Possible role of magnetic reconnection in the electromagnetic counterpart of binary black hole merger

Abstract: We propose a qualitative scenario to interpret the argued association between the direct measurement of the gravitational wave event GW150914 by Laser Interferometer Gravitational Wave Observatory (LIGO)-Virgo collaborations and the hard $X$-ray transient detected by Fermi-Gamma-ray Burst Monitor (GBM) $0.4$ sec after. In a binary system of two gravitationally collapsing objects with a non-vanishing electric charge, the compenetration of the two magnetospheres occurring during the coalescence, through magnetic reconnection, produces a highly collimated relativistic outflow that becomes optically thin and shines in the GBM field of view. We propose that this process should be expected as a commonplace in the future joint gravitational/electromagnetic detections and, in case of neutron star-neutron star merger event, might lead to detectable $X$- or $\gamma$-ray precursors to, or transients associated with, the gravitational bursts.