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Big black hole, little neutron star: Magnetic dipole fields in the Rindler spacetime

D'Orazio, Daniel J. and Levin, Janna (2013) Big black hole, little neutron star: Magnetic dipole fields in the Rindler spacetime. Physical Review D, 88 (6). Art. No. 064059 . ISSN 2470-0010. doi:10.1103/PhysRevD.88.064059.

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As a black hole and neutron star approach during inspiral, the field lines of a magnetized neutron star eventually thread the black hole event horizon and a short-lived electromagnetic circuit is established. The black hole acts as a battery that provides power to the circuit, thereby lighting up the pair just before merger. Although originally suggested as an electromagnetic counterpart to gravitational-wave detection, a black hole battery is of more general interest as a novel luminous astrophysical source. To aid in the theoretical understanding, we present analytic solutions for the electromagnetic fields of a magnetic dipole in the presence of an event horizon. In the limit that the neutron star is very close to a Schwarzschild horizon, the Rindler limit, we can solve Maxwell’s equations exactly for a magnetic dipole on an arbitrary worldline. We present these solutions here and investigate a proxy for a small segment of the neutron star orbit around a big black hole. We find that the voltage the black hole battery can provide is in the range ∼10^16 statvolts with a projected luminosity of 10^42  ergs/s for an M=10M_⊙ black hole, a neutron star with a B-field of 10^12  G, and an orbital velocity ∼0.5c at a distance of 3M from the horizon. Larger black holes provide less power for binary separations at a fixed number of gravitational radii. The black hole/neutron star system therefore has a significant power supply to light up various elements in the circuit possibly powering bursts, jets, beamed radiation, or even a hot spot on the neutron star crust.

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Additional Information:© 2013 American Physical Society Received 20 February 2013; published 30 September 2013. We would like to thank Jules Halpern and Sean McWilliams as well as participants of the KITP "Rattle and Shine" conference (July 2012) for useful discussions. This research was supported by a NSF Graduate Research Fellowship Grant No. DGE1144155 (D. J. D.), NSF Grant No. AST-0908365 (J. L.), a KITP Scholarship under Grant No. NSF PHY05-51164 (J. L.), and a Guggenheim Fellowship (J. L.).
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE1144155
NSF KITP ScholarshipPHY05-51164
Guggenheim FellowshipUNSPECIFIED
Issue or Number:6
Classification Code:PACS: 04.70.-s, 04.20.Jb, 04.30.-w, 04.40.Nr
Record Number:CaltechAUTHORS:20131105-095315245
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42248
Deposited On:05 Nov 2013 23:42
Last Modified:10 Nov 2021 16:20

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