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

TL;DR

This study presents the first simultaneous X-ray observations of the Seyfert galaxy MCG-5-23-16, revealing a stable accretion disc with a truncated inner radius, consistent spectral shape over two decades, and detailed reflection features.

Contribution

It provides the first contemporaneous XMM-Newton and NuSTAR data analysis of MCG-5-23-16, showing a remarkably stable accretion disc and detailed reflection and ionisation features.

Findings

Detection of both narrow and broad Fe Kα reflection features.

Evidence for a truncated accretion disc with inner radius ~40 Rg.

Spectral shape remains stable over ~20 years despite moderate flux variability.

Abstract

MCG-5-23-16 is a Seyfert 1.9 galaxy at redshift z=0.00849. We analyse here the X-ray spectra obtained with XMM-Newton and 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 K$\alpha$, are clearly detected in the data. The analysis of the broad iron line shows evidence of a truncated disc with inner radius $R_{\rm in}=40^{+23}_{-16}$ $R_g$ and an inclination of $41^{+9}_{-10}$ $^\circ$. 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 RGS spectrum, finding that the soft X-ray emission is produced by two photoionised plasma emission regions, with different ionisation 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 $\sim20$ years.