Afterglows and Kilonovae Associated with Nearby Low-Luminosity Short-Duration Gamma-Ray Bursts: Application to GW170817/GRB170817A

TL;DR

This paper models the multi-wavelength afterglow and kilonova signals of GW170817/GRB170817A to determine the jet structure and intrinsic energy, providing insights into low-luminosity short gamma-ray bursts.

Contribution

It introduces a comparative modeling approach for different jet structures and ejecta properties to interpret the afterglow and kilonova observations of GW170817/GRB170817A.

Findings

Structured jet model fits observed afterglow data.

Ejecta mass and velocity constraints are derived.

Distinguishes between jet configurations based on multi-wavelength data.

Abstract

Very recently, the gravitational-wave (GW) event GW170817 was discovered to be associated with the short gamma-ray burst (GRB) 170817A. Multi-wavelength follow-up observations were carried out, and X-ray, optical, and radio counterparts to GW170817 were detected. The observations undoubtedly indicate that GRB 170817A originates from a binary neutron star merger. However, the GRB falls into the low-luminosity class that could have a higher statistical occurrence rate and detection probability than the normal (high-luminosity) class. This implies the possibility that GRB 170817A is intrinsically powerful, but we are off-axis and only observe its side emission. In this Letter, we provide a timely modeling of the multi-wavelength afterglow emission from this GRB and the associated kilonova signal from the merger ejecta, under the assumption of a structured jet, a two-component jet, and an intrinsically less-energetic quasi-isotropic fireball, respectively. Comparing the afterglow properties with the multi-wavelength follow-up observations, we can distinguish between these three models. Furthermore, a few model parameters (e.g., the ejecta mass and velocity) can be constrained.