POSYDON is a next-generation single- and binary-star population synthesis framework, incorporating, fully self-consistent, state-of-the-art stellar structure and evolution modelling, using the MESA code, throughout the evolution of both binary components. This allows for a more accurate treatment of physical processes in stellar and binary evolution, including: realistic mass-transfer calculations and assessment of stability, internal angular-momentum transport and tides, stellar core sizes, mass-transfer rates, and orbital periods. The code is modular in many aspects and the user can specify initial population properties and adopt choices that determine how the evolution of a binary proceeds. Machine-learning methods are incorporated and applied on the grids of detailes single- and binary-star models for various classification and interpolation calculations, and the development of irregular grids guided by active learning, for computational efficiency.

POSYDON is being developed by a collaborative team of astrophysicists and computer scientists led by Principal Investigators Tassos Fragos (Université de Genève) and Vicky Kalogera (Northwestern University).

In Fragos et al. (2023), we describe the detailed methodology and implementation of POSYDON, including the assumed physics of stellar and binary evolution, the extensive grids of detailed single- and binary-star models, the postprocessing, classification, and interpolation methods we developed for use with the grids, and the treatment of evolutionary phases that are not based on precalculated grids.