Binary Natal Kicks in the Galactic Center: X-ray Binaries, Hypervelocity Stars, and Gravitational Waves

TL;DR

This study investigates how two successive natal kicks affect stellar binaries near the Galactic Center, leading to diverse dynamical outcomes, hypervelocity objects, and gravitational wave event rates, with implications for understanding black hole kicks.

Contribution

It introduces a detailed analysis of the impact of multiple natal kicks on binary dynamics and their observational signatures in the Galactic Center environment.

Findings

Hypervelocity stars and binaries are common outcomes of natal kicks.

X-ray binaries can diagnose black hole natal kick distributions.

Estimated gravitational wave event rates from kicks include mergers and EMRIs.

Abstract

Theoretical and observational studies suggest that stellar binaries exist in large numbers in galactic nuclei like our own Galactic Center. Neutron stars (NSs), and debatedly, black holes (BHs) and white dwarfs (WDs), receive natal kicks at birth. In this work we study the effect of two successive natal kicks on a population of stellar binaries orbiting the massive black hole (MBH) in our Galactic Center. These natal kicks can significantly alter the binary orbit in a variety of ways, and also the orbit of the binary around the MBH. We found a variety of dynamical outcomes resulting from these kicks, including a steeper cusp of single NSs relative to the initial binary distribution. Furthermore, hypervelocity star and binary candidates, including hypervelocity X-ray binaries, are a common outcome of natal kicks. In addition, we show that the population of X-ray binaries in the Galactic Center can be used as a diagnostic for the BH natal kick distribution. Finally, we estimate the rate of gravitational wave (GW) events triggered by natal kicks, including binary mergers and EMRIs.