ETA-CARINAE - A LONG-PERIOD BINARY

We present new observations of eta Carinae, strongly suggesting that i t is a binary system. High dispersion measurements of the broad Pay em ission line show periodic radial velocity variations that are nicely e xplained by a star in a highly eccentric orbit. Velocity characteristi cs of the system imply massive components, in accord with the luminosi ty and spectral characteristics. Strong and variable wind-wind interac tions are predicted to take place in eta Car on the basis of the orbit al elements and physical characteristics of the components. The low ex citation event predicted for the end of 1997 is underway, confirming t he high coherence of the 5.52 year cycle and adding confidence to eta Car as a binary system. We associate this event with periastron passag e. A conclusive demonstration of the binary orbit is still pending, bu t the present work has the advantages of bringing this mysterious obje ct within a stellar evolution framework, and, for the first time in it s history, predictions suitable for testing against future observation s. (C) 1997 Elsevier Science B.V.