Using the high dispersion NUV mode of the Space Telescope Imaging Spectrograph ( STIS ) aboard the Hubble Space Telescope ( HST ) to observe Eta Carinae , we have resolved and identified over 500 sharp , circumstellar absorption lines of iron-group singly-ionized and neutral elements with \approx 20 velocity components ranging from - 146 km s ^ { -1 } to - 585 km s ^ { -1 } .
These lines are from transitions originating from ground and metastable levels as high as 40,000 cm ^ { -1 } above ground .
The absorbing material is located either in dense inhomogeneities in the stellar wind , the warm circumstellar gas immediately in the vicinity of Eta Carinae , or within the cooler foreground lobe of the Homunculus .
We have used classical curve-of-growth analysis to derive atomic level populations for Fe ii at - 146 km s ^ { -1 } and for Ti ii at - 513 km s ^ { -1 } .
These populations , plus photoionization and statistical equilibrium modeling , provide electron temperatures , T _ { \mathrm { e } } , densities , n _ { \mathrm { H } } , and constraints on distances from the stellar source , r. For the - 146 km s ^ { -1 } component , we derive T _ { \mathrm { e } } = 6400 K , n _ { \mathrm { H } } \geq 10 ^ { 7 } - 10 ^ { 8 } cm ^ { -3 } , and d \approx 1300 AU .
For the - 513 km s ^ { -1 } component , we find a much cooler temperature , T _ { \mathrm { e } } = 760 K , with n _ { \mathrm { H } } \geq 10 ^ { 7 } cm ^ { -3 } , we estimate d \approx 10,000 AU .
The large distances for these two components place the absorptions in the vicinity of identifiable ejecta from historical events , not near or in the dense wind of \eta Car .
Further analysis , in parallel with obtaining improved experimental and theoretical atomic data , is underway to determine what physical mechanisms and elemental abundances can explain the large number of strong circumstellar absorption features in the spectrum of \eta Car .