Measuring key X‐ray parameters from simulated spectra of Seyfert galaxies

Supermassive black hole (SMBH) accretion is an important topic of astro‐physical research for a variety of fields. However, literature shows that precisely modelling the X‐ray reflection component of an accretion disk around a SMBH is challenging. We test how reliably we can measure key active galactic nuclei (AGN) X‐ray reflection parameters by simulating the spectra of average Seyfert 1 galaxies and then fitting those spectra using common modelling techniques. The AGN spectra were created from 0.01–300.0 keV using XMM‐ Newton pn responses and with (3.75±0.10)×10 6 counts in the 2–10 keV band. The model RELXILL was used to create all spectra with a reflection fraction (ratio of reflected flux over primary flux from 0.1–100 keV) of R = 1. The values of six key parameters were generated randomly within given ranges to simulate the spectra: photon index (Γ), inner emissivity index ( q 1), black hole spin ( a ), disk inclination angle (θ), ionization (ξ), and iron abundance in solar units ( A F e ). Once the simulated spectra were created, they were autonomously fit with RELXILL from 2.5–10.0 keV. All six key parameters were allowed to vary throughout the modelling process, with a gradual thawing of model parameters to mimic manual fitting procedure. We find that we can successfully measure key AGN spectral components in this scenario, but some conditions apply: Γ, θ, and A Fe are well constrained, however they are also consistently overestimated. Only black hole spin ( a ) measurements that are in extrema, a > 0.9, can be considered reliable. Lastly, ξ and q 1 cannot be measured and these parameters – along with intermediate spin values – should be verified using other techniques. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)