High-energy monitoring of NGC 4593 with XMM–Newton and NuSTAR. X-ray spectral analysis

• Published in: Monthly notices of the Royal Astronomical Society 2016-11, Vol.463 (1), p.382-392
• Main Authors: Ursini, F., Petrucci, P.-O., Matt, G., Bianchi, S., Cappi, M., De Marco, B., De Rosa, A., Malzac, J., Marinucci, A., Ponti, G., Tortosa, A.
• Format: Article
• Language: English
• Subjects: Astrophysics; Constants; Correlation analysis; Emissions; Galaxies; Luminosity; Monitoring; Optics; Physics; Power law; Reflection; Seyfert galaxies; Spectra; Spectrum analysis; Star & galaxy formation; XMM (spacecraft)
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw2022

We present results from a joint XMM–Newton/NuSTAR monitoring of the Seyfert 1 NGC 4593, consisting of 5 × 20 ks simultaneous observations spaced by 2 d, performed in 2015 January. The source is variable, both in flux and spectral shape, on time-scales down to a few ks and with a clear softer-when-brighter behaviour. In agreement with past observations, we find the presence of a warm absorber well described by a two-phase ionized outflow. The source exhibits a cold, narrow and constant Fe Kα line at 6.4 keV, and a broad component is also detected. The broad-band (0.3–79 keV) spectrum is well described by a primary power law with Γ ≃ 1.6–1.8 and an exponential cut-off varying from $90^{+ 40}_{- 20}$ to >700 keV, two distinct reflection components, and a variable soft excess correlated with the primary power law. This campaign shows that probing the variability of Seyfert 1 galaxies on different time-scales is of prime importance to investigate the high-energy emission of active galactic nuclei.