The XMM-Newton X-ray observatory took part in the multi-wavelength observing campaign of the massive , evolved star \eta Carinae in 2003 during its recent X-ray minimum .
This paper reports on the results of these observations , mainly from the aspect of spectral change .
Hard X-ray emission from the point source of \eta Carinae was detected even during the minimum .
During the minimum the observed flux above 3 keV was \sim 3 \times 10 ^ { -12 } ergs cm ^ { -2 } s ^ { -1 } , which is about one percent of the flux before the minimum .
Changes in the spectral shape revealed two X-ray emission components in the central point source .
One component is non-variable and has relatively cool plasma of kT \sim 1 keV and moderate absorption , N _ { H } \sim 5 \times 10 ^ { 22 } cm ^ { -2 } .
The plasma is probably located far from the star , possibly produced by the high speed polar wind from \eta Carinae .
The other high temperature component has kT \sim 5 keV and is strongly variable .
This component shows an increase in the apparent column density from 5 \times 10 ^ { 22 } cm ^ { -2 } to 2 \times 10 ^ { 23 } cm ^ { -2 } , probably originating near the heart of the binary system .
These changes in N _ { H } were smaller than expected if the minimum is produced solely by an increase of hydrogen column density .
The X-ray minimum seems to be dominated by a decrease of the apparent emission measure , suggesting that the brightest part of the X-ray emitting region is completely obscured during the minimum in the form of an eclipse .
A “ partial covering ” model might explain the residual emission seen during the minimum .