Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data

This paper presents results of an all-sky search for periodic gravitational waves in the frequencyrange [50, 1 190] Hz and with frequency derivative range of ∼ [−20, 1.1] × 10−10 Hz s−1 for thefifth LIGO science run (S5). The search uses a non-coherent Hough-transform method to combinethe information from coherent searches on timescales of about one day. Because these searchesare very computationally intensive, they have been carried out with the Einstein@Home volunteerdistributed computing project. Post-processing identifies eight candidate signals; deeper follow-upstudies rule them out. Hence, since no gravitational wave signals have been found, we report upperlimits on the intrinsic gravitational wave strain amplitude h0 . For example, in the 0.5 Hz-wide bandat 152.5 Hz, we can exclude the presence of signals with h0 greater than 7.6 × 10−25 at a 90%confidence level. This search is about a factor 3 more sensitive than the previous Einstein@Homesearch of early S5 LIGO data.