Gravothermal oscillations in multicomponent models of star clusters

Abstract In this paper, gravothermal oscillations are investigated in multicomponent star clusters which have power-law initial mass functions (IMFs). For the power-law IMFs, the minimum masses (m min) were fixed and three different maximum stellar masses (m max) were used along with different power-law exponents (α) ranging from 0 to −2.35 (Salpeter). The critical number of stars at which gravothermal oscillations first appear with increasing N was found using the multicomponent gas code spedi. The total mass (M tot) is seen to give an approximate stability condition for power-law IMFs with fixed values of m max and m min independent of α. The value M tot/m max ≃ 12 000 is shown to give an approximate stability condition which is also independent of m max, though the critical value is somewhat higher for the steepest IMF that was studied. For appropriately chosen cases, direct N-body runs were carried out in order to check the results obtained from spedi. Finally, evidence of the gravothermal nature of the oscillations found in the N-body runs is presented.