A New Pulsar in Green Bank Telescope Searches of Ten Globular Clusters

TL;DR

This study used the Green Bank Telescope to search ten globular clusters, discovering a new binary millisecond pulsar in NGC 5986 and analyzing pulsar presence relative to cluster density and properties.

Contribution

It reports the discovery of a new pulsar and evaluates the relationship between cluster density, metallicity, and pulsar content, challenging some existing theoretical models.

Findings

Discovered a new binary millisecond pulsar in NGC 5986.

No pulsars found in clusters with densities below 10^3 L_sun pc^-3.

Exchange interaction rates overpredict pulsar numbers in studied clusters.

Abstract

We report the results of pulsar searches in ten globular clusters using the Robert C. Byrd Green Bank Telescope. One new binary millisecond pulsar has been discovered in NGC 5986 with P=2.6 ms, P_orb=1.3 d, and a minimum companion mass of 0.16 M_sun. The companion is most likely a Helium white dwarf. Eight of the globular clusters we searched have central densities <10^4 L_sun pc^-3, making this a good sample for studying the pulsar content of low density clusters. We find no evidence for pulsars in clusters with very low densities <10^3 L_sun pc^-3, consistent with theoretical predictions. Null results in many of clusters we searched with moderate densities indicate that these systems do not contain a bright MSP. Two clusters in particular, one with very low metallicity, stand in contrast to theoretical calculations by Ivanova et al. (2008). We also find that three body exchange interaction rates calculated by Phinney (1996) seem to over predict the pulsar content in the clusters we studied.