First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

摘要

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources ofcontinuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars afully coherent search, based on matched filtering, which uses the position and rotational parametersobtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatchbetween the assumed and the true signal parameters. For this reason, narrow-band analysis methods havebeen developed, allowing a fully coherent search for gravitational waves from known pulsars over afraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initialoutliers, further studies show no significant evidence for the presence of a gravitational wave signal.Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 ofthe 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten forthe first time. For an additional 3 targets, the median upper limit across the search bands is below thespin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carriedout so far.