absorbed. Two scenarios have been put forth to explain this spectral change: (1) the central X-ray source partially "shut off" around this time, decreasing in intrinsic luminosity, with a delayed decrease in reflection features due to the light-crossing time of the Compton-thick material or (2) the source became more heavily obscured, with only a portion of the power law continuum leaking through. NuSTAR observed NGC 7582 twice in 2012, two weeks apart, in order to quantify the reflection using high-quality data above 10 keV. We find that the most plausible scenario is that NGC 7582 has recently become more heavily absorbed by a patchy torus with a covering fraction of ~80%–90% and an equatorial column density of ~ 3 x 10^(24) cm^(−2). We find the need for an additional highly variable full-covering absorber with N_H = (4–6) × 10^(23) cm^(−2) in the line of sight, possibly associated with a hidden broad line region.

Additional Information

© 2015 The American Astronomical Society. Received 2015 July 21; accepted 2015 November 5; published 2015 December 9. We would like to thank the anonymous referee for helpful and constructive comments contributing to this work. This work was supported under NASA Contract No. NNG08FD60C and sub-contract No. 44A-1092750. We have made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). This work has made use of also made use of RXTE and Swift archival data and HEASARC online services, supported by NASA/GSFC, and the NASA/IPAC Extragalactic Database, operated by JPL/California Institute of Technology under contract with NASA. M.B. acknowledges support from NASA Headquarters under the NASA Earth and Space Science Fellowship Program, grant NNX14AQ07H. P.A. acknowledges financial support form Fondecyt grant 1140304. F.E.B. acknowledges support from CONICYT-Chile (Basal-CATA PFB-06/2007, FONDECYT 1141218, "EMBIGGEN" Anillo ACT1101), and the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. M.K. acknowledges support from the Swiss National Science Foundation and Ambizione fellowship grant PZ00P2 154799/1. Facilities: NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, Swift - Swift Gamma-Ray Burst Mission, RXTE - Rossi X-ray Timing Explorer.

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Submitted - 1511.01951v1.pdf

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