Conservative limits on the electric charge of Sgr A* in the Reissner-Nordstrom metric

Abstract

In general relativity, the gravitational field of an electrically charged, non-rotating, spherically symmetric body is described by the Reissner-Nordström (RN) metric. Depending on the charge to mass ratio, the solution describes a black hole or a naked singularity. In the naked-singularity regime, a general property of this metric is the existence of a radius, known as the zero-gravity radius, where a test particle would remain at rest. As a consequence of repulsive gravity there is no circular orbit inside this radius, and at least a part of any quasi-stable structure must necessarily lie outside of it. Assuming the iconic torus in the compact source Sgr A* at the Galactic center observed by the Event Horizon Telescope (EHT) to be the image of a quasi-stationary fluid structure, we provide rigorous constraints in the RN metric on the electric charge-to-mass ratio Q/M of Sgr A*. A comparison between the EHT observations and the space-time zero-gravity radius provides the most conservative limit on the charge of Sgr A* to be |Q/M| < 2.32 in geometrized units. A charged naked singularity respecting this charge-to-mass constraint is consistent with the current EHT observations, if the image is not interpreted as a photon ring.

5 pages, 4 figures

References in corpus (11)

• Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits
• Circular motion of neutral test particles in Reissner-Nordström spacetime
• Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign
• Geometric modeling of M87* as a Kerr black hole or a non-Kerr compact object
• Photon rings of spherically symmetric black holes and robust tests of non-Kerr metrics
• An Upper Limit on the Charge of the Black Hole Sgr A* from EHT Observations
• Astrophysical cloaking of a naked singularity

Cited by in corpus (2)

• Testing black hole space-times with the S2 star orbit: a Bayesian comparison
• Photon Ring Dimming as a Signature of Photon-Axion Conversion in Janis-Newman-Winicour Naked Singularity