Fluorine in extremely hot post-AGB stars
Abstract
We have discovered lines of highly ionized fluorine (Fv and Fvi) in the far-UV spectra of extremely hot (Teff=85,000--150,000 K) post-AGB stars. Our sample comprises H-rich central stars of planetary nebulae as well as H-deficient PG1159 stars. We performed non-LTE calculations and find strong F overabundances (up to 10**-4 by mass, i.e., 250 times solar) in a number of PG1159 stars, while F is essentially solar in the H-rich stars. Since PG1159 stars are believed to exhibit intershell matter of the preceding AGB phase on their surface, their chemical analyses allow for a direct insight into nucleosynthesis processes during the AGB phase. The high F abundances in PG1159 stars confirm the conclusion from abundance determinations in giants, that F is synthesized in AGB stars and that the F enrichment in the intershell must be very high.
Keywords
Cite
@article{arxiv.astro-ph/0412258,
title = {Fluorine in extremely hot post-AGB stars},
author = {K. Werner and T. Rauch and J. W. Kruk},
journal= {arXiv preprint arXiv:astro-ph/0412258},
year = {2007}
}
Comments
Accepted for publication in A&A, 5 pages