A universal central engine hypothesis for short and long gamma-ray bursts

It is noted that X-ray tails of short, hard γ-ray bursts (SHBs) are similar to X-ray flashes. We suggest a universal central engine hypothesis, as a way of accounting for this curiosity, in which SHBs differ from long γ-ray bursts in prompt emission because of the differences in the host star and attendant differences in the environment they present to the compact central engine (as opposed to differences in the central engine itself). Observational constraints and implications are discussed.