NuSTAR catches the unveiling nucleus of NGC 1068

Creators: Marinucci, A.; Bianchi, S.; Matt, G.; Alexander, D. M.; Baloković, M.; Bauer, F. E.; Brandt, W. N.; Gandhi, P.; Guainazzi, M.; Harrison, F. A.; Iwasawa, K.; Koss, M.; Madsen, K. K.; Nicastro, F.; Puccetti, S.; Ricci, C.; Stern, D.; Walton, D. J.

Abstract

We present a NuSTAR and XMM–Newton monitoring campaign in 2014/2015 of the Compton-thick Seyfert 2 galaxy, NGC 1068. During the 2014 August observation, we detect with NuSTAR a flux excess above 20 keV (32 ± 6 per cent) with respect to the 2012 December observation and to a later observation performed in 2015 February. We do not detect any spectral variation below 10 keV in the XMM–Newton data. The transient excess can be explained by a temporary decrease of the column density of the obscuring material along the line of sight (from N_H ≃ 10^(25) cm^(−2) to N_H = 6.7 ± 1.0 × 10^(24) cm^(−2)), which allows us for the first time to unveil the direct nuclear radiation of the buried active galactic nucleus in NGC 1068 and to infer an intrinsic 2–10 keV luminosity L_X = 7^(+7)_(−4) × 10^(43) erg s^(−1).

Additional Information

© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 November 10. Received 2015 October 29. In original form 2015 July 16. First published online December 17, 2015. We thank the referee for her/his comments. AM, SB and GM acknowledge financial support from Italian Space Agency under grant ASI/INAF I/037/12/0-011/13. FEB acknowledges support from CONICYT-Chile (PFB-06/2007, FONDECYT 1141218, ACT1101), and grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. WNB acknowledges Caltech NuSTAR subcontract 44A-1092750. PG thanks STFC for support (grant reference ST/J003697/1). This work was supported under NASA Contracts No. NNG08FD60C, NNX10AC99G, NNX14AQ07H and 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).

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Published - MNRAS-2016-Marinucci-L94-8.pdf

Submitted - 1511.03503v1.pdf

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