The radio lighthouse from afar In search of distant pulsars

Modern radio-pulsar catalogues contain a large diversity of objects: young solitary pulsars and old ones in binary systems, periodic or sporadic emitters; bright and magnetized, or faint and even eclipsing. We study these by means of their radio pulses, a descriptive characteristic of magnetic field strength and emission mechanism. The most exotic pulsars can inform about the neutron-star equation of state; and about general relativity in the strong field regime. Finding new such objects requires very powerful telescopes coupled with advanced search techniques and computation. While there are nearly two thousand known Galactic radio pulsars, no such sources have been discovered in other, neighbouring galaxies. Pulsar discoveries in nearby galaxies could link Galactic and extragalactic pulsar populations, more reliably measure intergalactic medium and distances, and possibly explain fast radio bursts. This thesis focuses on targeted multi-frequency searches for radio pulsars and fast radio transients in afar regions of the Milky Way and nearby galaxies. We primarily employ two Dutch radio telescopes: LOFAR (at 150 MHz) and Westerbork (at 1400 MHz). Multi-frequency observations can tackle deleterious propagation effects (dispersion, scintillation, scattering) and remain sensitive to bright distant sources. The thesis addresses the following topics: real-time search pipeline auto-tuning optimization, telescope sensitivity limits for periodic and single pulses from extragalactic sources, systematic classification of the radio pulsars population, and their evolution.