Deepest search yet for gravitational waves from binary neutron stars

Using LIGO/Virgo's third observing run, this search covered gravitational-wave frequencies from 50 to 1000 Hz and, for the first time with advanced detectors, orbital periods shorter than three days — territory never previously probed. No signal was found, but the null result is informative: neutron stars within 100 parsecs spinning faster than roughly 495 Hz must be nearly perfect spheres, with deformations no larger than 5.2 × 10⁻⁸ times their radius. The same data constrain internal fluid oscillation (r-mode) amplitudes to below 1.5 × 10⁻⁶ for the fastest rotators, squeezing the space where binary accretion could be building detectable asymmetries.