Modelling of Long-Term Afterglow Counterparts to Gravitational Wave Events: The Full View of GRB 170817A

Understand

The arrival of gravitational wave astronomy and a growing number of time-domain focused observatories are set to lead to a increasing number of detections of short gamma-ray bursts (GRBs) launched with a moderate inclination to Earth.

• Being nearby events, these are also prime candidates for very long-term follow-up campaigns and very-long-baseline interferometry (VLBI), which has implications for multi-messenger modelling, data analysis, and statistical inference methods applied to these sources.
• Here we present a comprehensive modelling update that directly incorporates into afterglowpy astrometric observations of the GRB position, Poissonian statistics for faint sources, and modelling of a trans-relativistic population of electrons.
• We use the revolutionary event GW170817 to demonstrate the impact of these extensions both for the best-fit physics parameters and model selection methods that assess the statistical significance of additional late-time emission components.