Post-collapse evolution and gravothermal oscillation of globular clusters

Post-collapse evolution of globular clusters is studied by means of a gaseous model. As a result of the gravothermal instability, cores of globular clusters have been thought to collapse within a finite time. It is shown that there exists a gravothermally unstable isothermal configuration with a central singularity of a definite functional form. Evolution towards such a configuration is computed numerically. Here, however, energy release through hardening of binary stars is taken into account. It is found that the globular cluster does not approach it monotonically but oscillatorily. The core oscillates between a state with a high-density cusp at the centre and another state having a regular isothermal core of moderate central density. (author)