Black holes and neutron stars are notorious for their enormous gravity that allows them to devour anything near them. However, these cosmic cannibals are messy eaters and fling gas and energy into space via so-called jets. These carry such enormous power that they play a key role in our universe. For instance, jets determine how galaxies develop, produce ultra-fast particles and enrich the cosmos with exotic elements. How jets are launched and energized remains, however, a mystery. In this project, an innovative technique is applied to astronomical observations of large telescopes to enforce a breakthrough in understanding jets.

Mass loss is one of the major sources of uncertainties in the evolution of massive stars. It can happen either via steady stellar winds, or via impulsive events on short timescales, or both. It can remove a large fraction of the stellar mass and influence the evolution and final fate of the star in ways that are currently poorly constrained. This is because mass loss is a dynamical phenomenon hard to implement in hydrostatic stellar evolution codes. These codes usually rely on parametric algorithms to evaluate the amount of mass to remove at each timestep. I aim to provide a systematic comparison of various algorithms for massive stars winds, and give better constraints on the uncertainties on stellar structures caused by the different algorithmic representation of the wind mass loss. I compute a grid of solar metallicity stellar models with MESA, varying the initial mass (in the range [15,40] solar masses), the mass loss algorithm and its efficiency, and compare the results at the end of the mass loss phase, at core oxygen depletion, and at the onset of core collapse. Different algorithmic representation of the same physical phenomenon (i.e. the wind mass loss) produce qualitatively and quantitatively different evolutionary tracks. The wind efficiency has the largest impact. However, the mass loss timing, the final appearance (i.e. effective temperature and luminosity), and to some extent the internal structure of the star depend on the algorithm adopted. The comparison of stellar evolution models using different mass loss algorithms is complicated by the systematic uncertainty connected to mass loss. This uncertainty is significant and needs to be considered when discussing the results of stellar evolution calculations.

We zijn van plan om de eerste driedimensionale algemeen relativistische magnetohydrodynamische (GRMHD) simulaties van accretie op gemagnetiseerde neutronensterren uit te voeren voor het geval dat de magnetische as niet goed is uitgelijnd met de stellaire spin. Dit zal ons in staat stellen om de fysieke mechanismen achter verschillende waargenomen fenomenen uit deze bronnen te onderzoeken, zoals de vorming van neutronensterren, de aanwezigheid van hoogfrequente quasi-periodieke oscillaties in de röntgenflux, en ook licht werpen op de eigenschappen van accretie-hotpots.

Fast radio bursts originate far outside our Milky Way and were only recently discovered. It is still a mystery how the bursts are produced, but it is clear that some sources repeat while others apparently do not. In this project, astronomers aim to understand the variety of fast radio bursts by using effects that are imparted on the signals by their local environment.

We have discovered an astonishing diversity of planets outside the Solar System. To better understand the nature, origins and fates of these new worlds, and our own, we will measure their atmospheric composition, climate, clouds, and weather systems occurring on these exoplanets. From the atmospheric composition measurements, we will trace planet formation and evolution processes that shape the population of exoplanet. This will be achieved via a portfolio of cutting-edge observations, combined with state-of-the-art models. The impact of our discoveries will go well beyond the scientific community since the quest of our origins is of interest to humankind.