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G.V. Kober (SSAI & GSFC/NASA/EUD), T.R. Gull (GSFC/NASA/EUD), K. Nielsen, F. Bruhweiler (CUA & GSFC/NASA/EUD), K. Verner (UDC & CUA & GSFC/NASA/EUD), O. Stahl (U. Heidelberg), K. Weis, D. Bomans (U. Bochum)
We are measuring relative elemental abundances for the ejecta in the line of sight from Eta Carinae using high dispersion spectroscopy with the HST/STIS and the VLT/UVES. While multiple velocity components have been identified, we focus on the -513 and -146 km/s components originating from the Homunculus and the Little Homunculus.
Complicating factors are the complex nebular structures in the immediate vicinity of the bright, massive star: the very bright emission structures, Weigelt blobs B, C and D, the broad, clumpy structures of the extended wind apparently not photoionized by Eta Car B, and general scattered starlight from the extended wind and the dusty core of the circumstellar material.
We have used the 3050 to 3160A region of overlap between STIS and UVES to intercompare equivalent widths of absorption lines to estimate the 'contributing factor', namely the amount of light originating from the star compared to nebular structures. While the extracted STIS spectra are from 0.1" wide aperture, the UVES spectra are limited by the 1" seeing conditions. Curiously we find that the scattering contribution in the UVES spectra changes with time, apparently with orbital phase of the 5.54-year period. This indicates that the dust may be modified by changes in the central source with phase. The noticeable drop in scattered light appears to occur about 1.7 years (phase 0.35) after the spectroscopic minimum.
Relative abundances of iron peak elements and some molecules will be estimated.
Observations in this study were accomplished with HST through STScI and with VLT through ESO and funded under STIS GTO resources.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.