van Putten, Maurice H. P. M.Maurice H. P. M.van PuttenDELLA VALLE, MassimoMassimoDELLA VALLELevinson, AmirAmirLevinson2022-03-242022-03-2420192041-8205http://hdl.handle.net/20.500.12386/31852GW170817/GRB 170817A probably marks a double neutron star (NS) coalescence. Extended emission {t}<SUB>s</SUB>≃ (0.67+/- 0.03) s post-merger shows an estimated energy output { \mathcal E }≃ (3.5+/- 1) % {M}<SUB>☉ </SUB>{c}<SUP>2</SUP> 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 ∼ 3{M}<SUB>☉ </SUB>, 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 <SUB> s </SUB>. Core-collapse greatly increases the central energy reservoir to {E}<SUB>J</SUB>≲ 1{M}<SUB>☉ </SUB>{c}<SUP>2</SUP>, accounting for { \mathcal E } 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.STAMPAenArticle10.3847/2041-8213/ab18a22-s2.0-85067130601https://iopscience.iop.org/article/10.3847/2041-8213/ab18a22019ApJ...876L...2VFIS/05 - ASTRONOMIA E ASTROFISICA