Ringdown spectroscopy of rotating black holes pierced by cosmic strings

Multiple gauge theories predict the presence of cosmic strings with different mass densities G?/c2. We derive an equation governing perturbations a rotating black hole pierced by straight, infinitely long string along its axis rotation and calculate quasinormal-mode frequencies such hole. then carry out parameter estimation on first detected gravitational-wave event, GW150914, hypothesizing that there is piercing through remnant, yielding constraint G?/c2 <3.8× 10?3 at 90% confidence interval comparable Bayes factor analysis for Kerr without string. In contrast to existing studies which focus mutual intersection strings, or network, our work focuses hole, characteristics can be identified in binary coalescence signals.