Specific entropy and the evolution of unconfined stellar systems
Abstract
The time rate of change in number, energy, and entropy appropriate for a globular cluster described initially by a King model is examined, with attention focused on analytic expressions for changes (losses) in number density, energy density and entropy density. These expressions are valid in the limit that the local escape velocity is much greater or much less than the rms velocity of the cluster as a whole. Asymptotic expressions for these losses were calculated for an initial King distribution resulting from evaporation induced by interstellar collisions that may be modeled by a FokkerPlank (or Landau) equation. These loss rates were then used to evaluate characteristic time scales. It was found that number density and entropy density decrease with time. Of particular interest was the behavior of the specific entropy (entropy density/number density). Near the edge of the system, the specific entropy was constant to leading order, while in the limit of large escape velocities, specific entropy decreased with time. It is concluded that losses due to evaporation exceed gains resulting from lack of thermalizataion.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 1986
 Bibcode:
 1986A&A...157..387K
 Keywords:

 Entropy;
 Globular Clusters;
 Star Clusters;
 Stellar Systems;
 Evaporation;
 Evolution (Development);
 FokkerPlanck Equation;
 Vlasov Equations;
 Astrophysics