Projects

See a descriptions of some of our team's ongoing research projects below.

Searching for Alternative Polarization modes in the Gravitational Wave Background using MeerKAT

Atiqur Rahman, Jaikhomba Singha, Marisa Geyer, Ryan Shannon, Matt Miles

Pulsar Timing Arrays are now reaching sensitivity towards detecting angular spatial correlations described by the Hellings and Downs (HD) curve, as expected from binary mergers of a cosmic population of Super Massive Black Hole Binaries. The remarkable sensitivity of the MeerKAT telescope has enabled the detection of the HD curve in the MeerKAT Pulsar Timing Array (MPTA) dataset spanning $\sim$5 years. This HD signature results from the expected quadrupolar nature of the Gravitational Wave Background (GWB) specifically the $h_+$ and $h_{\times}$ polarisation modes. In this work, we investigate alternative GW polarisations, in particular the Scalar Transverse (ST) modes, along with the $h_+$ and $h_{\times}$ modes and consider the sensitivity of the MPTA dataset to ST modes. Such studies potentially provide excellent tests for modified gravity theories.

Searching for pulsars in the Large Magellanic Cloud as part of the TRAPUM programme on MeerKAT

Venu Prayag, Marisa Geyer, Lina-Levin Preston, Ben Stappers

The Large Magellanic Cloud (LMC), 50 kpc from Earth, is a unique nearby galaxy with lower metallicity, more star formation, and a higher number of supernova remnants and high-mass X-ray binaries than the Milky Way per unit mass. As part of the TRAPUM project, we are using MeerKAT’s excellent sensitivity to search for extragalactic radio pulsars in the LMC. With over three times the sensitivity of previous surveys, we can probe deeper, aiming to expand the known pulsar population in the LMC, which previously stood at only 25 pulsars.

Modelling Crab-like and Vela-like pulsars and their nebulae

Trevor Nyambe, Christo Venter, Ben Stappers

Pulsars, with their stable rotation and extreme environments, provide unique opportunities to explore fundamental physics. Despite progress in understanding pulsar magnetospheres and their wind nebulae (PWNe), key questions about their emission geometry, particle acceleration, and energy transfer remain a mystery. This project will investigate how pulsar properties, such as rotational period and emission beam characteristics, influence the dynamics of their nebulae. Using a combination of timing data and multi-wavelength modelling, the goal is to constrain the emission mechanisms and spatial energy distribution in Vela-like and Crab-like pulsars and their nebulae, contributing to a deeper understanding of high-energy astrophysics.

Ultralight dark matter searches with Pulsar Polarisation and Timing Arrays

Michael Sarkis, Yin-Zhe Ma

Polarised radio emissions from pulsars are expected to experience a birefringence effect as they traverse a region containing a field of ultralight dark matter (mass $~ 10^{-22}\, eV$). We search for signatures of this effect, which results in the rotation of the polarisation angle, through the correlation of many polarisation measurements from an array of pulsars.

Searching for an optical counterpart for Fast Radio Bursts

Kira Hanmer, Paul Groot, Ben Stappers

Fast radio bursts (FRBs) are bright, milli-second duration pulses of radio emission, of extragalactic origins. We still do not know what causes these bursts, although there are plenty of models that have been suggested. So far FRBs have only ever been observed at radio wavelengths, and this makes it challenging to rule out possible models from the long list. For this reason, observing FRBs at wavelengths other than the radio would be useful for trying to gain a better understanding of what causes these bursts. However, trying to find any kind of counterpart to FRBs is challenging, as most FRBs are only seen once, and they last for such a short time. This means that, although we can schedule observations in other wavelengths of known repeating FRBs, it is more difficult to search for counterparts for the non-repeating majority of FRBs. However, here in South Africa, we have MeerLICHT, which is a fully robotic wide-field optical telescope, located in Sutherland. MeerLICHT was commissioned specifically to observe simultaneously with MeerKAT, meaning that we have a unique opportunity to search for an optical counterpart to all kinds of FRBs - repeating or not. We are using MeerLICHT to search for optical counterparts to FRBs discovered by MeerTRAP.

Searching for persistent radio emission towards selected Fast Radio Burst positions

Thulo Letsele, Christo Venter, Tiaan Bezuidenhout

Fast Radio Bursts (FRBs) are brief radio emissions that occur at great distances in the cosmos, as indicated by their large dispersion measures, and last only a few milliseconds. Some FRBs manifest repeating bursts, and some have persistent radio emission associated with them. Detecting and characterising such persistent sources could provide insight into the evolution, energetics, and formation of FRBs. Progress in understanding FRB progenitors also depends on investigating the properties of their host galaxies, which show great demographic diversity. Thus, by investigating well-localised FRBs, we can detect associated radio continuum emissions, check for variability, and conduct follow-up multi-wavelength studies, including instruments such as Swift and H.E.S.S.

Timing pulsars in relativistic binaries with MeerKAT

Marisa Geyer, Jaikhomba Singha, Vivek Krishnan Venkatraman and members of the Meertime Relativistic Binary group

Pulsars in tight orbital period binary systems allow us to test theories of Gravity in extreme environments, or the strong field regime. The technique of pulsar timing allows us to obtain not just the standard Keplerian orbital parameters, but also the relativistic corrections required to describe the orbits precisely. These non-Keplerian include for example orbital precession, orbital decay through gravitational wave emission, gravitational redshift and Shapiro delay. Measuring such relativistic corrections precisely not only allows you to test e.g. the principles of General Relativity, but also leads to precise pulsar and component masses. Finding massive pulsars, and unveiling the pulsar mass distribution, in turn provides insights into the interiors of neutron stars and can be used to ultimately understand the neutron star equation of state.