The X-ray afterglow flat segment in short GRB 051221A: Energy injection from a millisecond magnetar?

Abstract

The flat segment, lasting ~104 s, in the X-ray afterglow of GRB 051221A represents the first clear case of strong energy injection in the external shock of a short gamma-ray burst (GRB) afterglow. In this work, we show that a millisecond pulsar with a dipole magnetic field ~1014 Gauss could well account for that energy injection. The good quality X-ray flat segment thus suggests that the central engine of this short burst may be a millisecond magnetar. © 2006 The Authors. Journal compilation © 2006 RAS.