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Дата индексирования: Mon Jun 28 04:04:06 2010
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OH/IR stars as the progenitors of planetary nebulae
 
P. te Lintel Hekkert and A.A. Zijlstra

Abstract

Based on a new sample of (IRAS based) OH/IR stars, and the catalogue of planetary nebulae compiled by Acker (1983), we study the relation between these two groups of objects, in terms of the kinematics and the Galactic distribution. In contrast with earlier analysis of samples of OH/IR stars and findings we find a close correlation between the kinematics of the planetary nebulae and the IRAS based sample of OH/IR stars. In particular, we find that the distribution of the planetary nebulae (PN) shows a good correlation with the OH/IR stars with low outflow velocity (\vexp\ $< 12.5 \kms$). Whether the high outflow velocity OH/IR stars also have a counterpart among PN is not clear. The majority of the known PN thus appear to originate from low outflow velocity OH/IR stars. The ZAMS progenitor star masses are probably in the range $1 \hbox{--} 1.5 \msolar$, and the stellar ages are $\approx 5 \hbox{--} 10 \times 10^9 \yr$. Only in the plane of the galaxy may a significant fraction of the PN come from more massive progenitors. In the outer part of the Galaxy, a relatively larger fraction of PN appears to originate from carbon stars instead of OH/IR stars. From a comparison between the expansion velocities of the OH/IR stars and PN, it is shown that for about $25\%$ of the PN the expansion velocity has increased significantly after the OH/IR star phase.

Keywords

OH/IR stars --- planetary nebulae --- stellar evolution