AAS 200th meeting, Albuquerque, NM, June 2002
Session 74. Stellar Atmospheres and Circumstellar Material
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

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[74.10] Nebular Absorption lines seen in the Near Ultraviolet Spectrum of Eta Carinae

G. Vieira (SSAI, NASA's GSFC), A. Danks (L3-Analytics, NASA's GSFC), T. R. Gull (NASA's GSFC)

Using the Space Telescope Imaging Spectrograph in the echelle mode, E230H, with a resolving power, R~130,000, we have observed the Central Source of Eta Carinae in the spectral region from 2350 to 3160A. Over 500 absorption lines have been identified as originating from FeI, FeII, TiII, VII, NiII, CoII, MnII and MgII. Most of the lines have multiple components with velocities ranging from -145 to -587 km/s. We also see the many interstellar absorption velocity systems known to exist in the direction of other Carinae stars. The ISM absorption lines usually originate from the ground level; many of the nebular absorption lines originate from levels well above the ground state. While the nebular absorption lines are complex in nature, we are able to sort out much information by cross-comparison of the strongest absorbed lines down to the weakest absorption lines. The predominant velocity systems are at -145km/s and -513km/s. The -145km/s system exhibits relatively broad absorption profiles and the lower levels are typically well above the ground state, even as much as 45000cm-1. The -513km/s system conversely has very narrow absorption profiles, with most lines originating from elevated spin-orbit levels in the ground state. The -513km/s system includes many TiII and VII lines. To our knowledge, this is the first detection of VII in nebular or interstellar absorption systems.

Thus far, we have focused on line identifications and velocity systems. We are gathering information on measured and theoretical oscillator strengths in preparation to measure the physical properties of these velocity systems and possibly relative elemental abundances.

This work is supported by STIS GTO funding, STScI and the HST Project.

The author(s) of this abstract have provided an email address for comments about the abstract: gull@sea.gsfc.nasa.gov

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.