The Profiles of Fe K{\alpha} Line From the Inhomogeneous Accretion Flow

TL;DR

This study models Fe Kα line profiles from inhomogeneous accretion flows around black holes, revealing multi-peak structures influenced by clump properties, which could serve as observable signatures of such clumpy disks.

Contribution

It introduces a ray-tracing method to simulate Fe Kα lines from inhomogeneous accretion flows, highlighting how clump characteristics affect line profiles and potential observability.

Findings

Multi-peak line structures emerge from inhomogeneous accretion flows.

Clump position and size significantly influence line profile features.

High-resolution observations can better constrain clumps around supermassive black holes.

Abstract

The clumpy disc, or inhomogeneous accretion flow, has been proposed to explain the properties of accreting black hole systems. However, the observational evidences remain to be explored. In this work, we calculate the profiles of Fe K{\alpha} lines emitted from the inhomogeneous accretion flow through the ray-tracing technique, in order to find possible observable signals of the clumps. Compared with the skewed doublepeaked profile of the continuous standard accretion disc, the lines show a multi-peak structure when the emissivity index is not very steep. The peaks and wings are affected by the position and size of the cold clumps. When the clump is small and is located in the innermost region, due to the significant gravitational redshift, the blue wing can overlap with the red wing of the outer cold disc/clump, forming a fake peak or greatly enhancing the red peak. Given high enough resolution, it is easier to constrain the clumps around the supermassive black holes than the clumps in stellar mass black holes due to the thermal Doppler effect.