Advanced evolutionary phase of a first-generation star |
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| Authors: | Dilhan Eryurt-Ezer |
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| Institution: | (1) Middle East Technical University, Ankara, Turkey |
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| Abstract: | The theoretical evolution of a first-generation star of 3M
 after the core helium-exhaustion phase has been investigated. The star displays the character of a double shell burning model. Shell hydrogenburning produces energy mostly by the p-p chain reaction. CN-cycle reaction is only operating in the inner edge regions where sufficient amount of carbon is formed by the 3 -reactions. Hence, the shell burning time of the star is longer than that of normal stars, thus lengthening the total evolutionary lifetime of the first-generation stars.Prior to carbon-burning phase, the mass of the complete hydrogen-exhausted region is 1.14M
and that of complete helium-exhausted region is 0.83M
. A carbon-oxygen core of about 0.87M
has developed within the star in which the ratio of carbon to oxygen is about 0.85, but decreases down to a value of 0.50 near the boundary of the core. |
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