cWB is a data analysis pipeline designed for the detection and reconstruction of unmodeled gravitational-wave (GW) transients, also known as “bursts.” Unlike matched-filter searches that target known waveform templates (e.g., from compact binary coalescences), cWB searches for coherent excess power across the global gravitational-wave detector network without assuming a specific signal model. It is one of the primary pipelines used by the LIGO, Virgo, and KAGRA collaborations for the detection of short-duration GW signals.
Key Features
Model-Independent Detection
cWB identifies GW signals by looking for statistically significant, coherent energy in the time-frequency domain across multiple detectors. It does not rely on predefined waveform templates, making it ideal for detecting unexpected or poorly modeled signals, such as those from core-collapse supernovae, cosmic string cusps, or eccentric mergers.
Coherent Multi-Detector Analysis
The pipeline combines data from multiple detectors to reconstruct the most probable GW signal and source sky location. It uses likelihood-based methods to separate genuine astrophysical signals from noise artifacts.
Time-Frequency Reconstruction
Uses wavelet transforms to map detector data into the time-frequency domain, where it identifies and clusters regions of excess energy. This allows cWB to reconstruct signal morphology, duration, and bandwidth.
Sky Localization and Source Reconstruction
Provides sky localization maps and estimates of source parameters such as arrival time, signal duration, and polarization. These outputs are useful for triggering electromagnetic or neutrino follow-up observations.
Low-Latency and Offline Modes
Operates in both real-time (low-latency) for issuing rapid alerts to the astronomical community and in offline mode for archival searches with refined calibration and data quality.
Signal Consistency and Vetoes
Implements consistency checks and noise-rejection techniques, including null-stream reconstruction and data-quality vetoes, to reduce false positives and improve detection confidence.
Sensitivity to a Broad Range of Sources
Capable of detecting short-duration bursts (milliseconds to seconds), including compact binary mergers, eccentric inspirals, magnetar flares, and high-frequency GW emission.
Use Case
cWB is widely used in gravitational-wave science for:
- Detecting and reconstructing short-duration signals that do not match existing waveform models.
- Searching for gravitational-wave counterparts to poorly understood astrophysical phenomena.
- Issuing rapid alerts for multi-messenger follow-up.
- Performing robustness checks alongside templated searches for compact binary coalescences.
In summary, cWB is a powerful, model-agnostic gravitational-wave search pipeline that plays a critical role in both discovery science and multi-messenger astrophysics. Its ability to identify unexpected or poorly modeled transients makes it an essential component of the global effort to explore the dynamic universe through gravitational waves.