High-resolution 6450-24500 spectra of eta Carinae
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We discuss high-resolution (/ 3000-8600) spectra of the central knot or "star" in Car between 6450 and 24,500 , and of the Homunculus 7 southeast of the knot between 6450 and 9250 . A complete flux calibrated list of more than 170 emission lines is provided longward of 8780 , with additional measurements of the strongest forbidden lines and Fe II features down to 6700 . The generally strong N I and weak O I lines are consistent with an abundance mixture resulting from CNO burning in stellar envelopes, thus supporting the interpretation of Car as an evolved massive star. The continuum flux increased by a factor of 1.6 to 2.0 at 23,000 compared to recent measurements, but remained the same at 11,000 . This brightening and reddening of the IR continuum was accompanied by stronger H I and He I lines, constant or slightly weaker Fe II and [Fe II] lines, and increased extinction to AV 5m to 6m (from AV 3m.2 previously). The complex line profiles fall into two categories: (1) broad emission and sometimes blueshifted absorptions that form in a high-velocity wind reaching at least 700 km s-1, and (2) narrow emission cores that may be associated with a low-velocity (equatorial?) wind with speeds 100 km s-1. The broad lines in the Homunculus have profiles and equivalent widths similar to the broad components in the knot, but they are redshifted by 250 km s-1 due to rapid expansion of the reflecting dust. The reflected light spectrum of the Homunculus offers a better "view" of the high-velocity wind because it is free of the many strong narrow lines in the knot. For example, the Homunculus spectrum clearly shows lower velocity absorptions in O I 7773 compared to H I and He I, suggesting deceleration of the high-speed wind at large radii. The range of excitation in both the high- and low-velocity regions encompasses He I recombination and Fe II emission, but excludes the lower ionization required for Fe I, the CO band heads, and the infrared Ca II triplet, which are not detected. The narrow forbidden lines indicate densities in excess of the critical densities, ranging from 104 to nearly 107 cm-3. The narrow permitted lines are slightly broader than the forbidden lines and probably form in a denser region nearer the central star. All of the strongest Fe II lines at wavelengths 7000 , in both the broad and narrow-line regions, can be attributed to cascades from excited states that are "pumped" by resonant absorption of H I Ly. This process requires partially ionized gas and densities 105 cm-3.
