Signature of gravitational radiation in afterglow of short Gamma-Ray Bursts?

Abstract

Short Gamma-Ray Bursts (GRBs), brief intense emission of $\gamma-$rays characterized by a duration shorter than 2 seconds that are plausibly powered by the coalescence of binary neutron stars, are believed to be strong gravitational wave radiation (GWR) sources. The test of such a speculation has been thought to be impossible until the performance of the detectors like advanced LIGO. Recently there has been growing evidence for the formation of highly-magnetized neutron star (i.e., magnetar) in the double neutron star mergers. In this work we re-examine the interpretation of the X-ray plateau followed by an abrupt decline detected in some short GRB afterglows within the supramassive magnetar model and find that the maximum gravitational mass of the non-rotating neutron stars is $\sim 2.3M_{\odot}$ and the observed duration of some X-ray plateaus are significantly shorter than that expected in the magnetic dipole radiation scenario, suggesting that the collapse of the supramassive magnetars has been considerably enhanced by the energy loss via GWR. Such a result demonstrates that the signature of GWR may have already existed in current electromagnetic data of short GRBs.