Gamma-ray burst afterglows and evolution of postburst fireballs with energy injection from strongly magnetic millisecond pulsars

TL;DR

This paper models the evolution of gamma-ray burst afterglows influenced by energy injection from strongly magnetic millisecond pulsars, explaining observed lightcurve behaviors.

Contribution

It introduces a model for postburst fireball evolution with magnetic dipole energy injection, explaining complex afterglow lightcurves.

Findings

Optical afterglow initially decreases then flattens and declines again.

Model explains the lightcurve of GRB970228.

Energy injection from pulsars affects afterglow evolution.

Abstract

Millisecond pulsars with strong magnetic fields may be formed through several processes, e.g. accretion-induced collapse of magnetized white dwarfs, merger of two neutron stars. During the birth of such a pulsar, an initial fireball available for a gamma-ray burst (GRB) may occur. We here study evolution of a postburst relativistic fireball with energy injection from the pulsar through magnetic dipole radiation, and find that the magnitude of the optical afterglow from this fireball first decreases with time, subsequently flattens, and finally declines again. This may provide a natural explanation for the behavior of the lightcurve of the afterglow of GRB970228 if this burst resulted from the birth of a strongly magnetic millisecond pulsar.