2004/08/25 by N. C. Sterling, Sterling, N. C., H. L. Dinerstein +1
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0408481
4 pages, to appear in "Cosmic Abundances as Records of Stellar Evolution and Nucleosynthesis", ASP Conf. Ser., ed. T. Barnes and F. Bash
arxiv created 2004/08/25 · arxiv updated 2009/12/01
We present results from an ongoing survey of infrared emission lines from the neutron-capture elements Se and Kr in Galactic planetary nebulae (PNe). Se and Kr may be produced in the initial steps of the s-process during the asymptotic giant branch (AGB) phase of PN progenitor stars, and brought to the surface by convective dredge-up before PN ejection. Therefore, enriched Se and Kr abundances in PNe indicate that the s-process and dredge-up were active within the progenitor stars. We have detected the emission lines [Kr III] 2.199 and [Se IV] 2.287 microns in 68 of 119 Galactic PNe, and used these line fluxes to derive ionic and total elemental abundances. Using the ionization correction factors Se3+/Se = Ar++/Ar and Kr++/Kr = S++/S, we find a range of Se and Kr abundances, from nearly solar to enriched by a factor of 5-10 times, which implies varying degrees of dredge-up efficiency in the progenitor stars. We have searched for correlations between n-capture element abundances and other nebular properties, and find that PNe with Wolf-Rayet central stars tend to exhibit more elevated Se and Kr abundances than other nebulae. Bipolar nebulae, believed to arise from the most massive of PN progenitors, may have lower n-capture abundances than elliptical PNe.