  We present a new veto procedure to distinguish between continuous
gravitational wave (CW) signals and the detector artifacts that can mimic their
behavior. The veto procedure exploits the fact that a long-lasting coherent
disturbance is less likely than a real signal to exhibit a Doppler modulation
of astrophysical origin. Therefore, in the presence of an outlier from a
search, we perform a multi-step search around the frequency of the outlier with
the Doppler modulation turned off (DM-off), and compare these results with the
results from the original (DM-on) search. If the results from the DM-off search
are more significant than those from the DM-on search, the outlier is most
likely due to an artifact rather than a signal. We tune the veto procedure so
that it has a very low false dismissal rate. With this veto, we are able to
identify as coherent disturbances >99.9% of the 6349 candidates from the recent
all-sky low-frequency Einstein@Home search on the data from the Advanced LIGO
O1 observing run [1]. We present the details of each identified disturbance in
the Appendix.
