Pulsars and Millisecond Pulsars IV: From Subroutine Validation to Population Synthesis in NBODY6++GPU

Vollständiger Abstract

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Direct N-body codes such as NBODY6++GPU can solve the dynamical evolution of globular clusters with great accuracy, yet historically uses simple models: spin period, spin-down rate, and magnetic field strength are never updated once a neutron star forms. Earlier works in this series identified this gap, proposed a seven-scenario framework (S1–S7) covering the full range of pulsar evolutionary channels, and demonstrated the absence of pulsar tracking in an existing cluster simulation. Here we bring together three subsequent stages that solve this gap. A pulsar evolution subroutine was first tested in isolation across all seven scenarios, with two independently written codes agreeing to better than 0.1% over more than two thousand compared values, and reproducing accretion-driven spin-up for the first time within this framework. The validated framework was then embedded directly into NBODY6++GPU, and test integrations spanning timescales from under a Megayear up to a Gigayear show that the resulting period-period derivative distribution already resembles the pattern seen in real globular cluster pulsar populations. Finally, an early production test followed ten neutron stars self-consistently through the integrated code over roughly 28 Myr, uncovering that most of them pass through at least one episode of backward evolution, a behaviour that only becomes visible when spin parameters are sampled at every simulation step rather than inferred afterwards. Taken together, these results show that pulsar physics can now evolve as an integral part of cluster dynamics rather than a separate bookkeeping exercise, setting the stage for a full production run at N = 250,000.