Fully coherent follow-up of continuous gravitational-wave candidates

The search for continuous gravitational waves from unknown isolated sources is computationally limited due to the enormous parameter space that needs to be covered and the weakness of the expected signals. Therefore, semicoherent search strategies have been developed and applied in distributed computing environments such as Einstein@Home, in order to narrow down the parameter space and identify interesting candidates. However, in order to optimally confirm or dismiss a candidate as a possible gravitational wave signal, a fully coherent follow-up using all the available data is required. We present a general method and implementation of a direct (two-stage) transition to a fully coherent follow-up on semicoherent candidates. This method is based on a gridless Mesh Adaptive Direct Search algorithm using the $\mathcal{F}$-statistic. We demonstrate the detection power and computing cost of this follow-up procedure using extensive Monte Carlo simulations on (simulated) semicoherent candidates from a directed, as well as from an all-sky search setup.