SGR 1806-20 and the gravitational wave detectors EXPLORER and NAUTILUS

摘要

The activity of the soft gamma ray repeater SGR 1806-20 is studied incorrelation with the EXPLORER and NAUTILUS data, during the year 2004, forgravitational wave (GW) short signal search. Corresponding to the mostsignificant triggers, the bright outburst on October 5th and the giant flare(GF) on December 27th, the associated GW signature is searched. Two methods areemployed for processing the data. With the average-modulus algorithm, thepresence of short pulses with energy Egw \geq 1.8 x 10^49 erg is excluded with90% probability, under the hypothesis of isotropic emission. This value iscomparable to the upper limits obtained by LIGO regarding similar sources.Using the cross-correlation method, we find a discrepancy from thenull-hypothesis of the order of 1%. This statistical excess is not sufficientto claim a systematic association between the gravitational and theelectromagnetic radiations, because the estimated GW upper limits are yetseveral orders of magnitude far away from the theoretically predicted levels,at least three for the most powerful SGR flare.