The winner of this year's Committee for Astroparticle Physics in the Netherlands (CAN) Thesis Prize is Wouter van Zeist, for his thesis "LISA gravitational wave sources from binary stellar evolution models." The research was carried out at Radboud University under the supervision of Prof. Gijs Nelemans, Prof. Jan Eldridge, and Prof. Simon Portegies Zwart. This competitive prize evaluates theses across a broad range of topics in astroparticle physics. In making its decision, the committee considered the following criteria: contribution to academic knowledge, originality of approach, soundness of methodology, and impact of the research.
This thesis focuses on predicting the true size of the Galactic population of compact binary sources observable by LISA, the Laser Interferometer Space Antenna. LISA is the next major gravitational-wave observatory which will be sensitive to a unique population of sources: compact binaries, especially white dwarf pairs, orbiting each other every few minutes, within our own galaxy. Before LISA launches, it's necessary to establish roughly how many of these sources exist and how they're distributed, since this determines how the data analysis pipelines are designed and how the resulting detections should be interpreted.
The theoretical predictions for this population have so far been uncertain. Different simulation codes, which model how binary stars evolve and interact over billions of years, produce different answers, in some cases by large factors. Wouter's thesis addresses this problem directly, using several complementary approaches. He worked with population synthesis models, compared them against each other, and tested them against observations of white dwarf binaries from the Zwicky Transient Facility. This comparison showed that the actual Galactic population of these systems is significantly larger than one of the leading models had predicted, a result with direct consequences for the data analysis pipelines currently being developed for LISA.
