Resolving the X-ray Variability of the Supermassive Star Eta Carinae

ROSAT, ASCA, RXTE and now Chandra X-ray observations of the supermassive star Eta Carinae obtained over the past 7 years chronicle the inordinate variability of the high-energy emission. The most important characteristics are these: 1) the hard X-ray ``low state" evidently recurs with a period consistent with the ``Damineli Cycle" of 5.5 years; 2) the X-ray emission exhibits ``flares" which occur quasi-periodically; 3) the overall X-ray brightness in the current ``cycle" is brighter than at the same phase in the last cycle; 4) the hard, variable ``core" source is apparently resolvable at lower energies but unresolvable at energies above 4 keV. The X-ray data appear consistent with a model of X-ray generation via colliding winds in a massive binary system coupled with dust scattering, though the ``flaring" activity probably requires that the wind from at least one of the stars is azimuthally structured. It is difficult to account for all the X-ray properties by activity in a single star. This work has been funded by NASA.