Timing of Millisecond Pulsars in NGC 6752 – III. on the Presence of Non-Luminous Matter in the Cluster's Core

Millisecond pulsars are subject to accelerations in globular clusters that manifest themselves in both the first and second spin period time derivatives, and can be used to explore the mass distribution of the potentials they inhabit. Here we report on over 20 years of pulsar timing observations of five millisecond radio pulsars in the core of the core-collapse globular cluster NGC 6752 with the Parkes (Murriyang) and MeerKAT radio telescopes, that have allowed us to measure the proper motions, positions and first and second time derivatives of the pulsars. The pulsar timing parameters indicate that all the pulsars in the core experience accelerations and jerks that can be explained only if an amount of non-luminous mass of at least 2.56×10^3M_⊙ is resent in the core of NGC 6752. On the other hand, our studies highly disfavour the presence of an intermediate mass black hole at the center of the cluster, with a mass equal to or greater than ∼3000M_⊙.