Short gamma-ray bursts in the "time-reversal" scenario

摘要: Short gamma-ray bursts (SGRBs) are among the most luminous explosions in Universe and their origin still remains uncertain. Observational evidence favors association with binary neutron star or star-black hole (NS-BH) mergers. Leading models relate SGRBs to a relativistic jet launched by BH-torus system resulting from merger. However, recent observations have revealed large fraction of SGRB events accompanied X-ray afterglows durations $\sim10^2\!-\!10^5~\mathrm{s}$, suggesting continuous energy injection long-lived central engine, which is incompatible short ($\lesssim1~\mathrm{s}$) accretion timescale system. The formation supramassive NS, resisting collapse on much longer spin-down timescales, can explain these afterglow durations, but leaves serious doubts whether be at Here we present novel scenario accommodating both aspects, where produced after NS. Early differential rotation subsequent emission generate an optically thick environment around NS consisting photon-pair nebula outer shell baryon-loaded ejecta. While easily drills through this environment, radiation diffuses outwards timescales accumulates delay that allows observed before (part of) long-lasting signal. By analyzing diffusion for wide range physical parameters, find delays generally reach $\sim10^5~\mathrm{s}$, compatible observations. success fundamental test makes "time-reversal" attractive alternative current models.