Stellar-mass Black Hole Parameter Estimation Achieves Improved Accuracy with Center-of-Mass Acceleration

The subtle influence of external bodies on merging black holes presents a significant challenge for gravitational wave astronomy, and researchers are now quantifying the extent of this impact. Suvikranth Gera from IIT Guwahati and the Indian Association for the Cultivation of Science, along with Poulami Dutta Roy from the Chennai Mathematical Institute and the University of Florida, and their colleagues, investigate how neglecting the effect of a distant third body on a binary black hole system introduces errors when determining the properties of the merging pair. Their work demonstrates that ignoring the resulting ‘center-of-mass acceleration’ can lead to substantial inaccuracies in estimating key parameters like mass and size, potentially exceeding the inherent uncertainties of the measurement, particularly for systems observed by future, more sensitive detectors. This research highlights the critical need to account for these external influences when analysing gravitational wave signals from stellar-mass black holes with next-generation instruments like Cosmic Explorer and Einstein Telescope, ultimately improving the precision of black hole population studies.

A team investigated how neglecting the effect of a distant third body on a binary black hole system introduces errors when determining the properties of the merging pair, specifically mass and size.

Their work demonstrates that ignoring the resulting ‘center-of-mass acceleration’ can lead to substantial inaccuracies, potentially exceeding the inherent uncertainties of measurements, especially for systems observed by future, more sensitive detectors. This phenomenon is particularly relevant for binary black holes merging near a supermassive black hole, an event predicted to occur frequently. This study focuses on stellar-mass binary black holes and explores the potential for detection, demonstrating that the phase shifts caused by third-body interactions are potentially detectable with these advanced instruments.

Scientists accurately modeled how center-of-mass acceleration introduces a time-varying shift in the gravitational wave signal’s phase and developed a method to incorporate this shift into existing waveform models. The results indicate that neglecting this acceleration can lead to significant errors in determining key properties of the binary system, particularly for asymmetric binaries where the black holes have significantly different masses.

The team measured that an unaccounted acceleration can introduce biases exceeding statistical errors, and they established that future detectors like Cosmic Explorer and Einstein Telescope will be sensitive enough to not only detect these subtle effects but also to constrain the magnitude of the center-of-mass acceleration itself. This capability provides insights into the presence and characteristics of the distant third body, with the Einstein Telescope offering even greater precision due to its enhanced low-frequency sensitivity.

These findings have implications for understanding binary formation channels, distinguishing between isolated mergers and those assembled through dynamic interactions, and potentially tracing the growth of intermediate-mass black holes in dense environments. Refining waveform models to include these effects will be crucial for accurately interpreting observations from next-generation detectors and unlocking a more complete understanding of black hole mergers in complex gravitational environments.