Yi-Zhong Fan, Xue-Feng Wu, Da-Ming Wei
Short Gamma-Ray Bursts (GRBs) are brief intense emission of $\gamma-$rays characterized by a duration shorter than 2 seconds and some, if not all of them, are likely powered by the coalescence of binary neutron stars. Sometimes the remnants may be supramassive highly-magnetized neutron stars (magnetars) with a typical rotational period $P_0 \sim 1$ ms and the rapid rotation prevents the gravitational collapse until a good fraction of the rotational energy has been lost. Plausible observational evidence for the short-living magnetar central engine reported in the literature is the X-ray plateaus followed by an abrupt decline identified in some short GRB afterglow. We however find that with a moderate/high radiation efficiency favored by the very dim optical afterglow emission, the observed duration of some X-ray plateaus are significantly shorter than that expected in the dipole radiation model (i.e., the magnetar collapsed considerably earlier than the prediction of the pure dipole radiation). We suggest that the gravitational radiation of the magnetar can enhance the collapse considerably and thus account for the "shortened" duration of the plateau. The corresponding gravitational radiation signal may be detectable for the proposed Einstein Telescope.
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http://arxiv.org/abs/1302.3328
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