Comparison of unknown gravitational-wave signals in two detectors

We present a new measure that can be used to test the hypothesis that a similar signal has been recorded in the strains of two gravitational-wave detectors, without recurring to a priori templates or whitening of the strains.

For an evaluation of its properties we apply our measure to the LIGO data of the GW150914 event and detect the existence of a similar signal with 99.99% confidence level. We also use the new measure to study the strains in the gravitational-wave observatories for the events 151012_2, GW151012, GW170104 and GW190521; covering in this way a variety of different situations.

In addition we compare our measure with other standard measures and find that it is stronger for the studied data. Thus we are presenting a new powerful tool for the systematic study of unknown gravitational-wave signals in two or more observatories.