Gamma-Rays from Globular Clusters

We attempt to expand the known population of millisecond pulsars (MSPs) and to add or modify their associations within the fourth Fermi catalog. MSPs are formed when a neutron star is spun up through the accretion of new material from a companion star. They are commonly found in globular clusters, because of the extremely high stellar density of these systems. We use 12 years of data collected by the Fermi Gamma-Ray Space Telescope to search for the cumulative signal from undetected MSPs in globular clusters. We employ a candidate list of 17 clusters that have ATNF pulsars within 0.3° of the cluster center and are not associated with a cluster in the Fermi catalog. Sources with low significance are then stacked together to extend the detection limit for sub-threshold populations.