Measurement of sub-dominant harmonic modes for gravitational wave emission from a population of binary black holes

Understand

Measurements of multiple harmonic modes in the gravitational wave signals from binary black hole events could provide an accurate test of general relativity, however they have never been observed before.

• The sub-dominant modes, other than the main (l = 2, m = 2) mode, are weak in amplitude and thus difficult to detect in a single event at the current sensitivity of the gravitational wave detectors.
• To recover sub-dominant modes, we propose an unmodeled method for summation of signals from a population of binary black holes.
• The method coherently stacks all the signal modes, effectively increasing their signal-to-noise ratio, so the amplified signal can be extracted from the noisy data.