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Evolutionary connection between C-rich AGB stars and C-rich central stars of PNe

Published online by Cambridge University Press:  25 May 2016

M. Parthasarathy
M. Parthasarathy*
Affiliation:
Indian Institute of Astrophysics, Bangalore - 560034, India

Abstract

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On the basis of C/O ratios the evolutionary connection between C-rich AGB/post-AGB stars and C-rich central stars of PNe is discussed. The proportion of carbon-rich post-AGB stars is comparable to that of carbon-rich PNe. The post-AGB stars with 21μm emission are found to be over abundant in carbon and s-process elements indicating that they have gone through the third dredge-up and carbon star phase on the AGB. As these stars evolve to higher temperature they will form carbon-rich PNe with carbon-rich central stars. Analysis of C/O ratios of PNe suggests that 68 percent of PNe have C/O > 1 indicating that the progenitors have gone through the third dredge-up and carbon-rich phase on the AGB. The Type I PNe can be divided into two groups. Group I Type I PNe are those with C/O < 1 indicating that their massive progenitors have gone through the third dredge-up and hot bottom burning on the AGB. Group II Type I PNe are those with C/O > 1. Their progenitors have gone through third dredge-up only and may not have experienced hot bottom burning. Carbon stars with silicate dust and or carbon-rich post-AGB stars (such as post-AGB stars with 21μm emission) may be the progenitors of PNe with [WC] central stars. The evolutionary sequence seems to be: carbon-rich AGB → carbon-rich post-AGB → [WC late type] → [WC early type] → [WC-PG 1159] → PG 1159.

Type
Part 5. Non-Spherical Mass Loss, Binarity, Post-AGB Evolution
Information
Symposium - International Astronomical Union , Volume 191: Asymptotic Giant Branch Stars , 1999 , pp. 475 - 480
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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