It has been suggested that short gamma ray bursts (GRBs) have shorter or undetectable spectral lags than long GRB because in the former, the observer's line of sight makes a larger angle with the GRB jet axis than for the latter. It is proposed that simultaneous gravitational wave - short GRB events could provide a simple test of this hypothesis. Multimessenger astronomy eventually may test whether event horizons are a necessary ingredient for GRB.
@article{arxiv.1710.05688,
title = {Testing the Viewing Angle Hypothesis for Short GRB with LIGO events},
author = {David Eichler},
journal= {arXiv preprint arXiv:1710.05688},
year = {2017}
}