Fluid sorting method for stellar collisions:

On-line software.

If the relative velocity at infinity, V_rel, is lower than the stellar escape velocity, V_star (of order 500-1000 km/s), which is the case for collisions happening in open or globular clusters, the relative velocity at contact is similar to the thermal velocity of stellar matter. Hence, such collisions are only mildly supersonic and entropy is nearly conserved. Consequently, the structure of the merger can be established by sorting the mass elements from the parent stars according to their entropy, as demonstrated by Lombardi and his collaborators (Lombardi et. al. 2002).

Make Me A Star (MMAS) is a freeely available software package that quickly generates collision product models for such scenarios. MMAS implements fast fluid-sorting algorithms to treat nearly parabolic encounters between low-mass main sequence stars, including an approximate treatment of mass loss and shock heating. This software is intended to be used in combination with realistic dynamical simulations of star clusters. MMAS is currently being implemented as the hydrodynamics module of two on-line programs that unite stellar dynamics, hydrodynamics and evolution: