IAU PhD Prize for Dr Claude Cournoyer-Cloutier
The IAU has announced the winners of its annual PhD prizes, including MPA postdoc Claude Cournoyer-Cloutier, who was recognised for her thesis on the 'Dynamics and Feedback of Massive Binaries in Young Massive Star Clusters'.
Unlike our solitary Sun, most stars form in binaries within embedded star clusters. Massive stars almost always form in close binaries that undergo mass transfer, changing their subsequent evolution and how and when they return energy to their host galaxy, thereby regulating star formation. Furthermore, the cluster in which the stars form must also be considered, since stellar dynamics within dense star clusters can disrupt binaries or alter their orbits.
In her thesis, Dr Cournoyer-Cloutier used simulations involving hydrodynamics, star formation, stellar dynamics, and stellar evolution to study the interaction between binary stars and their host clusters during star cluster formation. She discovered that the larger-scale gas environment dominates cluster formation, naturally leading to fewer low- and intermediate-mass stars in binaries. This is consistent with the low binary fractions observed in older clusters. Massive stars, on the other hand, retain high binary fractions. Due to mass transfer, they return more energy to their environment than is predicted by standalone binary evolution models. Therefore, stellar dynamics and binary evolution play an essential role in understanding the formation of massive star clusters in galaxies.
The IAU Division H (Interstellar Matter and Local Universe) recognised the innovative nature of Cournoyer-Cloutier’s study. Each of the nine IAU divisions selects a winner and honourable mentions from candidates whose theses represent the most remarkable and impactful work in their field over the past year. The IAU PhD Prize is open to all early-career researchers. To recognise their achievements, the winners will be invited to present their work during the Division Days at the IAU XXXIII General Assembly, to be held in Rome, Italy, from 10–19 August 2027.
