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IC 3639 - A new bona fide Compton-thick AGN unveiled by NuSTAR

Boorman, P.G.; Gandhi, P.; Alexander, D.M.; Annuar, A.; Ballantyne, D.R.; Bauer, F.; Boggs, S.E.; Brandt, W.N.; Brightman, M.; Christensen, F.E.; Craig, W.W.; Farrah, D.; Hailey, C.J.; Harrison, F.A.; Hönig, S.F.; Koss, M.J.; LaMassa, S.M.; Massini, A.; Ricci, C.; Risaliti, G.; Stern, D.; Zhang, W.

IC 3639 - A new bona fide Compton-thick AGN unveiled by NuSTAR Thumbnail


P.G. Boorman

P. Gandhi

A. Annuar

D.R. Ballantyne

F. Bauer

S.E. Boggs

W.N. Brandt

M. Brightman

F.E. Christensen

W.W. Craig

D. Farrah

C.J. Hailey

F.A. Harrison

S.F. Hönig

M.J. Koss

S.M. LaMassa

A. Massini

C. Ricci

G. Risaliti

D. Stern

W. Zhang


We analyze high-quality NuSTAR observations of the local (z = 0.011) Seyfert 2 active galactic nucleus (AGN) IC 3639, in conjunction with archival Suzaku and Chandra data. This provides the first broadband X-ray spectral analysis of the source, spanning nearly two decades in energy (0.5–30 keV). Previous X-ray observations of the source below 10 keV indicated strong reflection/obscuration on the basis of a pronounced iron fluorescence line at 6.4 keV. The hard X-ray energy coverage of NuSTAR, together with self-consistent toroidal reprocessing models, enables direct broadband constraints on the obscuring column density of the source. We find the source to be heavily Compton-thick (CTK) with an obscuring column in excess of 3.6 10 ´ 24 cm−2 , unconstrained at the upper end. We further find an intrinsic 2–10 keV luminosity of - = - + log erg s 43.4 L 10 2 10 keV 1 1.1 0.6 ( [ ]) – to 90% confidence, almost 400 times the observed flux, and consistent with various multiwavelength diagnostics. Such a high ratio of intrinsic to observed flux, in addition to an Fe-Kα fluorescence line equivalent width exceeding 2 keV, is extreme among known bona fide CTK AGNs, which we suggest are both due to the high level of obscuration present around IC 3639. Our study demonstrates that broadband spectroscopic modeling with NuSTAR enables large corrections for obscuration to be carried out robustly and emphasizes the need for improved modeling of AGN tori showing intense iron fluorescence.


Boorman, P., Gandhi, P., Alexander, D., Annuar, A., Ballantyne, D., Bauer, F., …Zhang, W. (2016). IC 3639 - A new bona fide Compton-thick AGN unveiled by NuSTAR. Astrophysical Journal, 833(2), 245-262.

Journal Article Type Article
Acceptance Date Oct 26, 2016
Online Publication Date Dec 20, 2016
Publication Date Dec 20, 2016
Deposit Date Jan 20, 2017
Publicly Available Date Jan 26, 2017
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 833
Issue 2
Article Number 245
Pages 245-262
Public URL
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Published Journal Article (2.4 Mb)

Copyright Statement
© 2016. The American Astronomical Society. All rights reserved.

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