Tracking Black Hole Kicks from Gravitational-Wave Observations

Area of Science:

• Astrophysics
• Gravitational Wave Astronomy
• General Relativity

Background:

• Coalescing binary black holes emit gravitational radiation.
• This anisotropic emission results in a net momentum loss, imparting a recoil velocity (gravitational kick) to the final black hole.
• The characteristics of this kick are linked to the symmetries and modes of the emitted gravitational waves.

Purpose of the Study:

• To utilize higher-order gravitational wave modes to infer the radial component of the gravitational kick.
• To determine the feasibility of measuring this radial kick with current gravitational wave detectors.

Main Methods:

• Parameter inference was performed on simulated gravitational wave signals.
• Numerical relativity waveforms for nonspinning and aligned-spin binary black holes were used as templates.
• Analysis focused on identifying the radial kick component from gravitational wave emission modes.

Main Results:

• For binary black holes with mass ratio q≥2 and total mass ~100 solar masses, a radial kick of 120 km/s can be excluded as zero with 90% credible intervals.
• This detection is possible at a signal-to-noise ratio of 15 using a single Advanced LIGO detector at early sensitivity.
• The study demonstrates the potential to measure the radial kick component.

Conclusions:

• Measuring a nonzero radial kick would provide the first direct observational evidence of linear momentum transport by gravitational waves.
• Higher-order gravitational wave modes contain crucial information for inferring black hole recoil velocities.
• This research opens avenues for testing fundamental physics with gravitational wave observations.