X-ray emission and variability of η Carinae

We review the X-ray properties of the supermassive LBV 97 Carinae, and briefly compare the X-ray observations of eta Carinae with P Cygni, another "canonical" LBV. In the rest of this paper we try to fit the RXTE light curve with a colliding-wind emission model to refine the ground-based orbital elements. Our X-ray light curve modelling suggests that the mass-loss rate from eta Carinae is generally less than 3 x 10(-4) M-circle * yr(-1), about a factor of 5 lower than that derived from some observations in other wavebands. We could not match the duration of the X-ray minimum with any colliding-wind model in which the wind is spherically symmetric and the mass-loss rate is constant. However, we show that we can match the variations around X-ray minimum if we include an increase of a factor of similar to 20 in the mass-loss rate from eta Carinae for approximately 80 days following periastron. Based on the X-ray fluxes, the distance to eta Carinae is 2300 pc with formal uncertainties of only similar to 10%.