Description
Long GRBs are traditionally thought to come from collapsing stars and short GRBs to originate from binary neutron star mergers. However, the discoveries of kilonovae coincident with GRB 211211A and GRB 230307A provide conclusive evidence that some long GRBs can in fact originate from BNS mergers. These long merger GRBs can in part be classified by the existence of an extended plateau of emission after the initial prompt spike in their lightcurves, termed extended emission. The source of this extended emission is still debated. In this talk I will present a shell model that utilises high latitude emission and frame propagation effects to produce extended emission-like lightcurves. Our results show that the timescales of these long mergers can be reproduced through geometrical and frame transformation effects only, without the need for an additional source of energy injection. I will show that our model is capable of producing the broad features of extended emission including spectral evolution such as that seen in GRB 211211A (Gompertz et al, 2022).
