The effects of stellar population synthesis on the distributions of the asteroseismic observables {\nu}_max and {\Delta}{\nu} of red-clump stars

Abstract

The distributions of the frequencies of the maximum oscillation Power ({\nu}_max) and the large frequency separation ( {\Delta}{\nu}) of red giant stars observed by CoRoT have a dominant peak. Miglio et al. (2009) identified that the stars are red-clump stars. Using stellar population synthesis method, we studied the effects of Reimers mass loss, binary interactions, star formation rate and the mixing-length parameter on the distributions of the {\nu}_max and {\Delta}{\nu} of red-clump stars. The Reimers mass loss can result in an increase in the {\nu}_max and {\Delta}{\nu} of old population which lost a considerable amount of mass. However, it leads to a small decrease in those of middle-age population which lost a little bit of mass. Furthermore, a high mass-loss rate impedes the low-mass and low-metal stars evolving into core-helium burning (CHeB) stage. Both Reimers mass loss and star formation rate mainly affect the number of CHeB stars with {\nu}_max and {\Delta}{\nu}, but hardly affect the peak locations of {\nu}_max and {\Delta}{\nu}. Binary interactions also can lead to an increase or decrease in the {\nu}_max and {\Delta}{\nu} of some stars. However, the fraction of CHeB stars undergoing binary interactions is very small in our simulations. Therefore, the peak locations are also not affected by binary interactions. The non-uniform distributions of {\nu}_max and {\Delta}{\nu} are mainly caused by the most of red-clump stars having an approximate radius rather than mass. The radius of red-clump stars decreases with increasing the mixing-length parameter. The peak locations of {\nu}_max and {\Delta}{\nu} can, thus, be affected by the mixing-length parameter.