Constraints on black-hole charges with the 2017 EHT observations of M87*

TL;DR

This paper uses EHT observations of M87* to place constraints on the physical charges of various black hole models, ruling out highly charged dilaton black holes and significant parameter regions for doubly-charged black holes.

Contribution

It provides the first observational constraints on the charges of black holes using EHT data, testing specific theoretical models.

Findings

Highly charged dilaton black holes are ruled out for M87*

Significant parameter regions for doubly-charged black holes are excluded

EHT measurements are sufficient to test black hole charge models

Abstract

Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. For example, we show that the quality of the measurements is already sufficient to rule out that M87* is a highly charged dilaton black hole. Similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for the doubly-charged dilaton and the Sen black holes.