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Published December 10, 2015 | Submitted + Published
Journal Article Open

NuSTAR Observations of the Compton-thick Active Galactic Nucleus and Ultraluminous X-ray Source Candidate in NGC 5643

Abstract

We present two Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the local Seyfert 2 active galactic nucleus (AGN) and an ultraluminous X-ray source (ULX) candidate in NGC 5643. Together with archival data from Chandra, XMM-Newton, and Swift-BAT, we perform a high-quality broadband spectral analysis of the AGN over two decades in energy (~0.5–100 keV). Previous X-ray observations suggested that the AGN is obscured by a Compton-thick (CT) column of obscuring gas along our line of sight. However, the lack of high-quality ≳10 keV observations, together with the presence of a nearby X-ray luminous source, NGC 5643 X–1, have left significant uncertainties in the characterization of the nuclear spectrum. NuSTAR now enables the AGN and NGC 5643 X–1 to be separately resolved above 10 keV for the first time and allows a direct measurement of the absorbing column density toward the nucleus. The new data show that the nucleus is indeed obscured by a CT column of N_H ≳ 5 × 10^(24) cm^(−2). The range of 2–10 keV absorption-corrected luminosity inferred from the best-fitting models is L_(2–10,int) = (0.8–1.7) × 10^(42) erg s^(−1), consistent with that predicted from multiwavelength intrinsic luminosity indicators. In addition, we also study the NuSTAR data for NGC 5643 X–1 and show that it exhibits evidence of a spectral cutoff at energy E ~ 10 keV, similar to that seen in other ULXs observed by NuSTAR. Along with the evidence for significant X-ray luminosity variations in the 3–8 keV band from 2003 to 2014, our results further strengthen the ULX classification of NGC 5643 X–1.

Additional Information

© 2015 The American Astronomical Society. Received 2015 June 2; accepted 2015 October 4; published 2015 December 4. The authors thank the anonymous referee for useful comments that have helped to improve the paper. We thank Chris Done for some discussions on the residuals around the iron line complex. A.A. thanks Wasutep Luangtip for useful discussion on NGC 5643 X–1 and help with the MARX simulation. We also thank Neil Gehrels and the Swift team for the simultaneous Swift-XRT observation. We acknowledge financial support from Majlis Amanah Rakyat (MARA) Malaysia (A.A.), the Science and Technology Facilities Council (STFC) grants ST/J003697/1 (P.G.), ST/I0015731/1 (D.M.A. and A.D.M.), and ST/K501979/1 (G.B.L.), the Leverhulme Trust (D.M.A.), NASA Headquarters under the NASA Earth and Space Science Fellowship Program grant NNX14AQ07H (M.B.), CONICYT-Chile grants Basal-CATA PFB-06/2007 (F.E.B.), FONDECYT 1141218 (F.E.B.), and "EMBIGGEN" Anillo ACT1101 (F.E.B.); the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS (F.E.B.). NuSTAR is a project led by the California Institute of Technology (Caltech), managed by the Jet Propulsion Laboratory (JPL), and funded by the National Aeronautics and Space Administration (NASA). We thank the NuSTAR Operations, Software and Calibrations teams for support with 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), and the XRT Data Analysis Software (xrt-das). This research also made use of the data obtained through the High Energy Astrophysics Science Archive Research Center (HEASARC) Online Service, provided by the NASA/Goddard Space Flight Center, and the NASA/IPAC extragalactic Database (NED) operated by JPL, Caltech under contract with NASA. Facilities: NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, XMM - Newton X-Ray Multimirror Mission satellite, CXO - , Swift - Swift Gamma-Ray Burst Mission.

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Published - Annuar_2015.pdf

Submitted - 1509.03322v1.pdf

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Additional details

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August 22, 2023
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