Observational Black Hole Spectroscopy: A time-domain multimode analysis of GW150914

Understand

The detection of the least damped quasi-normal mode from the remnant of the gravitational wave event GW150914 realised the long sought possibility to observationally study the properties of quasi-stationary black hole spacetimes through gravitational waves.

• Past literature has extensively explored this possibility and the emerging field has been named "black hole spectroscopy".
• In this study, we present results regarding the ringdown spectrum of GW150914, obtained by application of Bayesian inference to identify and characterise the ringdown modes.
• We employ a pure time-domain analysis method which infers from the data the time of transition between the non-linear and quasi-linear regime of the post-merger emission in concert with all other parameters characterising the source.