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NuSTAR observations of the Compton-thick active galactic nucleus and ultraluminous x-ray source candidate in NGC 5643

NuSTAR observations of the Compton-thick active galactic nucleus and ultraluminous x-ray source candidate in NGC 5643
NuSTAR observations of the Compton-thick active galactic nucleus and ultraluminous x-ray source candidate in NGC 5643
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 gsim10 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 NH gsim 5 × 1024 cm?2. The range of 2–10 keV absorption-corrected luminosity inferred from the best-fitting models is L2–10,int = (0.8–1.7) × 1042 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.
1538-4357
1-13
Annuar, A.
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Gandhi, P.
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Alexander, D.M.
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Lansbury, G.B.
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Arevalo, P.
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Ballantyne, D.R.
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Balokovic, M.
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Bauer, F.E.
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Boggs, S.E.
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Brandt, W.N.
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Brightman, M.
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Christensen, D.E.
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Craig, W.W.
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Del Moro, A.
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Hailey, C.J.
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Harrison, F.A.
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Hickox, R.C.
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Matt, G.
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Pucetti, S.
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Ricci, C.
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Rigby, J.R.
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Stern, D.
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Walton, D.J.
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Zappacosta, L.
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Zhang, W.
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Annuar, A.
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Gandhi, P.
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Alexander, D.M.
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Lansbury, G.B.
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Arevalo, P.
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Ballantyne, D.R.
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Balokovic, M.
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Bauer, F.E.
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Boggs, S.E.
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Brandt, W.N.
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Brightman, M.
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Christensen, D.E.
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Craig, W.W.
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Del Moro, A.
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Hailey, C.J.
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Harrison, F.A.
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Hickox, R.C.
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Matt, G.
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Pucetti, S.
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Ricci, C.
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Rigby, J.R.
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Stern, D.
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Walton, D.J.
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Zappacosta, L.
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Zhang, W.
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Annuar, A., Gandhi, P., Alexander, D.M., Lansbury, G.B., Arevalo, P., Ballantyne, D.R., Balokovic, M., Bauer, F.E., Boggs, S.E., Brandt, W.N., Brightman, M., Christensen, D.E., Craig, W.W., Del Moro, A., Hailey, C.J., Harrison, F.A., Hickox, R.C., Matt, G., Pucetti, S., Ricci, C., Rigby, J.R., Stern, D., Walton, D.J., Zappacosta, L. and Zhang, W. (2015) NuSTAR observations of the Compton-thick active galactic nucleus and ultraluminous x-ray source candidate in NGC 5643. The Astrophysical Journal, 815 (36), 1-13. (doi:10.1088/0004-637X/815/1/36).

Record type: Article

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 gsim10 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 NH gsim 5 × 1024 cm?2. The range of 2–10 keV absorption-corrected luminosity inferred from the best-fitting models is L2–10,int = (0.8–1.7) × 1042 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.

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Accepted/In Press date: 4 October 2015
Published date: 4 December 2015
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 400036
URI: https://eprints.soton.ac.uk/id/eprint/400036
ISSN: 1538-4357
PURE UUID: e9602a66-7b21-48f5-b51a-fdda38d84947
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 08 Sep 2016 09:01
Last modified: 15 Aug 2019 00:33

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Contributors

Author: A. Annuar
Author: P. Gandhi ORCID iD
Author: D.M. Alexander
Author: G.B. Lansbury
Author: P. Arevalo
Author: D.R. Ballantyne
Author: M. Balokovic
Author: F.E. Bauer
Author: S.E. Boggs
Author: W.N. Brandt
Author: M. Brightman
Author: D.E. Christensen
Author: W.W. Craig
Author: A. Del Moro
Author: C.J. Hailey
Author: F.A. Harrison
Author: R.C. Hickox
Author: G. Matt
Author: S. Pucetti
Author: C. Ricci
Author: J.R. Rigby
Author: D. Stern
Author: D.J. Walton
Author: L. Zappacosta
Author: W. Zhang

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