Constraining the Outflow Structure of the Binary Neutron Star Merger Event GW170817 with Markov-Chain Monte Carlo Analysis

Understand

The multi-wavelength non-thermal emission from the binary neutron star (BNS) merger GW170817 has raised a heated debate concerning the post-merger outflow structure.

• Both a relativistic structured jet viewed off-axis and a mildly relativistic quasi-spherical outflow can explain the observational data of GW170817 up to ~260 days.
• We utilize a physically motivated analytic two-parameter model called the "boosted fireball" for the outflow structure after it has expanded far from the merger site and has entered the self-similar coasting phase.
• This model consists of a family of outflows with a structure varying smoothly between a highly collimated ultra-relativistic jet and an isotropic fireball.