Long-term spectroscopy of eta Carinae - I. The high and low excitation phases

Quantitative measurements of line parameters in the spectrum of eta Carinae are presented for both the broad and narrow line components. A total of 65 5 spectral features were measured in the spectral range 3850 Angstrom to 11 000 Angstrom, giving a comprehensive view of the behavior of atomic transit ions ranging from a few to tens of electron volts. The spectrum on the phas e of maximum intensity in the high excitation lines (1995) is compared with that on minimum intensity (June 1992), showing that at this phase the high excitation Lines disappear but the broad components of low excitation line s strengthens. We reject a number of previous line identifications and prop ose several new ones, including Fe II, [Fe II], [Fe III], [N II], and the n ear-infrared Ca II triplet. Some lines commonly used to diagnose density, t emperature, chemical composition, and reddening were found to be blended, u rging a revision of the results based on previous data. The existence of do uble-peaked lines, suggested in previous papers, is ruled out. In the case of hydrogen lines, the apparent double-peaks are shown to be real absorptio n components. The velocity field in the inner 2 " around the central star s hows additional components previously unknown. The phases of high and low e xcitation in eta Carinae are discussed in light of a recently proposed bina ry system. We suggest a temperature T similar to 16000 K for the primary st ar, what indicates that it is close to the beginning of the core helium-bun ting evolutionary stage.