Seminar: A nonlinear voice from GW250114 ringdown

With the recent completion of the fourth observation run of LIGO and Virgo, the total number of detected binary black hole systems increases to about three hundred, opening a window for precisely measuring black hole properties. The ringdown gravitational wave serves as a unique fingerprint of a black hole. Yet, extracting the rich spectrum of quasi-normal modes from ringdown presents significant data analysis challenges, partly due to the challenge to single out the ringdown phase in data. Various data analysis strategies have been developed to address this, including gating and inpainting to isolate the ringdown contribution. In this talk, I will first briefly review current observational evidence for ringdown from recent gravitational-wave events. 

I will then introduce my work: a novel data analysis framework that uses gating and inpainting to incorporate information from the pre-ringdown phase as an informed prior for ringdown analysis. Focusing on GW250114, the loudest event observed to date, I will discuss how recent theoretical progress on calculating quadratic mode coupling ratios have enabled us to identify evidence for quadratic modes in this event and to perform tests of general relativity.

Anyone interested is welcome to attend.