The relationship between two periodicities observed in Eta Carinae

An 85-day periodicity in the X-ray emission of Eta Cannae has been reported, while spectrocopic events recur with a period of 5.5 years (Corcoran et al., 1997 [Natur, 390, 587]; Damineli, 1996 [ApJ, 460, L49]). If the hot X-rays are produced by colliding winds in a 5.5-year binary system, then the interval of 85 days between X-ray flares is likely to represent pulsation or rotation of the primary star, or conceivably the orbit of a third object. In a broad class of models, the 85-day recurrence interval is predicted to lengthen drastically in 1998 after the two stars pass periastron. If this effect does occur, then it can give information about the nature of the system. If it does not, then specific types of models are ruled out.