Neutron-Capture Elements in Planetary Nebulae: Identification of Two Near-Infrared Emission Lines as [KR III] and [SE IV]

Details Neutron-Capture Elements in Planetary Nebulae: Identification of Two Near-Infrared Emission Lines as [KR III] and [SE IV] Neutron-Capture Elements in Planetary Nebulae: Identification of Two Near-Infrared Emission Lines as [KR III] and [SE IV]

Apr 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001apj...550l.223d&link_type=abstract

The Astrophysical Journal, Volume 550, Issue 2, pp. L223-L226.

Astronomy and Astrophysics

Astronomy

42

Infrared: Ism, Ism: Lines And Bands, Line: Identification, Ism: Planetary Nebulae: General, Ism: Planetary Nebulae: Individual: Alphanumeric: Ic 5117, Ism: Planetary Nebulae: Individual: Ngc Number: Ngc 7027, Stars: Agb And Post-Agb

Scientific paper

I propose that two previously unidentified lines at 2.199 and 2.287 μm seen in the spectra of planetary nebulae (PNs) are fine-structure transitions of Kr+2 and Se+3. These are the cosmically most abundant elements with Z>32. The ionic stages and originating energy levels of the observed transitions are expected to be significantly populated under nebular conditions, and these elements-especially the noble gas Kr-are unlikely to be strongly depleted out of the gas phase into grains. Furthermore, their concentrations can be enhanced by s-processing, which occurs in the interiors of the PN progenitor stars. The observed line strengths are consistent with modest (factor of a few) overabundances. In support of the identification of the 2.199 μm line as [Kr III] 3P1-3P2, PNs that display this line also show [Kr III] 1D2-3P2 6828 Å emission. I identify the 2.287 μm line as [Se IV] 2P3/2-2P1/2. These identifications suggest a new range of possibilities for line identifications in the infrared. In addition, the observability of emission lines from n-capture species introduces a novel approach for studying advanced evolutionary stages and nucleosynthesis in the progenitor stars and for more fully delineating the role of PNs as agents of galactic chemical enrichment.

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