Posidonius is a N-body code based on the tidal model used in Mercury-T (ascl:1511.020). It uses the REBOUND (ascl:1110.016) symplectic integrator WHFast to compute the evolution of positions and velocities, which is also combined with a midpoint integrator to calculate the spin evolution in a consistent way. As Mercury-T, Posidonius takes into account tidal forces, rotational-flattening effects and general relativity corrections. It also includes different evolution models for FGKML stars and gaseous planets. The N-Body code is written in Rust; a Python package is provided to easily define simulation cases in JSON format, which is readable by the Posidonius integrator.

Mercury-T calculates the evolution of semi-major axis, eccentricity, inclination, rotation period and obliquity of the planets as well as the rotation period evolution of the host body; it is based on the N-body code Mercury (Chambers 1999, ascl:1201.008). It is flexible, allowing computation of the tidal evolution of systems orbiting any non-evolving object (if its mass, radius, dissipation factor and rotation period are known), but also evolving brown dwarfs (BDs) of mass between 0.01 and 0.08 M⊙, an evolving M-dwarf of 0.1 M⊙, an evolving Sun-like star, and an evolving Jupiter.