Low-frequency radio transients Systematic search methods and characterization

This thesis explores astrophysical sources that exhibit transient radio emissions, focusing on how they can be detected and characterized. Transient events show emission that varies over timescales from milliseconds to years. They offer unique insights into the dynamic processes of the Universe, particularly in extreme conditions that cannot be replicated on Earth. These dynamic processes provide crucial information about the birth, evolution, and death of stars, and about complex processes like stellar mergers and material accretion between stars.
Low-frequency radio emissions, often generated by non-thermal processes, can reveal high-energy astrophysical activities, because it involves relativistic particles. The study of radio transients is thus important to develop our understanding of the emission processes related to highly energetic charged particles, often found in extremely dense or highly magnetic environments.
The research in this thesis is based on an image domain approach to find radio transients: monitoring fast transients via a novel approach using high time-resolution snapshots, and monitoring slow transients using long-integration high-quality survey images. Next to identifying radio transients, three chapters in this thesis focus on the characterization of specific sources like the recurrent nova RS Ophiuchi, a short gamma-ray burst associated with a neutron star merger, and a M-dwarf and white dwarf binary system that emits radio flares. These studies contribute to understanding the diverse and complex nature of transient astrophysical phenomena.