Modeling Massive Stars and the Need for Atomic Data
Abstract
With the advent of fast computers and new techniques it is feasible to compute sophisticated non-LTE models for A and OB Stars, Luminous Blue Variables, Wolf-Rayet stars, and supernovae. However, in many cases a lack of reliable atomic data is limiting the accuracy of results that can be achieved. For example, uncertainties in the bound-bound collisional rates for hydrogen limit the accuracy with which log g, and hence stellar masses, can be determined. For elements, such as Fe IV and O III, accurate wavelengths of important transitions are not known. The absence of accurate Fe IV wavelengths, for example, significantly affects the quality of spectral synthesis in the UV. In addition, codes such as CMFGEN (Hillier and Miller 1998) predict observable optical Fe IV transitions but the wavelengths of such lines are not known. Accurate wavelengths are important for obtaining Fe abundances from optical spectra, without the need for UV spectra, and also for determining blends which could influence other abundance determinations. While there have been substantial improvements in the availability of oscillator strengths and photoionization cross-sections, important data are still lacking. In particular, data for fine structure lines for levels where departures from LS coupling are important, and collisional data for many species, are unavailable.
- Publication:
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American Astronomical Society Meeting Abstracts #212
- Pub Date:
- September 2008
- Bibcode:
- 2008AAS...212.0345H