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| Paper: |
Core-``Overshooting'' and the Distribution of Giants in the HRD |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
856 |
| Authors: |
Schroder, K.-P. |
| Abstract: |
We derived a set of apparently single stars with d <= 50 pc and Mv brighter than 4m from the newly available Hipparcos Catalogue, which can be regarded as an (almost) complete, volume-limited sample of single stars in the solar neighbourhood. We compare the HRD of this sample (Fig. 1) to theoretical stellar distributions in the HRD (Figs. 2 to 4), which are based on three grids of evolutionary tracks of different ``overshoot'' parameterization. For the mass range of 1.3 to 5 M_odot we first determine the present day mass function (PDMF) for each case. We then analyze how the distribution of stars and giants depends on the ``overshooting''. We find that the distribution of the real stars can be matched remarkably well with the same parameterization of ``overshooting'' which we obtained from modelling eclipsing binaries in the mass range of 2.5 to 7 M_odot, plus a decline of the overshoot between 2.5 and 1.6 M_odot. For the latter star-rich mass range, we here present a new sensitive test: the population of the lower Hertzsprung gap. It allows us to precisely specify the stellar evolution on the AGB, including the upper mass limit of giants starting into the AGB with a He-flash, forming the ``K giant clump''. A simulation of the HRD on the basis of that grid (Fig. 4) yields a (preliminary) initial (single star) mass function IMF propto Mstar^{1.2} and a quantification of the distribution and masses of giants over the GB, K giant clump, blue loops, AGB and cool wind domain. Our results are of relevance to various astrophysical problems such as, e.g., the evolution of stellar activity or the galactic dust and gas injection rate. |
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