Fully coherent follow-up of continuous gravitational-wave candidates: An application to Einstein@Home results

We characterize and present the details of the follow-up method used on the most significant outliers of the Hough Einstein@Home all-sky search for continuous gravitational waves [J. Aasi et al Phys. Rev. D 87, 042001 (2013)]. This follow-up method is based on the two-stage approach introduced by [M. Shaltev and R. Prix, Phys. Rev. D 87, 084057 (2013)], consisting of a semicoherent refinement followed by a fully coherent zoom. We quantify the efficiency of the follow-up pipeline using simulated signals in Gaussian noise. This pipeline does not search beyond first-order frequency spin-down, and therefore we also evaluate its robustness against second-order spin-down. We present the details of the Hough Einstein@Home follow-up [J. Aasi et al Phys. Rev. D 87, 042001 (2013)] on three hardware-injected signals and on the eight most significant search outliers of unknown origin.