
A precomputed waveform model used to match against detector data to identify a gravitational-wave signal.A template is a precomputed model of a gravitational-wave signal, essentially a theoretical prediction of the exact waveform that a specific astrophysical event (like the merger of two black holes) would produce. In gravitational-wave astronomy, detectors like LIGO and Virgo record tiny vibrations of spacetime, but these signals are buried in noise. To find them, researchers compare the detector data against a bank of thousands of templates, each representing a different possible source (different masses, spins, etc.). When a template matches the data closely enough, it signals a detection and also reveals the properties of the source.
The concept of matched filtering with templates was borrowed from radar and sonar technology and adapted for gravitational waves in the 1970s by researchers like Kip Thorne and Bernard Schutz. The first direct detection in 2015 relied on extensive template banks built by the LIGO and Virgo collaborations.
The process is like pattern matching: the detector output is a continuous stream of noisy data. A template is a mathematical function that predicts the expected strain (the stretching and squeezing of space) over time for a specific event. The data and each template are cross-correlated — essentially, the template is slid along the data and the overlap is calculated. If the overlap exceeds a statistical threshold, it indicates that the signal is present. The best-matching template then provides the parameters of the event, such as the masses and spins of the merging objects.
Templates are the standard method for detecting gravitational waves from compact binary mergers, enabling the discovery of dozens of events and the study of black hole populations.
The template bank for LIGO contains over 250,000 individual waveforms, each computed from general relativity, to cover all possible binary configurations.


















