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| Paper: |
Cosmochronology in Action: Determination of the Mean Core
Composition of the White Dwarfs in M 67 |
| Volume: |
469, 18th European White Dwarf Workshop (EUROWD12) |
| Page: |
201 |
| Authors: |
Simon, A.; Fontaine, G.; Brassard, P. |
| Abstract: |
As the rate of helium thermonuclear burning in stars remains uncertain,
the exact proportions of carbon and oxygen in the cores of white dwarfs
are still unknown. Given that the cooling time depends on such proportions,
the luminosity functions for populations of white dwarfs with various
compositions are not be the same. By comparing theoretical luminosity
functions computed for populations of white dwarfs with different ratios
of carbon and oxygen with the observed luminosity function of M 67 — a
star cluster for which we have a precise knowledge of its age — we are
able to infer the mean ratio of carbon-to-oxygen in the white dwarfs in
that system. To obtain the theoretical luminosity functions, we
computed some 100 state-of-the-art evolutionary sequences and combined
the results with models of the stellar formation rate, the
initial-to-final mass relationship, and the initial mass function. Under the
assumption that the M 67 white dwarfs are all DA's with standard
“thick” envelopes, we infer that the cores of these white dwarfs are
dominated by oxygen. |
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