Search for continuous gravitational waves from neutron stars in globular cluster NGC 6544

LIGO Scientific Collaboration, Virgo Collaboration

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We describe a directed search for continuous gravitational waves in data from the sixth initial LIGO science run. The target was the nearby globular cluster NGC 6544 at a distance of ≈2.7  kpc. The search covered a broad band of frequencies along with first and second frequency derivatives for a fixed sky position. The search coherently integrated data from the two LIGO interferometers over a time span of 9.2 days using the matched-filtering F-statistic. We found no gravitational-wave signals and set 95% confidence upper limits as stringent as 6.0×10−25 on intrinsic strain and 8.5×10−6 on fiducial ellipticity. These values beat the indirect limits from energy conservation for stars with characteristic spin-down ages older than 300 years and are within the range of theoretical predictions for possible neutron-star ellipticities. An important feature of this search was use of a barycentric resampling algorithm which substantially reduced computational cost; this method is used extensively in searches of Advanced LIGO and Virgo detector data.
Original languageEnglish
Article number082005
Number of pages15
JournalPhysical Review D
Issue number8
Publication statusPublished - 19 Apr 2017


  • LIGO
  • gravitational waves
  • NGC 6544
  • gravitational wave detectors
  • neutron stars
  • pulsars


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