Ring-down gravitational waves and lensing observables: How far can a wormhole mimic those of a black hole?

TL;DR

This paper investigates how Ellis-Bronnikov wormholes can produce gravitational wave ring-down signals and lensing effects similar to black holes, challenging the uniqueness of black hole signatures and exploring their observational indistinguishability.

Contribution

It demonstrates that Ellis-Bronnikov wormholes can mimic black hole ring-down frequencies and lensing observables, showing potential observational degeneracy between these objects.

Findings

Wormhole quasinormal modes can be similar to black hole modes in the eikonal limit.

Lensing observables of wormholes can closely match those of black holes.

Wormhole parameters are constrained by current experimental accuracy.

Abstract

It has been argued that the recently detected ring-down gravity waveforms could be indicative only of the presence of light rings in a horizonless object, such as a surgical Schwarzschild wormhole, with the frequencies differing drastically from those of the horizon quasinormal mode frequencies $\omega _{\text{QNM}}$ at late times. While the possibility of such a horizonless alternative is novel by itself, we show by the example of Ellis-Bronnikov wormhole that the differences in $\omega _{\text{QNM}}$ in the eikonal limit (large $l$) need not be drastic. This result will be reached by exploiting the connection between $\omega _{\text{QNM}}$ and the Bozza strong field lensing parameters. We shall also show that the lensing observables of the Ellis-Bronnikov wormhole can also be very close to those of a black hole (say, SgrA$^{\ast }$ hosted by our galaxy) of the same mass. This situation indicates that the ring-down frequencies and lensing observables of the Ellis-Bronnikov wormhole can remarkably mimic those of a black hole. The constraint on wormhole parameter $\gamma $ imposed by experimental accuracy is briefly discussed. We also provide independent arguments supporting the stability of the Ellis-Bronnikov wormhole proven recently.