Brightening X-ray/Optical/Radio Emission of GW170817/SGRB 170817A: Results of an Electron-Positron Wind from the Central Engine?

Understand

Recent follow-up observations of the binary neutron star (NS) merging event GW170817/SGRB 170817A reveal that its X-ray/optical/radio emissions are brightening continuously up to $\sim 100$ days post-merger.

• This late-time brightening is unexpected from the kilonova model or the off-axis top-hat jet model for gamma-ray burst afterglows.
• In this paper, by assuming that the merger remnant is a long-lived NS, we propose that the interaction between an electron-positron-pair ($e^+e^-$) wind from the central NS and the jet could produce a long-lived reverse shock, from which a new emission component would rise and can interpret current observations well.
• The magnetic-field-induced ellipticity of the NS is taken to be $4 \times 10^{-5}$ in our modeling, so that the braking of the NS is mainly through the gravitational wave (GW) radiation rather than the magnetic dipole radiation, and the emission luminosity at early times would not exceed the observational limits.