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 () 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 . 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.