Can we detect a supertranslated black hole?

TL;DR

This paper investigates whether standard general relativity tests can identify black holes with supertranslation hair by analyzing photon sphere dynamics, aiming to find observational signatures of such exotic black holes.

Contribution

It explores the photon sphere behavior of supertranslated black holes, providing initial insights into their potential observational differences from standard black holes.

Findings

Photon sphere dynamics are complex and may distinguish supertranslated black holes.

First analysis of observational signatures of supertranslation hair on black holes.

Abstract

We attempt to address the question of whether standard tests of general relativity can detect the presence of a black hole carrying a supertranslation field. In this regard, we study the photon sphere of a dynamical black hole carrying a supertranslation hair. We find that the dynamics of the photon sphere is quite subtle and it may offer an opportunity to differentiate a supertranslated black hole from its bald counterpart. This represents a first step towards understanding the observational signatures of a supertranslated dynamical black hole.