Discovery of Millisecond Pulsars in the Globular Cluster Omega Centauri

The globular cluster Omega Centauri is the most massive and luminous cluster in the Galaxy. The $γ$-ray source FL8Y J1326.7$-$4729 is coincident with the core of the cluster, leading to speculation that hitherto unknown radio pulsars or annihilating dark matter may be present in the cluster core. Here we report on the discovery of five millisecond pulsars in Omega Centauri following observations with the Parkes radio telescope. Four of these pulsars are isolated with spin periods of 4.1, 4.2, 4.6 and 6.8 ms. The fifth has a spin period of 4.8 ms and is in an eclipsing binary system with an orbital period of 2.1 hours. Deep radio continuum images of the cluster centre with the Australian Telescope Compact Array reveal a small population of compact radio sources making it likely that other pulsars await discovery. We consider it highly likely that the millisecond pulsars are the source of the $γ$-ray emission. The long-term timing of these pulsars opens up opportunities to explore the dynamics and interstellar medium of the cluster.

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