Measurements of the 12C/13C Ratio in Planetary Nebulae and Implications for Stellar Evolution |
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| Authors: | Palla F Galli D Bachiller R Pérez Gutiérrez M |
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| Institution: | (1) Osservatorio Astrofisico di Arcetri, L.go E. Fermi, 5 -, Firenze (, Italy;(2) Observatorio Astronómico Nacional Alcala de Henares (, Spain |
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| Abstract: | We present the results of a study aimed at determining the 12C/13C ratio in two samples of planetary nebulae (PNe) by means of mm-wave observations of 12CO and 13CO. The first group includes six PNe which have been observed in the 3He+ hyperfine transition; the other group consists of 23 nebulae with rich molecular envelopes. We have determined the isotopic ratio in 14 objects and the results indicate a range of values between 9 and 23. In particular, three PNe have ratios well below the value predicted by standard evolutionary models ( 20), indicating that some extra-mixing process has occurred in these stars. We briefly discuss the implications of our results for standard and nonstandard stellar nucleosynthesis. |
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| Keywords: | stars: abundances planetary nebulae: general radio lines: stars ISM |
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