Direct observational upper limit to gravitational radiation from millisecond pulsar PSR1937 + 214

Abstract

The newly discovered millisecond pulsar PSR1937 + 214 has such a high rotational rate, 642 Hz, that any significant quadrupole moment not aligned with the spin axis could lead to a large flux of gravitational radiation. Although recently reported^1–3 slowdown rates suggest an energy loss corresponding to a currently unobservable level of gravitational radiation, existing evidence may not completely rule out all possibilities for production of detectable gravitational waves. For example, continuing accretion might provide additional energy for gravitational radiation; and it may not be impossible that the pulsar might be closer to the Earth than indicated by the dispersion measure if there was large local dispersion. Overall, the parameters of this pulsar seem so exceptional that a direct search for gravitational radiation with existing equipment seemed worth making. We describe here such a search that has set an upper limit to gravitational wave amplitude at twice the pulsar rotation frequency, the observed output from a gravitational wave detector corresponding at this frequency to an amplitude of (0.8^+1.5_−0.8) × 10⁻²⁰.