Speaker
Description
GW190521 in a class of its own is a different signal, being the most massive BBH event observed to date. The exceptionally dominant ringdown of this event and its large mass makes it a plausible candidate to search for GW echoes. In this letter we perform an unprecedented search in two different platforms, satisfying a physical template (matched filtering and MCMC with PyCBC) and model agnostic search (Coherent WaveBurst-cWB). We expect the existence of post-merger horizon mode frequencies $m\times\Omega_{H}$ (with m=2 for quadrupolar gravitational radiation) as a consequence of BBH merger non-linear dynamics and Planck scale Boltzmann reflection near the would be event horizon. In this search, with a careful bayesian inference approach using dynamic nested sampling MCMC algorithm, we found $ln\mathcal{B}^{\rm{IMRE}}_{\rm{IMR}}= +2.0$ evidence for such frequencies and their echoes in GW190521. On the other hand, the results obtained via cWB supports that main event and the echo are preferably co-localized, $\mathcal{B}^{\rm{co-loc}}_{\rm{non co-loc}}\approx 7.1$. Additionally, accounting for all the "look-elsewhere" effects, we find tentative evidence for GW echoes at false detection probability of $2.5\times 10^{-3}$, using cWB pipeline.
