A remarkably stable accretion disc in the Seyfert galaxy MCG-5-23-16

Abstract

ABSTRACT MCG-5-23-16 is a Seyfert 1.9 galaxy at redshift z = 0.008 49. We analyse here the X-ray spectra obtained with X-ray Multi-Mirror (XMM)-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) data, which are the first contemporaneous observations with these two X-ray telescopes. Two reflection features, producing a narrow core and a broad component of the Fe Kα, are clearly detected in the data. The analysis of the broad iron line shows evidence of a truncated disc with inner radius $R_{\rm in}=40^{+23}_{-16}$Rg and an inclination of $41^{+9}_{-10}$°. The high quality of the NuSTAR observations allows us to measure a high-energy cut-off at $E_{\rm cut}=131^{+10}_{-9}$ keV. We also analyse the reflection grating spectrometer spectrum, finding that the soft X-ray emission is produced by two photoionized plasma emission regions, with different ionization parameters and similar column densities. Remarkably, the source only shows moderate continuum flux variability, keeping the spectral shape roughly constant in a time-scale of ∼20 yr.