Schematic of event timing in the first double neutron star merger detected (top): the multimessenger event GW170817 at merger time t_m with accompanying GRB170817A at t_GRB = t_m + t_g following a gap t_g ≃ 1.7 s (bottom). The central engine of GRB170817A formed in this gap by causality, whereby t_m < t_s < t_GRB for the start-time of accompanying gravitational radiation. This gap condition poses a discrete event time problem for the probability p of false alarm (PFA) for a candidate detection to be in the 1.7 s gap between GW1709817–GRB170817A: p = t_g/T marked by the (unique) global maximum of an indicator function over an observational time T given the uniform prior on astrophysical event times (Appendix A). When sufficiently large, the energy output ℰ_GW marked by t_s can break the degeneracy between neutron stars and black holes.