# An asymptotically consistent approximant for the equatorial bending angle of light due to Kerr black holes

## TL;DR

This paper introduces a new closed-form approximation for the bending angle of light near Kerr black holes, accurately capturing weak and strong deflection limits and simplifying complex calculations.

## Contribution

It presents an asymptotic approximant that accurately models the bending angle across all impact parameters for Kerr black holes, including extremal spins.

## Key findings

- Accurately predicts light bending angles for Kerr black holes.
- Explicitly satisfies weak and strong deflection limits.
- Reduces computational complexity in black hole simulations.

## Abstract

An accurate closed-form expression is provided to predict the bending angle of light as a function of impact parameter for equatorial orbits around Kerr black holes of arbitrary spin. This expression is constructed by assuring that the weak- and strong-deflection limits are explicitly satisfied while maintaining accuracy at intermediate values of impact parameter via the method of asymptotic approximants (Barlow et al, 2016 Q. J. Mech. Appl. Math., doi=10.1093/qjmam/hbw014). To this end, the strong deflection limit for a prograde orbit around an extremal black hole is examined, and the full non-vanishing asymptotic behavior is determined. The derived approximant may be an attractive alternative to computationally expensive elliptical integrals used in black hole simulations.