http://arxiv.org/abs/1710.05857
{\it Fermi}/GBM (Gamma-ray Burst Monitor) and INTEGRAL (the International Gamma-ray Astrophysics Laboratory) reported the detection of the $\gamma$-ray counterpart, GRB 170817A, to the LIGO (Light Interferometer Gravitational-wave Observatory)/{\it Virgo} gravitational wave detected binary neutron star merger, GW 170817. GRB 170817A is likely to have an internal jet or other origin such as cocoon emission, shock-breakout, or a flare from a viscous disc. In this paper we assume that the $\gamma$-ray emission is caused by energy dissipation within a relativistic jet and we model the afterglow synchrotron emission from a reverse- and forward- shock in the outflow. We show the afterglow for a low-luminosity $\gamma$-ray burst (GRB) jet with a high Lorentz-factor ($\Gamma$); a low-$\Gamma$ and low-kinetic energy jet; a low-$\Gamma$, high kinetic energy jet; structured jets viewed at an inclination within the jet-half-opening angle; and an off-axis `typical’ GRB jet. The off-axis jet will produce a 10 GHz afterglow that peaks at $\sim 100$ days with a flux $\sim 10$ mJy. Only a high $\gamma$-ray efficiency low-luminosity jet, with either a high- or low- $\Gamma$, is consistent with a jet afterglow non-detection.
G. Lamb and S. Kobayashi
Tue, 17 Oct 17
107/163
Comments: 7 pages, 5 figures. Submitted to MNRAS
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