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Durham University

Department of Physics

Staff profile

Publication details for Prof David Alexander

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. (2016). NuSTAR catches the unveiling nucleus of NGC 1068. Monthly Notices of the Royal Astronomical Society Letters 456(1): L94-L98.

Author(s) from Durham

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 NH ≃ 1025 cm−2 to NH = 6.7 ± 1.0 × 1024 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 LX=7+7−4×1043X=7−4+7×1043 erg s−1.