LIGO Document P2000407-v17
- We present a search for continuous gravitational-wave signals from the young, energetic X-ray pulsar PSR J0537-6910 using data from the second and third observing runs of LIGO and Virgo. The search is enabled by a contemporaneous timing ephemeris obtained in X-rays using NICER data that has also been extended through 2020 October and includes 3 new glitches. PSR J0537-6910 has the largest spin-down luminosity of any pulsar and is highly active with regards to glitches. Analyses of its long-term and inter-glitch braking indices provided intriguing evidence that its spin-down energy budget may include gravitational-wave emission from a time-varying mass quadrupole moment. Its 62 Hz rotation frequency also puts its possible gravitational-wave emission in the most sensitive band of LIGO/Virgo detectors. Motivated by these considerations, we search for gravitational-wave emission at both once and twice the rotation frequency. However, we do not find a signal and report our upper limits. Assuming a rigidly rotating triaxial star, our constraints surpass for the first time the gravitational-wave spin-down limit by more than a factor of two and limit gravitational waves from the l=m=2 mode to account for less than 14% of the spin-down energy budget. The fiducial equatorial ellipticity is limited to less than about 3x10^-5, which is the third best constraint for any young pulsar.
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