Estimating Gamma-Ray Flux from Millisecond Pulsars Originating in Globular Clusters Near the Galactic Center

TL;DR

This paper models gamma-ray flux from millisecond pulsars in globular clusters near the Galactic Center using N-body simulations, suggesting they could significantly contribute to the observed gamma-ray excess.

Contribution

It introduces a detailed simulation-based approach to estimate gamma-ray flux from MSPs originating in globular clusters near the Galactic Center, incorporating stellar evolution and neutron star formation.

Findings

MSPs from modeled GCs contribute a small but notable gamma-ray flux.

The total MSP contribution could be much higher when considering all GCs.

MSPs may significantly contribute to the Galactic Center gamma-ray excess.

Abstract

In this study, we investigate the contribution of millisecond pulsars (MSPs) to the gamma-ray excess observed in the Galactic Center by analyzing data from high-resolution direct N-body simulations of six globular clusters (GCs) that experience close encounters with the nuclear star cluster. Using the {\phi}-GPU code, we tracked the orbits of individual neutron stars (NSs) formed during the simulations, assuming a fraction of these NSs evolve into MSPs. Our model includes state-of-the-art single stellar evolution code including prescription for neutron star formation. We estimated the gamma-ray flux from these MSPs, considering known values for their gamma-ray emission. Our results show that MSPs originating from the six modeled GCs contribute a small but non-negligible fraction of the observed gamma-ray flux. This finding suggests that the actual gamma-ray flux from MSPs could be much higher when considering the entire population of GCs, potentially significantly contributing to the gamma-ray excess. This study highlights the importance of considering MSPs in the Galactic Center, originating from nearby globular clusters, as a potential source of the observed gamma-ray excess. Future work will involve more sophisticated simulations incorporating binary stellar evolution and comparing the fraction of MSPs in observed GCs to refine our models and improve the accuracy of our estimates.