Kinematic Evidence for Open Cluster Origins of Galactic Binary Neutron Stars

TL;DR

This study uses Gaia data and trajectory analysis to explore the origins of Galactic binary neutron stars, finding evidence that some may originate from open clusters rather than globular clusters.

Contribution

It provides the first kinematic analysis suggesting open clusters as a plausible formation channel for certain Galactic binary neutron stars.

Findings

Globular clusters are unlikely birthplaces for BNSs due to low encounter probabilities.

Open clusters show a significant probability of being BNS origins, exemplified by the case of PSR J0737-3039.

Theia 58 is identified as a plausible birthplace for PSR J0737-3039 based on encounter analysis.

Abstract

We investigate the potential birthplace of Galactic binary neutron star (BNS) systems through a kinematic analysis. Using high-precision astrometry from Gaia DR3, updated pulsar distances, and Monte Carlo sampling of astrometric errors, we integrate the past trajectories of 11 Galactic BNSs and 167 globular clusters plus 2967 open clusters, to search for past encounters. Our results suggest that BNS origin in globular clusters is unlikely, with low encounter probabilities (e.g., $\lesssim 0.5\%$ for NGC 5139) and requiring excessive ejection velocities. Conversely, our analysis indicates that open clusters are a non-negligible formation channel. Specifically, the double pulsar J0737$-$3039 shows a $13.9\%$ ($5.4\%$) probability of originating from the young cluster OC 0450 (Theia 58). Based on encounter proximity and time, we argue that Theia 58 is its more plausible birthplace. Our work provides kinematic evidence consistent with an open-cluster origin for a subset of field BNSs.