A novel method for the determination of the binary period distribution in globular clusters

Abstract

Globular cluster binaries are dynamically affected by interactions within their host cluster, leaving a signature on their orbital period distribution. As most disrupting interactions occur during the early evolution of the cluster (when the cluster is densest), the present-day intrinsic binary period distribution, in particular the hard-soft limit, can provide insight into the early cluster environment. However, constraining the period distribution is difficult due to observational biases. To overcome this, we developed a hierarchical method for fitting the period distribution. This method takes multi-epoch radial velocity data for stars in the cluster, fits the radial velocity curve for stars detected as radial velocity variable, and then uses these posterior samples to recover the intrinsic orbital period distribution. We validate the method using mock data and present the first results on the globular cluster NGC 3201. This will provide information about binaries, globular clusters, and topics such as gravitational waves.