A Noise Filter for Gravitational Waves express
Gravitational-wave detectors are like sensitive microphones, listening for the whispers of distant cataclysms. But every now and then, a sharp crack bursts in — a brief noise spike known as a glitch. Such a crack can resemble a real signal from a black hole merger, and astronomers risk mistaking noise for a discovery.
A new tool, bilby_glitch, works like a sound engineer who hears both the music and the clicks in a recording at the same time. It doesn't try to guess where the signal is and where the glitch is: it builds a model of both right away. It's based on the popular program bilby, to which three noise models were added: slow scattering (like an echo off a wall), a sine-Gaussian burst, and a chirplet — a short signal with a changing frequency, similar to the whistle of a falling rocket.
The method was tested on two real events. For GW191109, the result matched previous analyses — a calm case. But GW200129 proved to be finicky. When the glitch was modeled with wavelets (short wave bursts) and the signal with the IMRPhenomXPHM approximation, the black hole's spin looked confident. However, when the more accurate NRSur7dq4 approximation was used for the signal, the evidence for spin nearly vanished. The takeaway: our ideas about how a black hole spins can depend on how we clean the sound.
So astronomers get not just a tool, but a reminder: in the silence of space, even a tiny glitch can change the story.
Original abstract
as written by the authors arXiv:2607.09111
Non-Gaussian noise transients ("glitches") in gravitational-wave observatories degrade our ability to accurately perform astrophysical inference. We present the analysis pipeline bilby_glitch, which allows for simultaneous Bayesian inference of gravitational-wave signals and glitches. Our framework is modular and built on top of the popular bilby framework, facilitating future extensions with additional glitch and signal models. We integrate transdimensional bilby into our framework and discuss three glitch models: a physically-motivated slow scattering model, and flexible sine-Gaussian and chirplet models. Using a combination of simulated and real data, we demonstrate that bilby_glitch produces reliable results. We then reanalyse two gravitational-wave events - GW191109 and GW200129 - which show signs of interesting black-hole spins, but which may also be affected by data-quality issues. Our results for GW191109 are consistent with previous analysis. For GW200129, we recover results consistent with Payne et al., where the evidence of spin-precession is much weaker when using the waveform approximant NRSur7dq4 in combination with wavelet-based glitch modeling. Furthermore, we show the astrophysical conclusion of this event is dependent on the interplay between the waveform approximant and glitch model, since in contrast to NRSur7dq4 we find that inference with the waveform approximant IMRPhenomXPHM shows strong evidence of spin-precession when used in combination with wavelet-based glitch modeling.
Glitches in LIGO detectors are sometimes called "whales" or "ravens"—each type has its own onomatopoeic name based on the signal's shape.