Neutron star natal kicks and the long-term survival of star clusters

TL;DR

This study uses N-body simulations to explore how neutron star natal kicks influence the long-term survival and dissolution modes of star clusters, revealing that even a small neutron star mass fraction can significantly affect cluster lifetime.

Contribution

It demonstrates that neutron star natal velocity kicks can alter star cluster lifetimes by up to four times, highlighting their impact on cluster dissolution processes.

Findings

Neutron star kicks can significantly extend or shorten cluster lifetimes.

Cluster dissolution modes are influenced by neutron star kinematic properties.

Mass loss profiles depend on the interplay between stellar evolution and dynamical relaxation.

Abstract

We investigate the dynamical evolution of a star cluster in an external tidal field by using N-body simulations, with focus on the effects of the presence or absence of neutron star natal velocity kicks.We show that, even if neutron stars typically represent less than 2% of the total bound mass of a star cluster, their primordial kinematic properties may affect the lifetime of the system by up to almost a factor of four. We interpret this result in the light of two known modes of star cluster dissolution, dominated by either early stellar evolution mass loss or two-body relaxation. The competition between these effects shapes the mass loss profile of star clusters, which may either dissolve abruptly ("jumping"), in the pre-core-collapse phase, or gradually ("skiing"), after having reached core collapse.