Black Hole Spin Measurements Based on a Thin Disc Model with Finite Thickness I. An example study of MCG-06-30-15

Abstract

We present a re-analysis of the XMM-Newton and NuSTAR observing campaign for the well-studied, X-ray-bright AGN MCG-06-30-15. In particular, we consider a disc model with finite thickness. By fitting the disc reflection spectra in the data, we obtain a black hole spin of 0.87--0.99 (90\% confidence range) after taking the thickness of the disc into consideration. Spectral models with a grid of mass accretion rate from 0 to $30\%{\dot{M}}_{\mathrm{Edd}}$ are calculated for MCG-06-30-15. This result is obtained by considering a free disc reflection fraction parameter $f_{\mathrm{refl}}$ and is consistent with previous measurements based on razor-thin disc models. Besides, an isotropic, point-like geometry, i.e. the `lamppost' geometry, is assumed for the corona in our model. We find that such a geometry overestimates $f_{\mathrm{refl}}$ in the data. Therefore, thin disc models with consistent `lamppost' values of $f_{\mathrm{refl}}$ provide a worse fit than ones with a free $f_{\mathrm{refl}}$ parameter. We discuss possible reasons for the discrepancy between the observed and theoretical values of $f_{\mathrm{refl}}$ at the end of the paper. Modifications for the over-simplified lamppost model might be needed when the thickness of the thin disc is considered in future work.

15 pages, 14 figures, accepted for publication in MNRAS

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Cited by in corpus (8)

• Testing relativistic reflection models with GRMHD simulations of accreting black holes
• Towards more accurate synthetic reflection spectra: improving the calculations of returning radiation
• Impact of the returning radiation in current tests of the Kerr black hole hypothesis using X-ray reflection spectroscopy
• Impact of the returning radiation on X-ray reflection spectroscopy measurements: the case of Galactic black holes
• On joint analysing XMM-NuSTAR spectra of active galactic nuclei
• Modeling reflection spectra of super-Eddington X-ray sources
• Accretion Geometry of Black Hole X-ray Binaries: Insights from X-ray Observations
• The Effects of Complex Accretion Disk Geometry on Broadened Iron K$\alpha$ Lines