South Africa’s MeerKAT Radio Telescope discovers eight new millisecond pulsars

BY ELEONORA FERRONI (INAF)

A group of astronomers, led by the Italian National Institute of Astrophysics (INAF) and the Max Planck Institute for Radio Astronomy (MPIfR) in Germany, has discovered eight millisecond pulsars (all located within globular clusters) using South Africa’s MeerKAT radio telescope.

Detailed in a Monthly Notices of the Royal Astronomical Society paper, the impressive result comes from the synergic work of two of the MeerKAT Large Survey Proposals, TRAPUM (Transients and Pulsars with MeerKAT, led by the University of Manchester and the MPIfR) and MeerTime (led by the Swinburne University of Technology).These are the first pulsars discovered using MeerKAT, one of two SKA precursors in South Africa. Millisecond pulsars are among the most extreme objects in the Universe, spinning up to 700 times per second.

“We directed the MeerKAT antennas toward nine globular clusters, and we discovered new pulsars in six of them!” says the lead author, Dr Alessandro Ridolfi, a post-doctoral research fellow at INAF and MPIfR.

“One of the pulsars, named PSR J18233021G, is interesting because of its highly elliptical orbit, and massive companion. This system is likely the result of an exchange of partners: following a ‘close encounter’, the original partner was expelled and replaced by a new companion star”.

Tasha Gautam, doctoral researcher at the MPIfR and co-author of the paper, explains: “This particular pulsar could have a high mass, more than two times the mass of the Sun, or it could be the first confirmed system formed by a millisecond pulsar and a neutron star. If confirmed by current additional observations, PSR J1823-3021G will be a formidable laboratory for studying fundamental physics.“

“The MeerKAT radio telescope is a huge technological step forward for the research and the study of pulsars in the southern sky,” adds Dr Andrea Possenti from INAF.

The eight new pulsars are just the tip of the iceberg: the observations that led to their discovery used only about 40 of MeerKAT’s 64 dishes and focused only on the central regions of the globular clusters. This also highlights how powerful the SKAO’s mid-frequency telescope will be – with 197 dishes including the MeerKAT array – in searching for millisecond pulsars in the future.

The globular cluster NGC 6624 was captured by the NASA/ESA Hubble Space Telescope. The location of some of the pulsars hosted by the cluster has been highlighted in the inset: in red, the new pulsar G, found by MeerKAT. The cluster NGC 6624 is located in the constellation of Sagittarius at about 7880 light-years from the Sun.

CREDIT: A. Ridolfi et al./INAF/Hubble Space Telescope