How to Measure Black Hole's Mass, Spin and Direction of Spin Axis in Kerr Lens Effect 1: test case with simple source emission near BH

TL;DR

This paper introduces a theoretical method to determine the mass, spin, and spin axis orientation of Kerr black holes by analyzing the time delay and flux ratio of two light rays emitted simultaneously near the black hole.

Contribution

It presents a novel principle for measuring black hole parameters using observable gravitational lensing effects from a single burst emission.

Findings

The method uses time delay and flux ratio of primary and secondary light rays.

Applicable to short, burst-like isotropic emissions near black holes.

Framework can be extended to more complex emission scenarios in future work.

Abstract

We propose a theoretical principle to measure the mass, spin and direction of spin axis of Kerr black holes (BHs) through observing 2 quantities of the spinning strong gravitational lens effect of BHs. Those observable quantities are generated by 2 light rays emitted at the same time by a source near the BH: the primary and secondary rays that reach a distant observer, respectively, the earliest and secondary temporally. The time delay between detection times and the ratio of observed specific fluxes of those rays are the observable quantities. Rigorously, our proposal is applicable to a single burst-like (short duration) isotropic emission by the source. An extension of our principle to cases of complicated emissions may be constructed by summing up appropriately the result of this paper, which will be treated in future works.