Collisional fragmentation and bulk composition tracking in REBOUND

Abstract

We present a fragmentation module and a composition tracking code for the 𝑛-body code . Our fragmentation code utilises previous semi-analytic models and follows an implementation method similar to fragmentation for the 𝑛-body code . In our 𝑛-body simulations with fragmentation, we decrease the collision and planet formation timescales by inflating the particle radii by an expansion factor 𝑓 and experiment with various values of 𝑓 to understand how expansion factors affect the collision history and final planetary system. As the expansion factor increases, so do the rate of mergers which produces planetary systems with more planets and planets at larger orbits. Additionally, we present a composition tracking code which follows the compositional change of homogeneous bodies as a function of mass exchange and use it to study how fragmentation and the use of an expansion factor affects volatile delivery to the inner terrestrial disc. We find that fragmentation enhances radial mixing relative to perfect merging and that on average, as 𝑓 increases so does the average water mass fraction of the planets. Radial mixing decreases with increasing 𝑓 as collisions happen early on, before the bodies have time to grow to excited orbits and move away from their original location.

Misalignment of terrestrial circumbinary planets as an indicator of their formation mechanism

“…Doing so decreases the collision time which, when collisions are modeled as only perfect mergers, quickly decreases the number of bodies in the system and reduces the computation time. Although a large expansion factor may lead to somewhat different system architectures, the general planet formation trends that emerge are similar to those found in simulations with lower values of f (Childs & Martin 2021a;Childs & Steffen 2022).…”