Mimicking mergers: mistaking black hole captures as mergers

As the number of gravitational wave observations has increased in recent years, the variety of sources has broadened. Here, we investigate whether it is possible for the current generation of detectors to distinguish between very short-lived gravitational wave signals from mergers between high-mass black holes and the signal produced by a close encounter between two black holes, which results in gravitational capture and ultimately a merger. We compare the posterior probability distributions produced by analysing simulated signals from both types of progenitor events, both under ideal and realistic scenarios. We show that while under ideal conditions it is possible to distinguish both progenitors, under realistic conditions they are indistinguishable. This has important implications for the interpretation of such short signals, and we therefore advocate that these signals be the focus of additional investigation even when satisfactory results have been achieved from standard analyses.