| Abstract: | Isolated spinning neutron stars, asymmetric with respect to their rotation
axis, are expected to be sources of continuous gravitational waves. The most
sensitive searches for these sources are based on accurate matched filtering
techniques, that assume the continuous wave to be phase-locked with the pulsar
beamed emission. While matched filtering maximizes the search sensitivity, a
significant signal-to-noise ratio loss will happen in case of a mismatch
between the assumed and the true signal phase evolution. Narrow-band algorithms
allow for a small mismatch in the frequency and spin-down values of the pulsar
while integrating coherently the entire data set. In this paper we describe a
narrow-band search using LIGO O2 data for the continuous wave emission of 33
pulsars. No evidence for a continuous wave signal has been found and
upper-limits on the gravitational wave amplitude, over the analyzed frequency
and spin-down volume, have been computed for each of the targets. In this
search we have surpassed the spin-down limit for some of the pulsars already
present in the O1 LIGO narrow-band search, such as J1400 extminus6325
J1813 extminus1246, J1833 extminus1034, J1952+3252, and for new targets such
as J0940 extminus5428 and J1747 extminus2809. For J1400 extminus6325,
J1833 extminus1034 and J1747 extminus2809 this is the first time the
spin-down limit is surpassed. |
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