AAS 204th Meeting, June 2004
Session 7 A Walk Through the HR Diagram
Poster, Monday, May 31, 2004, 9:20am-6:30pm, Ballroom

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[7.08] Modelling Stellar Optical and Mid-Ultraviolet Spectra from First Principles

R.C. Peterson (Astroph.Adv. & UCO/Lick), B.W. Carney (UNC), B. Dorman (L-3Com), E.M. Green (Steward Obs.), W. Landsman (SSA,Inc.), J. Liebert (Steward Obs.), R.W. O'Connell, R.T. Rood, R.P. Schiavon (UVa)

We present comparisons of theoretical and observational high-resolution spectra for a half-dozen stars of a wide range of temperature and abundance, from A star to K giant. These show the fits achieved to date by our ab initio spectral calculations. These comparisons form the first phase of our three-year Hubble Treasury program GO-9455/9974, aimed at providing mid-ultraviolet spectral templates to improve the determination of the age and metallicity of old stellar systems. From matches such as these, we have modified the input atomic-line parameters and guessed the identifications of spectral lines missing from the calculations, as described by Peterson, Dorman, & Rood (2001, ApJ, 559, 372).

With this new line list, we now match well the optical spectra of stars of all line strengths. We have begun to calculate a grid of optical indices from the theoretical spectra. In the mid-UV, while the fits at solar abundance are much improved, we are still missing very weak absorption lines near 2650Åand 2900Å. This will be addressed as additional mid-ultraviolet spectra are taken for a larger range of stellar targets during Cycle 13.

Support for this work includes grants GO-9455 and GO-9974 from the Hubble Space Telescope Science Institute, and an award from the NASA-OSS Long Term Space Astrophysics program.

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