A size-duration trend for gamma-ray burst progenitors

Understand

Gamma-ray bursts (GRBs) show a bimodal distribution of durations, separated at a duration of ~2 s.

• Observations have confirmed the association of long GRBs with the collapse of massive stars.
• The origin of short GRBs is still being explored.
• We examine constraints on the emission region size in short and long GRBs detected by Fermi/GBM.