UvA

Neutron stars are the most compact and magnetic type of stars known in the universe. If a neutron star resides in a binary orbit around another star, it can gravitationally capture (accrete) the outer gaseous layers or the stellar wind of this second star. Spiralling in towards the neutron star, this material heats up and emits brightly at X-ray energies, inspiring the name X-ray binaries of such systems. Only a fraction of the accreted material reaches the surface of the neutron star; a significant fraction of this matter and the liberated gravitational energy, can instead be launched from the system via either wide, slow disk winds or fast, collimated jets. This dissertation, entitled `the extremes of magnetic accretion’, observationally investigates the role of the neutron star’s magnetic field in regulating the accretion and ejection processes described above. In Part I, the focus is on weakly-magnetized neutron stars, aiming to measure the geometrical and ionization properties of the accretion flow, especially at low rates of accretion, and determine how the magnetic field affects these; for instance, by preventing gas from efficiently reaching the neutron star surface. In Part II, I shift attention to more strongly-magnetized neutron stars, where decades of searches never found the aforementioned jets. I present the first hints of such jets, followed by the first firm detection. Finally, in Part III, the weakly and strongly-magnetized neutron stars are combined into a new radio survey, expanding the first jet observations in the latter category.