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| Paper: |
Determination of the Core Composition of White Dwarfs in M67 |
| Volume: |
493, 19th European Workshop on White Dwarfs |
| Page: |
137 |
| Authors: |
Simon, A.; Fontaine, G.; Brassard, P. |
| Abstract: |
Since stellar helium thermonuclear burning is still not well
constrained, the exact proportion of carbon and oxygen in the core of
white dwarfs remains largely unknown. Given that the cooling time of
these objects depends on their composition, it is thus crucial to
constrain the latter in order to use white dwarfs as
cosmochronometers. To address this, we compared theoretical luminosty
functions built for a wide range of compositions to the observed
luminosity function of the coeval white dwarfs in the M67
cluster. Theoretical luminosity functions were determined from 300
state-of-the-art evolutionary sequences, combined with models for the
stellar formation rate, initial mass function, and initial-to-final mass
relationship. Since the age of M67 is known to a good precision , this
comparison allowed us to determine the mean carbon-to-oxygen ratio of
its white dwarf population. Assuming that the white dwarfs in M67 are
80% DA's and 20% DB's with standard "thick" envelopes, we find that
their core composition is dominated by oxygen. |
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