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Paper: Infrared Spectroscopy of Neutron-Capture Elements in Planetary Nebulae
Volume: 313, Asymmetrical Planetary Nebulae III
Page: 410
Authors: Sterling, N.C.; Dinerstein, H.L.
Abstract: We present initial results from a survey of the neutron-capture elements Se (Z=34) and Kr (Z=36) in planetary nebulae (PNe). These elements are created in the s-process during the thermally-pulsing asymptotic giant branch (AGB) phase, and a PN may display heightened Se and Kr if third dredge-up (TDU) was efficient in the progenitor star. We have observed 27 PNe in the K band, and detected [Kr III] 2.199 and/or [Se IV] 2.287 μm in 12 of them. The high detection rate indicates that these lines are observable in a significant fraction of the Galactic PN population. We derive elemental abundances of Se and Kr by using the ionization correction factors Se3+/Se ≈ Ar++/Ar and Kr++/Kr ≈ S++/S, respectively, and find a wide range of Kr and Se abundances, from approximately solar to verabundant by a factor of ~5-10. This implies that the PN progenitors in our sample have a broad spectrum of dredge-up histories, from those that experienced no TDU to those in which it was quite efficient. We explore possible correlations between enrichment of neutron-capture elements and other nebular properties, such as C/O and N/O, but do not find significant relations at this early stage of our survey.
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