Determine whether the prompt radiative efficiency rises with Lorentz factor

Determine whether the prompt radiative efficiency of the GW170817 jet increases with the local Lorentz factor after accounting for the uncertainties in the angular structure and the afterglow-derived kinetic-energy slope.

Background

The paper combines the prompt radiated-energy structure with an independently inferred afterglow kinetic-energy structure to estimate the angular dependence of the prompt radiative efficiency. Fiducial parameter values yield an efficiency proportional to approximately the first power of the Lorentz factor.

However, propagating the allowed uncertainties produces an efficiency exponent ranging from negative to positive values, so the sign of the dependence is not established across the reported parameter ranges.

References

The rise is what the fiducial values give, and it is not established by them .

— The angular structure of the GW170817 jet from prompt emission alone  (2609.04776 - Moradi et al., 4 Sep 2026) in Section “The efficiency” and Supplemental Material, Section “Efficiency”