On the possible gamma-ray burst -- gravitational wave association in GW150914

TL;DR

This paper explores a theoretical scenario linking the GW150914 black hole merger to a gamma-ray burst, proposing a binary system model where accretion onto the final black hole produces the observed electromagnetic signal.

Contribution

It introduces a novel model connecting black hole mergers with gamma-ray bursts through a binary system involving a massive star and a black hole.

Findings

Recoil velocity of the final black hole could capture surrounding matter.

Gamma-ray burst powered by weak neutrino emission, not Blandford-Znajek.

Model explains low power of observed GRB signal.

Abstract

Data from the Fermi Gamma-ray Burst Monitor satellite observatory suggested that the recently discovered gravitational wave source, a pair of two coalescing black holes, was related to a gamma-ray burst. The observed high-energy electromagnetic radiation (above 50 keV) originated from a weak transient source and lasted for about 1 second. Its localization is consistent with the direction to GW150914. We speculate about the possible scenario for the formation of a gamma-ray burst accompanied by the gravitational-wave signal. Our model invokes a tight binary system consisting of a massive star and a black hole which leads to the triggering of a collapse of the star's nucleus, the formation of a second black hole, and finally to the binary black hole merger. For the most-likely configuration of the binary spin vectors with respect to the orbital angular momentum in the GW150914 event, the recoil speed (kick velocity) acquired by the final black hole through gravitational wave emission is of the order of a few hundred km/s and this might be sufficient to get it closer to the envelope of surrounding material and capture a small fraction of matter from the remnant of the host star. The gamma-ray burst is produced by the accretion of this remnant matter onto the final black hole. The moderate spin of the final black hole suggests that the gamma-ray burst jet is powered by weak neutrino emission rather than the Blandford-Znajek mechanism, and hence explains the low power available for the observed GRB signal.