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Title: | Evolutionary connection between C-rich AGB stars and C-rich central stars of PNe |
Authors: | Parthasarathy, M |
Keywords: | Post-Agb Stars Red Giant Stars Planetary Nebulae Carban- rich PNe |
Issue Date: | 1999 |
Publisher: | International Astronomical Union |
Citation: | IAU Symposia, Vol. 191, pp. 475 - 480 |
Abstract: | 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 21 micron 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 21 micron 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. |
URI: | http://hdl.handle.net/2248/2815 |
ISSN: | 0074-1809 |
Appears in Collections: | IIAP Publications |
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