Exploring the outflows and evolution of accreting neutron stars A multi-wavelength approach

Neutron stars and black holes (i.e. compact objects) are the evolutionary end states of massive stars, when these collapse and undergo a spectacular supernova explosion. These massive stars often form in binary systems, where mass transfer (accretion) can occur. When one of the stars in a binary system evolves into a compact object, its immense gravity causes accreted material to release vast amounts of energy, primarily emitted as X-rays. These systems are hence called “X-ray binaries”. X-ray binaries can also produce powerful outflows such as collimated jets, as well as winds launched from the accretion disc. This thesis is devoted to multi-wavelength observational studies of neutron stars in X-ray binaries, in particular to characterize their outflows and to understand certain aspects of their evolution. I combine X-ray and radio measurements to trace the coupling between the accretion inflow (via X-rays) and jet outflow (via radio), and investigate the role of additional X-ray emission from the neutron star surface in deriving the inflow-outflow behaviour. Furthermore, I use X-ray to near-infrared data to study accretion disc winds. I show that neutron star X-ray binaries can launch disc winds in much smaller systems than previously expected, and discuss the implications for the evolution of these systems. Finally, I present a study on the formation channel of a peculiar neutron star X-ray binary, and the impactful discovery of an unexpected velocity kick in its formation. I show that an uncommon supernova mechanism might impart velocity kicks, which was not previously realised.