PhD colloquium, location: Auditorium 0.02, MPIfR
Miquel Colom i Bernadich
Southern Galactic Pulsars with MeerKAT: Surveys, Timing, and Fun with Old and New Discoveries
Pulsars are highly magnetised, rapidly spinning neutron stars. Using the technique of pulsar timing, we can model their rotational slowdown with microsecond precision, tracking every single rotation. When found in compact binary systems, pulsar timing enables measurements of relativistic post-Keplerian corrections to the orbit, allowing tests of fundamental physics and precise stellar mass determinations. Despite the discovery of over 4,000 pulsars, many questions remain open, ranging from stellar mass distributions to the physics of dense matter, tests of theories of gravity and binary evolution, questions that can only be addressed through pulsar timing. In this PhD defence, I present new results on southern Galactic pulsars based on observations from two radio observatories with a privileged view of the southern Galactic plane: the Murriyang telescope in Parkes, Australia, and the SKA pathfinder MeerKAT in South Africa. Murriyang is a 64-metre single-dish telescope with wide instantaneous bandwidth coverage, while the 64 antennas of MeerKAT form the most sensitive radio interferometer in the Southern Hemisphere. Their combined use, and especially the high sensitivity of MeerKAT, has opened new scientific opportunities for studying southern Galactic pulsars. I will present discoveries from the MPIfR–MeerKAT Galactic Plane Survey, the first wide-field interferometric pulsar survey, which has led to over 80 new detections. Thanks to MeerKAT’s interferometric capabilities, the sky localisation of new pulsars is instantaneous, significantly accelerating the derivation of timing solutions. Among these discoveries is PSR J1208–5936, a double neutron star system that will merge within a Hubble time due to gravitational-wave emission. This system and the performance of the survey provide valuable constraints on the neutron star merger rate in the Milky Way. Newly discovered pulsar–white dwarf systems also offer promising insights into mass distributions and binary evolution pathways. I will also present precise stellar mass measurements of the massive pulsar–white dwarf binary PSR J1227–6208, based on joint timing with MeerKAT and Murriyang. Its companion is an oxygen–neon–magnesium white dwarf potentially near the Chandrasekhar limit. Using Bayesian inference to model dispersion-measure-induced timing noise, we constrain the companion’s mass to lie between 1.2 and 1.5 solar masses, confirming its massive nature. This is only the third such mass measurement for this type of system, made possible by the combined sensitivity and frequency coverage of both telescopes. These results demonstrate the complementary strengths of MeerKAT and Murriyang, and they highlight the scientific potential of future facilities such as MeerKAT+ and the SKA. In particular, MeerKAT’s surveys offer a valuable blueprint for the next generation of pulsar searches and timing experiments with the SKA.