Validating continuous gravitational-wave candidates from a semicoherent search using Doppler modulation and an effective point spread function

Abstract

Following up large numbers of candidates in continuous gravitational wave searches presents a challenge, particularly in regard to computational power and the time required to manually scrutinize each of the candidates. It is important to design and test good follow-up procedures that are safe (i.e., minimize false dismissals) and computationally efficient across many search configurations. We investigate two existing follow-up procedures, or "vetoes", both of which exploit the Doppler modulation predicted in astrophysical signals. We take advantage of a well-established semicoherent search algorithm based on a hidden Markov model to study a wide variety of search configurations and to generalize the veto criteria by considering the overall veto performance in terms of efficiency and safety. The results can serve as a guideline for follow-up studies in future continuous gravitational wave searches using a hidden Markov model algorithm. The results also apply qualitatively to other semicoherent search algorithms.

Search for continuous gravitational waves from ten H.E.S.S. sources using a hidden Markov model

“…3) The Doppler modulation (DM) veto involves turning off the DM correction, which accounts for the Doppler shift due to the Earth's motion, and recomputing the log-likelihoods. Astrophysical signals usually become undetectable without this correction [94]. Therefore, candidates with comparable L in both the DM-on and DM-off searches are rejected.…”

“…Here, f 0 is the frequency of the path at t = 0 and δf 0 is the frequency spread due to the Doppler shift correction applied by the F−statistic, i.e. ±δf ≈ 10 −4 f 0 [94].…”

“…[82] and further studied in Refs. [53,94,96], this veto involves shifting the sky position away from the true source's location. The sky offset is related to the length of T coh such that as T coh increases, the offset decreases.…”