Multi-messenger Extended Emission from the Compact Remnant in GW170817

GW170817/GRB 170817A probably marks a double neutron star (NS) coalescence. Extended emission s post-merger shows an estimated energy output determined by response curves to power-law signal injections, where c is the velocity of light. It provides calorimetric evidence for a rotating black hole of , inheriting the angular momentum J of the merged hyper-massive NS in the immediate aftermath of GW170817 following core-collapse about or prior to t _s. Core-collapse greatly increases the central energy reservoir to , accounting for even at modest efficiencies in radiating gravitational waves through a non-axisymmetric thick torus. The associated multi-messenger output in ultra-relativistic outflows and sub-relativistic mass-ejecta is consistent with observational constraints from the gamma-ray burst afterglow emission of GRB 170817A and accompanying kilonova.