Contributed Talk - Splinter Stars

Tuesday, 14 September 2021, 10:00   (virtual Stars)

Close stellar flybys are common in low-mass clusters

Amith Govind and Susanne Pfalzner
Forschungszentrum Jülich

Recent observations of protoplanetary discs show many with spiral arms in young low-mass clusters. A pattern analysis of some of them point to close flybys as being the most probable cause. Since flybys are expected to be rare in low-mass clusters, we re-examine the frequency of close flybys in low-mass clusters. We give importance to the fact that in the solar neighbourhood, low-mass clusters have smaller half-mass radii than high-mass ones. Hence, they can have mean and central densities comparable to high-mass clusters. We perform N-body simulations of stellar dynamics in young clusters obeying the observed mass-radius relation. We find that low-mass clusters can affect disc sizes just as much as, if not more than, high-mass clusters. Additionally, a significant number of small discs (< 30 au) are found in them. The primary conclusion is that close flybys cannot be neglected in low-mass clusters. As a testable prediction, we claim that 10%–15% of discs in low-mass clusters will be truncated by flybys to less than 30 au with a characteristic sharp outer edge.