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The diffusive overshooting approach on Li abundance in clusters | Q. S. Zhang
; | Date: |
5 Sep 2012 | Abstract: | The helioseimic investigation shows that the convective overshooting can
penetrate $0.37H_P$ to the location where the temperature is $2.5 imes10^6 K$
which is the typical temperature of the reaction $Li^7(p,alpha)He^4$. This
indicates that the overshooting mixing should be involved in investigating the
solar Li abundance problem. Observations of Li abundance of solar-twins show
that the sun is not very peculiar. The overshooting mixing should be also
involved in investigating Li abundance in clusters. However, the fully
overshooting mixing with the length of $0.37H_P$ results in too much Li
depletion to fit the observation in the solar case. Therefore, using the
diffusive process to describe the overshooting is more suitable. The diffusive
overshooting approach requires the turbulent r.m.s. velocity in the
overshooting region to calculate the diffusion coefficient. Turbulent
convection models(TCMs), which are suggested by helioseimic investigation, can
provide the turbulent properties in the overshooting region. However, TCMs are
often too complex to be applied in the calculations of the stellar evolution.
It is an easier way to use the asymptotic solution of TCMs. In this paper, I
use the asymptotic solution of Li & Yang’s TCM, which results in agreements in
both solar sound speed and solar Li abundance, to investigate Li abundance in
clusters(Hyades, Praesepe, NGC6633, NGC752, NGC3680 & M67). It is found that
the overshooting mixing leads to significant Li depletion in the old
clusters($t>1Gyr$) and little effect in the young clusters($t<1Gyr$). | Source: | arXiv, 1209.0977 | Services: | Forum | Review | PDF | Favorites |
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