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Session 44 - Circumstellar Material.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center
We present HST FOS spectroscopy of selected features in the system of ejecta from the star Eta Carinae during its mid-19th century outburst. These spectra, obtained in 1995 October, cover the wavelength range 1150-8000 Å\ in six gratings and utilize the 0.86 arcsec paired square apertures to isolate specific ejected features and nearby ``background" (2.6 arcsec away). This enables the first detailed study of the physical conditions of specific ejected material, compared to previous IUE and other spectra which were made with much larger apertures or poor spatial resolution. Our observations concentrate on three positions that were picked based on the excellent HST WFPC2 images released in early 1995: the ``Paddle" -a prominent knot in the circular ``disk" surrounding the star 3 arcsec SW of the star (which we call H2), (2) the brightest knot in the group that forms the ``S condensation'' in the ridge of material to the SW and outside of the homunculus (called S2), and (3) a more distant SW knot (outside the ridge, called S3) interesting in that it is the most outward knot in the SW ``counterjet" on the WFPC2 images. The FOS spectra are most notable in that they show a wealth of UV (and visual) emission lines which enable determination of the extinction, physical conditions (T_e amp; N_e), radial velocities, and abundances in the specific knots targeted. For example, the spectra of S2 amp; S3 show lines of five ionization states of nitrogen, ranging from N^\circ to N^+4, as well as the first detection of several carbon lines (e.g., C \sc iii]\lambda1909); but weak or no lines of expected oxygen ionization states. This further confirms that N/C and N/O in the ejecta are amazingly high. The spectra of the ``Paddle"(H2) are dominated by lines of Fe \sc ii, N \sc iii], C \sc iii], and Si \sc iii] that indicate a N_e in excess of 10^6 cm^-3; however, these spectra are contaminated by that of the background homunculus (which we are attempting to subtract using the ``offset" position spectra). We also discuss radial velocities and turbulence derived from various line widths. Supported in part by AURA/STScI grants related to GO-6042.
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