The Smoking Guns Of Neutron Stars Mergers

The short hard gamma ray burst (SHB) 170817A that followed GW170817A, the first neutron stars merger (NSM) detected in gravitational waves (GWs), has shown beyond doubt that NSMs produce beamed SHBs. Its low luminosity and other properties that differ from those of ordinary SHBs were predicted by the cannonball model of gamma ray bursts. Low luminosity (LL) SHBs are mainly ordinary SHBs viewed far off-axis. They are produced mainly by nearby NSMs. Because of beaming, most of the NSMs, including those within the current horizon of Ligo-Virgo, produce SHBs most of which are invisible from Earth. But, their pulsar wind nebula powered by the spin down of the remnant neutron star produces an early-time isotropic afterglow with a universal temporal shape. This smoking gun of NSMs is detectable independent of whether the SHB was visible, or was invisible from Earth because of being beamed away.