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要旨:
We describe an F-statistic search for continuous gravitational waves from
galactic white-dwarf binaries in simulated LISA data. Our search method
employs a hierarchical template-grid-based exploration of the parameter space.
In the first stage, candidate sources are identified in searches using different
simulated laser signal combinations (known as TDI variables). Since each
source generates a primary maximum near its true ‘Doppler parameters’
(intrinsic frequency and sky position) as well as numerous secondary maxima
of the F-statistic in Doppler parameter space, a search for multiple sources
needs to distinguish between true signals and secondary maxima associated
with other ‘louder’ signals. Our method does this by applying a coincidence
test to reject candidates which are not found at nearby parameter space positions
in searches using each of the three TDI variables. For signals surviving the
coincidence test, we perform a fully coherent search over a refined parameter
grid to provide an accurate parameter estimation for the final candidates.
Suitably tuned, the pipeline is able to extract 1989 true signals with only 5
false alarms. The use of the rigid adiabatic approximation allows recovery of
signal parameters with errors comparable to statistical expectations, although
there is still some systematic excess with respect to statistical errors expected
from Gaussian noise. An experimental iterative pipeline with seven rounds
of signal subtraction and reanalysis of the residuals allows us to increase the
number of signals recovered to a total of 3419 with 29 false alarms.
