Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21725605s&link_type=abstract
American Astronomical Society, AAS Meeting #217, #256.05; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astrophysics
Scientific paper
The detection of neutron(n)-capture elements (atomic number Z>30) in the spectra of nearly 100 planetary nebulae (PNe; Sterling & Dinerstein 2008, ApJS, 174, 157) demonstrates that nebular spectroscopy is a potentially powerful new tool to investigate n-capture nucleosynthesis and the chemical evolution of trans-iron elements in the Universe. Nebular spectroscopy provides access to several n-capture elements that are not detectable in cool giant stars, and enables investigations of classes of stars and stages of evolution in which stellar photospheres are obscured by heavy mass loss. However, the poorly known atomic data for processes that govern the the ionization balance of n-capture elements present a major challenge to investigations of these species in ionized nebulae. These data are needed to accurately estimate the abundances of unobserved n-capture element ions, and hence to determine the total elemental abundances of these species.
To address this issue, we have computed photoionization cross sections and radiative and dielectronic recombination rate coefficients for low-charge ions of the three most widely observed n-capture elements in PNe (Se, Kr, and Xe). These results are benchmarked to experimental absolute photoionization cross sections measured at the Advanced Light Source synchrotron radiation facility. We also computed charge transfer rate coefficients for these species with a multichannel Landau-Zener code. These new atomic data will be incorporated into photoionization codes to derive reliable ionization corrections for Se, Kr, and Xe. We will apply these results to determine the abundances of n-capture elements in PNe to unprecedented accuracy, enabling robust investigations of s-process nucleosynthesis in PN progenitor stars.
NCS acknowledges support from an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-901432.
Aguilar Alejandro
Alna'Washi Ghassan
Bilodeau R. C.
David Kilcoyne A. L.
Esteves David Anthony
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