LIGO O2; gravitational waves from Scorpius X-1

We search for signals with ~constant frequency in the range 40-180Hz. Thanks to the efficiency of our search pipeline we can use a long coherence time and achieve unprecedented sensitivity, significantly improving on existing results.

This is the first search that has been able to probe gravitational wave amplitudes that could balance the accretion torque at the neutron star radius. Our search excludes emission at this level between 67.5 and 131.5Hz, for an inclination angle 44{deg}{+/-}6{deg} derived from radio observations, and assuming that the spin axis is perpendicular to the orbital plane. If the torque arm is ~26km-a conservative estimate of the Alfven radius-our results are more constraining than the indirect limit across the band.