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Title:ÌýBlack Holes and Neutron Stars Share Similar Natal Kick Distributions

Abstract:ÌýThe death of a massive star in a supernova explosion is believed to impart an impulsive velocity ‘kick’ to the remnant black hole or neutron star, which can profoundly influence the remnant’s subsequent dynamical evolution, its spin, the rate of gravitational wave merger events in binary systems, and other key parameters. Natal kicks also provide a potential probe for supernova mechanisms and energetics, though the magnitudes and underlying drivers of these natal kicks remain ill-understood. Based mainly on theoretical work, it has long been assumed that black holes receive smaller/negligible kicks compared to neutron stars, with typical magnitudes for each class differing by more than an order of magnitude. By contrast, here we show that the natal kick distributions of black holes and neutron stars are extremely similar and formally indistinguishable. Our method combines high-precision observations with binary population synthesis to infer the natal kick distribution, finding that black holes can receive large natal kicks and that kicks for all remnant types span similar ranges (from 0-750 km/s). Our results demonstrate that similar physics drives kicks and alleviates one of the key degeneracies in binary population synthesis modelling. If double compact objects suffer similar kicks, our results will improve merger rate predictions for gravitational wave detectors. We find that merger rates do not scale down monotonically with natal kick, likely due to enhanced mergers in highly perturbed and eccentric systems.

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