We report the results of an observing campaign on Car around the 2003 X-ray minimum, mainly using the XMMNewton observatory. These are the first spatially resolved X-ray monitoring observations of the stellar X-ray spectrum during the minimum. The hard X-ray emission, associated with the wind-wind collision (WWC) in the binary system, varied strongly in flux on timescales of days, but not significantly on timescales of hours. The X-ray flux in the 2Y10 keV band seen by XMM-Newton was only 0.7% of the flux maximum seen by RXTE. The slope of the X-ray continuum above 5 keV did not vary in any observation, which suggests that the electron temperature of the hottest plasma did not vary significantly at any phase. Through the minimum, the absorption to the stellar source increased by a factor of 5Y10 to N H $ (3Y 4) ; 10 23 cm À2 . These variations were qualitatively consistent with emission from the WWC plasma entering into the dense wind of the massive primary star. During the minimum, X-ray spectra also showed significant excesses in the thermal Fe xxv emission line on the red side, while they showed only a factor of 2 increase in equivalent width of the Fe fluorescence line at 6.4 keV. These features are not fully consistent with the eclipse of the X-ray plasma and may suggest an intrinsic fading of the X-ray emissivity. The drop in the WWC emission revealed the presence of an additional X-ray component that exhibited no variation on timescales of weeks to years. This component may be produced by the collision of high-speed outflows at v $ 1000Y2000 km s À1 from Car with ambient gas within a few thousand AU from the star.

We have made an extensive study of the UV spectrum of η Carinae, and find that we do not directly observe the star and its wind in the UV. Because of dust along our line of sight, the UV light that we observe arises from bound-bound scattering at large impact parameters (e.g., 0.033 ′′ ). We obtain a reasonable fit to the UV spectrum by using only the flux that originates outside 0.033 ′′ . This explains why we can still observe η A in the UV despite the large optical extinction -it is due to the presence of an intrinsic coronagraph in the η Carinae system, 1 Lise-Meitner fellow