Search For Gravitational-wave Trains With the Spacecraft Ulysses

We report on the search for periodic gravitational wave in the mHz band conducted with the spacecraft ULYSSES. Gravitational wave signals generally provide information about the distance of the source; ULYSSES' data have a ''ken'' for each kind of source one looks for; for binaries the galactic centre is accessible to our experiment. The Neyman Pearson method, with its two strategies of 'attempting detection' and getting a threshold for no detection, is carefully discussed. We did not find significant evidence for positive detection, but established, at the 90% confidence level, upper limits to the amplitude significantly better than previous work. The weaker condition SNR = 1 corresponds to signal amplitudes h which vary about from 3 10(-15) to 10(-15) from low to high frequencies. Similar results and thresholds have been obtained for chirped signals in the linear regime with a search in the plane spanned by the frequency f and its rate of increase beta. We have discussed these limits in relation to a possible, conventional binary system of black holes in the galactic centre as a source. We have found that the data are significant only in a small region of the plane (f, beta), where limits to the mass of the companion of a central black hole of 2 10(6) M. can be established. At SNR = 1 the limit is approximate to 6000 M..