Magnetic field and radius of innermost stable circular orbit near SMBH in AGNs

TL;DR

This paper introduces a new method to estimate the magnetic field strength at the innermost stable circular orbit (ISCO) near SMBHs in AGNs using polarimetric observations, confirming magnetic influence on ISCO position.

Contribution

The paper presents a novel approach to measure the magnetic field at ISCO using Faraday rotation effects in polarimetric data, improving understanding of magnetic influence on black hole accretion disks.

Findings

Magnetic fields can shift the ISCO closer to the black hole horizon.

A new method based on polarimetric observations estimates magnetic field strength at ISCO.

Results support the idea that magnetic fields significantly influence ISCO location.

Abstract

Magnetic fields in an accretion disk around the central black hole can modify the position of the innermost stable circular orbit (ISCO) radius and produces the difference for the classical Novikov-Thorne radius. We estimated the ISCO magnetic field strength on the base of polarimetric observations of the accretion disk radiation. This estimate can be obtained with taking into account the effect of Faraday rotation of the polarization plane at the length of the free path of photon between successive electron scattering events. In a result we presented the new method for real estimation of the ISCO radius in the accretion disk, i.e. in the nearest vicinity of a central black hole. Our estimations confirmed the V.P. Frolov, A.A. Shoom and C. Tzounis (2014) conclusion that magnetic field produces the effect in a result of which the innermost stable circular orbit becomes closer to the horizon of a black hole.