http://arxiv.org/abs/1808.07887
In anticipation of a LIGO detection of a black hole/neutron star merger, we expand on the intriguing possibility of an electromagnetic counterpart. 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 remark on the fact that a strongly magnetized neutron star companion in such a binary system may thus give rise to a large enough charge on the black hole to allow for potentially observable effects. In turn, a spinning charged black hole itself creates a magnetic field — a black hole pulsar. Another promising signal is provided by the continuous acceleration of charges that we show to be present even when the black hole’s charge has reached its stable value. Additionally, we show that even in a force-free magnetosphere, as in the Blandford-Znajek description, the black hole is in fact charged. This suggests that charged solutions could be important in force-free astrophysical settings, as well as in vacuum.
J. Levin, D. D’Orazio and S. Garcia-Saenz
Mon, 27 Aug 18
1/46
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