Searching for a Ringdown Overtone in GW150914

Understand

We reanalyze the GW150914 post-merger data searching for quasinormal modes beyond the fundamental, quadrupolar mode.

• There is currently an ongoing disagreement in the literature about whether, and to what extent, the data contains evidence for a quasinormal mode overtone.
• We use a frequency-domain approach to ringdown data analysis that was recently proposed by the authors.
• Our analysis has several advantages compared to other analyses performed mainly in the time domain; in particular, the source sky position and the ringdown start time are marginalized over (as opposed to simply being fixed) as part of a Bayesian ringdown analysis.