Revisiting the ringdown of GW150914

TL;DR

This paper defends the robustness of previous analyses of GW150914's ringdown, arguing that the evidence for black hole quasinormal modes is consistent and not due to noise anomalies, emphasizing the importance of understanding the physical interpretation.

Contribution

It demonstrates that claims of detecting overtones in GW150914 are not supported by data analysis choices and affirms the robustness of the original ringdown analysis.

Findings

Analysis is robust against data analysis choices

Strain after peak matches superposition of quasinormal modes

Claims of overtone detection are not supported by data

Abstract

We examine recent claims that evidence for an overtone in the ringdown of the GW150914 binary black hole merger was a result of noise anomalies. We cannot reproduce these claims, finding that our previous analysis of this event is robust to data analysis choices and consistent with the expectation that strain after the peak is well described as a superposition of quasinormal modes of the remnant black hole. We discuss the meaning and implications of establishing that any specific ringdown mode was detected, and argue that it is misguided to expect actual LIGO-Virgo data to inform the discussion of whether or why the merger looks linear.