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T. Gull (Goddard Space Flight Center), T. Zethson, H. Hartman, S. Johansson (Lund University), K. Davidson (University of Minnesota), K. Ishibashi (NASA NAS/NRC, Goddard Space Flight Center)
Observations with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope reveal a peculiar emission line region in the close vicinity to Eta Carinae. The lines of [SrII], [MnII], [CoII], [TiII], [NiII] and [FeI] are detected in the 6400-7000A spectral interval at a blue-shifted velocity of ~95 km/sec and seem to be associated with a long, narrow filament with dimensions of <0.5" by 1.1". The filament is notable as it is separate both in velocity and structure from the bright emission of the Integral Nebula. This filament is buried within the Homunculus and is not visible in direct images which are dominated by reflection nebulosities. In our literature searches we have found no evidence of strontium emission lines in nebulae. We are aware of permitted transitions of strontium seen in AGB stars. S-processed elements like strontium are not expected in the ejecta of a massive star like Eta Carinae. Detection of [SrII] and the fact that the [NiII], [MnII] and [CoII] lines are unusually strong compared to [FeI] are quite a surprise. It has long been known that nitrogen is overabundant in the ejecta of Eta Carinae. Is this processed material from the present star(s)? Has there been processed material ejected from a more evolved companion? The situation is decidedly mysterious. This research has been supported by NASA through STScI grants and the STIS GTO funding.
The author(s) of this abstract have provided an email address for comments about the abstract: gull@sea.gsfc.nasa.gov