Pulsars and Millisecond Pulsars III: Tracing Compact Object Dynamics in Globular Clusters with NBODY6++GPU

TL;DR

This paper enhances direct N-body simulations of globular clusters by integrating pulsar spin evolution and magnetic field decay, enabling more realistic modeling of neutron star and pulsar dynamics over time.

Contribution

It introduces a framework and mathematical formulations to incorporate pulsar physics into NBODY6++GPU simulations, addressing previous limitations.

Findings

Neutron star formation and evolution tracked over 200 Myr without pulsar physics

Comparison of different pulsar evolution scenarios outlined

Implementation details provided for integrating pulsar physics into N-body code

Abstract

Neutron stars in globular clusters follow complex evolutionary pathways shaped by binary interactions, mass transfer, and dynamical exchanges. Direct N-body simulations such as NBODY6++GPU successfully model stellar dynamics and compact object formation, but they usually do not track pulsar spin evolution or magnetic field decay explicitly. Building on Papers I and II of this series, we identify this gap and present a case study from an existing simulation with N = 105000 particles, showing how a neutron star forms and evolves for 200 Myr without any pulsar-physics tracking. We compare this situation with recent implementations and outline a seven-scenario framework that includes magnetic dipole spin-down, exponential magnetic field decay, environmental torques, accretion-driven spin-up, gravitational-wave emission, and merger-driven evolution. As an example, the neutron star we label Pulsar973 forms at t = 800 Myr with a post-supernova mass of 5.35 solar masses and evolves to 2.52 solar masses by t = 1000 Myr, but still lacks period P, period derivative Pdot, magnetic field B, and scenario classification. We provide mathematical formulations and specific integration points within NBODY6++GPU (Hermite scheme, Ahmad-Cohen neighbors, KS regularization, and BSE stellar evolution) to enable scenario-based pulsar evolution within direct N-body simulations.