Abstract:
The recent all-sky low-frequency Einstein@Home search for continuous gravitational
waves in the data from the first observing run (O1) of Advanced
LIGO had > 6000 surviving candidates at the end of the last (most sensitive)
follow-up stage [1]. In order to identify and rule out candidates due to
detector artefacts, the DM-off veto was developed [2]. A coherent version of
the DM-off veto rejected more than 99.9% of the surviving candidates. In
this work, we investigate whether a semicoherent DM-off veto could exclude
noise candidates at earlier stages of the search. We characterise the veto on
this all-sky search and were able to exclude > 75% of the 36248 candidates
from the first stage of the all-sky search using the semicoherent version of
the veto. We find that we could save over 20000 hours of computational
time by using the veto at this stage. We further optimise the DM-off search
setups for the characterisation of the veto. It is observed that the DM-off
setup can be made coarser while maintaining its effectiveness for this all-sky
search. Lastly, we explore different DM-off search setups for characterising
and applying the semicoherent DM-off veto to candidates from a recent directed
search for continuous waves from three astrophysical sources — Vela
Jr., Cassiopeia A, and G347.3 — in LIGO O1 data.
