Black Hole Pulsar

TL;DR

This paper explores how a spinning, charged black hole in a neutron star merger can generate observable electromagnetic signals, including pulsar-like emissions, expanding the potential for detecting such events.

Contribution

It introduces the idea that black hole charge, acquired via the Wald mechanism, can produce observable electromagnetic effects, including black hole pulsar phenomena.

Findings

Charged black holes can produce detectable electromagnetic radiation.

Spinning black holes can act as pulsars due to their magnetic dipole.

Charge flux contributes to the luminosity in black hole/neutron star systems.

Abstract

In anticipation of a LIGO detection of a black hole/neutron star merger, we expand on the intriguing possibility of an electromagnetic counterpart. Black hole/Neutron star mergers could be disappointingly dark since most black holes will be large enough to swallow a neutron star whole, without tidal disruption and without the subsequent fireworks. Encouragingly, we previously found a promising source of luminosity since the black hole and the highly-magnetized neutron star establish an electronic circuit -- a black hole battery. In this paper, arguing against common lore, we consider the electric charge of the black hole as an overlooked source of electromagnetic radiation. Relying on the well known Wald mechanism by which a spinning black hole immersed in an external magnetic field acquires a stable net charge, we show that a strongly-magnetized neutron star in such a binary system will give rise to a large enough charge in the black hole to allow for potentially observable effects. Although the maximum charge is stable, we show there is a continuous flux of charges contributing to the luminosity. Most interestingly, the spinning charged black hole then creates its own magnetic dipole to power a black hole pulsar.