Risbud et al. present describe the discovery of PSR J0024−7204ai, a 13.026 millisecond binary pulsar in the globular cluster 47 Tucanae. 47 Tuc ai was first detected in a MeerKAT observation in 2019 as a candidate pulsar with a barycentric line of sight acceleration of 4.02 m s−2 The large acceleration clearly pointed towards a binary nature, and opened the possibility that the pulsar had been missed in previous searches. Murriyang, the Parkes radio telescope, regularly observed 47 Tuc from 1997 to 2013 with the Multibeam receiver and from 2019 onwards has observbed the globular cluster with the Ultra-Wide bandwidth Low (UWL) receiver and so the team used this archival data in their study. After building a basic ephemeris all available data were searched to refine the orbital parameters. This led to the detection of the pulsar in a few additional MeerKAT observations, where the pulsar was not detected blindly, as well as in three different Parkes observations, dating back to the year 2000. The three Parkes detections turned out to be very important for the precise measurement of the periastron advance.
The figure above shows the Period-Acceleration diagram for 47 Tuc ai. The data points are the barycentric spin periods and line-of-sight accelerations as measured on seven different epochs where the pulsar was blindly detected. The best-fit parametric curve (solid black line), implying a mild orbital eccentricity (e ≈ 0.18). Apart from being the slowest pulsar in 47 Tucanae, its orbit is by far the most eccentric and its companion is the most massive among all known binary pulsars in this globular cluster. Further follow-up observations of this system will be essential for a more detailed characterisation of this system and its evolution.