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B. Sharpee (SRI International), E. Pellegrini, J.A. Baldwin (Michigan State University), R. Williams (STScI), P.A.M. van Hoof (Queen's University of Belfast)
The ground-breaking spectra of the planetary nebula NGC 7027 taken by Pequignot and Balteau (A&A, 283, 1994) revealed for the first time optical emission lines from Z>30 s- and r-process elements in a planetary nebula. Abundances determined from s-process element lines confirmed that the slow neutron capture process is extremely efficient during the nebular precursor's AGB phase. However, the abundance of the predominately r-process produced element Xe, at nearly the same enrichment as the more s-process produced element Kr, was unexpected due to the assumed low mass progenitor of the nebula. We present here preliminary results from follow up observations of NGC 7027 taken with the KPNO 4 meter echelle spectrograph. Spectra were taken over 4 nights in the range 4600--9950Åat a higher resolution (R=15000) and with a higher sensitivity than the Pequignot and Balteau spectra in order to bring out their weakest emission lines. We have applied our automated emission line identification code EMILI (Sharpee et al., ApJS, 149, 2003) and extended it to elements Z>30 in order to confirm the identifications of s- and r-process lines identified by Pequignot and Balteau.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.