In order to explain the lack of carbon stars in the Galactic bulge, we have made a detailed study of thermal pulseasymptotic giant branch （TP-AGB） stars by using a population synthesis code. The effects of the oxyge...In order to explain the lack of carbon stars in the Galactic bulge, we have made a detailed study of thermal pulseasymptotic giant branch （TP-AGB） stars by using a population synthesis code. The effects of the oxygen overabundance and the mass loss rate on the ratio of the number of carbon stars to that of oxygen stars in the Galactic bulge are discussed. We find that the oxygen overabundance which is about twice as large as that in the solar neighbourhood （close to the present observations） is insufficient to explain the rareness of carbon stars in the bulge. We suggest that the large mass loss rate may serve as a controlling factor in the ratio of the number of carbon stars to that of oxygen stars.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No 10647003)the Foundations of Xinjiang University,China (Grant Nos 070195 and BS060109)
文摘In order to explain the lack of carbon stars in the Galactic bulge, we have made a detailed study of thermal pulseasymptotic giant branch （TP-AGB） stars by using a population synthesis code. The effects of the oxygen overabundance and the mass loss rate on the ratio of the number of carbon stars to that of oxygen stars in the Galactic bulge are discussed. We find that the oxygen overabundance which is about twice as large as that in the solar neighbourhood （close to the present observations） is insufficient to explain the rareness of carbon stars in the bulge. We suggest that the large mass loss rate may serve as a controlling factor in the ratio of the number of carbon stars to that of oxygen stars.
