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G. M. Wahlgren (CUA/Lund), S. Ivarsson, S. Johansson (Lund), C. R. Proffitt (CUA/STScI), S. J. Adelman (The Citadel), J. Rice, A. F. Gulliver (Brandon Univ.), G. Hill (Keck Obs.), D. S. Leckrone (NASA/GSFC), D. P. Smith (UNLV)
We report on progress made in our Far Ultraviolet Spectroscopic Explorer (FUSE) program (ID A130; PI J.Rice) that pertains to understanding the absorption line spectrum of the magnetic chemically peculiar B star 17 Com A (HD108662). Spectral observations were made on ten occasions with the FUSE observatory over a five day interval in April 2001 for the purpose of studying temporal flux variations over the stellar rotational period of 5.07 days. These data will allow us to correlate the far-UV flux variations with elemental abundance variations over the stellar surface as mapped out by optical Doppler image mapping techniques. Complementing the FUSE data are high-resolution optical spectra obtained at the Nordic Optical Telescope and the McDonald Observatory. From the optical spectra we have determined the rotational velocity (v sin i = 17 km s-1) and chemical abundances. The iron-group elements are generally enriched by a factor of 10 relative to the solar values and as such, are responsible for a large part of the line absorption in the FUSE spectral region. Using synthetic spectrum techniques with the abundances derived from the optical region data and FUSE archival spectra of normal and non-magnetic CP stars, we can identify approximately two-thirds of the absorption features in the FUSE spectrum of 17 Com A. In particular, we have concentrated on contributions from the Cr II/III and Fe II/III spectra. Aspects of atomic spectroscopy are also being carried out with the FUSE spectra. New experimental oscillator strengths for 4d-4f transitions of Fe II observed at optical wavelengths are used in conjunction with the FUSE spectra of chemically normal B type stars to determine oscillator strengths for important Fe II 3d-4f transitions.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.