  We present a method for assigning a statistical significance to detection
candidates in targeted searches for continuous gravitational waves from known
pulsars, without assuming the detector noise is Gaussian and stationary. We
take advantage of the expected Doppler phase modulation of the signal induced
by Earth's orbital motion, as well as the amplitude modulation induced by
Earth's spin, to effectively blind the search to real astrophysical signals
from a given location in the sky. We use this "sky-shifting" to produce a large
number of noise-only data realizations to empirically estimate the background
of a search and assign detection significances, in a similar fashion to the use
of timeslides in searches for compact binaries. We demonstrate the potential of
this approach by means of simulated signals, as well as hardware injections
into real detector data. In a study of simulated signals in non-Gaussian noise,
we find that our method outperforms another common strategy for evaluating
detection significance. We thus demonstrate that this and similar techniques
have the potential to enable a first confident detection of continuous
gravitational waves.
