Constraining the charge of the Galactic centre black hole

authored by

Michal Zajaček, Arman Tursunov, Andreas Eckart, Silke Britzen, Eva Hackmann, Vladimír Karas, Zdeněk Stuchlík, Bozena Czerny, J. Anton Zensus

Abstract

In this contribution, we summarize our results concerning the observational constraints on the electric charge associated with the Galactic centre black hole - Sgr A∗. According to the no-hair theorem, every astrophysical black hole, including supermassive black holes, is characterized by at most three classical, externally observable parameters - mass, spin, and the electric charge. While the mass and the spin have routinely been measured by several methods, the electric charge has usually been neglected, based on the arguments of efficient discharge in astrophysical plasmas. From a theoretical point of view, the black hole can attain charge due to the mass imbalance between protons and electrons in fully ionized plasmas, which yields about ∼ 10⁸ C for Sgr A∗. The second, induction mechanism concerns rotating Kerr black holes embedded in an external magnetic field, which leads to electric field generation due to the twisting of magnetic field lines. This electric field can be associated with the induced Wald charge, for which we calculate the upper limit of ∼ 10¹⁵ C for Sgr A∗. Although the maximum theoretical limit of ∼ 10¹⁵ C is still 12 orders of magnitude smaller than the extremal charge of Sgr A∗, we analyse a few astrophysical consequences of having a black hole with a small charge in the Galactic centre. Two most prominent ones are the effect on the X-ray bremsstrahlung profile and the effect on the position of the innermost stable circular orbit.

External Organisation(s)

Max Planck Institute for Radio Astronomy (MPIfR)
University of Cologne
Silesian University in Opava
Czech Academy of Sciences (CAS)
Center of Applied Space Technology and Microgravity (ZARM)
Polish Academy of Sciences (PASIFIC)

Type

Conference article

Journal

Journal of Physics: Conference Series

Volume

1258

No. of pages

17

ISSN

1742-6588

Publication date

21.10.2019

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Physics and Astronomy(all)

Electronic version(s)

https://doi.org/10.48550/arXiv.1812.03574 (Access: Open)
https://doi.org/10.1088/1742-6596/1258/1/012031 (Access: Open)