AAS 205th Meeting, 9-13 January 2005
Session 20 Variability of Eta Carinae
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

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[20.02] The Presence of UV Molecular Absorptions at -513 km/s in the Ejecta Spectrum of Eta Car

K. E Nielsen (CUA & NASA/GSFC), T. R Gull (NASA/GSFC), G. Vieira Kober (SSAI & NASA/GSF), S. Ivarsson (CUA & NASA/GSFC), Eta Car HST Treasury Team

The blue-shifted absorption system at -513 km/s, seen in the spectrum of Eta Car, has been associated with the outer parts of the expanding Homunculus. The fast moving ejecta is primarily observed in spectra from neutral and singly ionized iron-group elements in addition to molecular lines particularly from H2. The atomic species show little or no variation in absorption as monitored with STIS across the 2003.5 minimum of Eta Car. By contrast, UV molecular absorption of H2 appear to change in line strength from the broad maximum into the several month long spectroscopic minimum. Over 800 absorption lines of H2 Lyman bands are observable at -513 km/s in the 1200-1600 Å{} portion of Eta Car's spectrum. The H2 transitions are from highly excited states (10\,000 to 30\,000 cm-1) and indicate an UV radiation dependent excitation. During Eta Car's spectroscopic minimum the absorption due to H2 weakens considerably, indicating a diminishing UV radiation field. In the NUV, spectral lines from CH and possible OH have been positively identified in the STIS spectrum. CH and OH are from very low energy states and increase, in contrast to H2, in absorption during the minimum. These observations were obtained through the STScI and ESO; funding was through STIS GTO and HST GO programs.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.