The variable hard X-ray emission of NGC 4945 as observed by NuSTAR.
- Puccetti, S.
- Comastri, A.
- Fiore, F.
- Arévalo, P.
- Risaliti, G.
- Bauer, F.E.
- Brandt, W.N.
- Stern, D.
- Harrison, F.A.
- Alexander, D.M.
- Boggs, S.E.
- Christensen, F.E.
- Craig, W.W.
- Gandhi, P.
- Hailey, C.J.
- Koss, M.J.
- Lansbury, G.B.
- Luo, B.
- Madejski, G.M.
- Matt, G.
- Walton, D.J.
- Zhang, W.
DOIAbstract
We present a broadband (~0.5-79 keV) spectral and temporal analysis of multiple NuSTAR observations combined with archival Suzaku and Chandra data of NGC 4945, the brightest extragalactic source at 100 keV. We observe hard X-ray (>10 keV) flux and spectral variability, with flux variations of a factor of two on timescales of 20 ks. A variable primary continuum dominates the high-energy spectrum (>10 keV) in all states, while the reflected/scattered flux that dominates at E <10 keV stays approximately constant. From modeling the complex reflection/transmission spectrum, we derive a Compton depth along the line of sight of τThomson ~ 2.9, and a global covering factor for the circumnuclear gas of ~0.15. This agrees with the constraints derived...
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