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

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, F.E.; Craig, W.W.; Del Moro, A.; Hailey, C.J.; Harrison, F.A.; Hickox, R.C.; Matt, G.; Puccetti, S.; Ricci, C.; Rigby, J.R.; Stern, D.; Walton, D.J.; Zappacosta, L.; Zhang, W.

doi:10.1088/0004-637x/815/1/36

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

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, F.E.; Craig, W.W.; Del Moro, A.; Hailey, C.J.; Harrison, F.A.; Hickox, R.C.; Matt, G.; Puccetti, S.; Ricci, C.; Rigby, J.R.; Stern, D.; Walton, D.J.; Zappacosta, L.; Zhang, W.

Authors

A. Annuar

P. Gandhi

Professor David Alexander d.m.alexander@durham.ac.uk
Professor

G.B. Lansbury

P. Arevalo

D.R. Ballantyne

M. Balokovic

F.E. Bauer

S.E. Boggs

W.N. Brandt

M. Brightman

F.E. Christensen

W.W. Craig

A. Del Moro

C.J. Hailey

F.A. Harrison

R.C. Hickox

G. Matt

S. Puccetti

C. Ricci

J.R. Rigby

D. Stern

D.J. Walton

L. Zappacosta

W. Zhang

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.

Citation

Annuar, A., Gandhi, P., Alexander, D., Lansbury, G., Arevalo, P., Ballantyne, D., …Zhang, W. (2015). NuSTAR Observations of the Compton-thick Active Galactic Nucleus and Ultraluminous X-Ray Source Candidate in NGC 5643. Astrophysical Journal, 815(1), Article 36. https://doi.org/10.1088/0004-637x/815/1/36

Journal Article Type	Article
Acceptance Date	Oct 4, 2015
Online Publication Date	Dec 4, 2015
Publication Date	Dec 10, 2015
Deposit Date	May 11, 2016
Publicly Available Date	May 12, 2016
Journal	Astrophysical Journal
Print ISSN	0004-637X
Electronic ISSN	1538-4357
Publisher	American Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	815
Issue	1
Article Number	36
DOI	https://doi.org/10.1088/0004-637x/815/1/36