1996NewA....1..245W

<P>We measured the extragalactic 0.7 keV X-ray background by observing the X-ray shadow of a neutral gas cloud in the Magellanic Bridge region. Two ROSAT PSPC observations of total 104 ks were complemented by a detailed H I mapping of the cloud with both the Parkes 64 m telescope and the Australia Telescope Compact Array. From the detected anti-correlation between the observed background intensity and the H I column density of the cloud, we derived the unabsorbed extragalactic background intensity as ∼ 28 keV s^-1 cm^-2 keV^-1 sr^-1 at ∼ 0.7 keV. The 95% confidence lower limit 18 keV s^-1 cm^-2 keV^-1 sr^-1 is greater than the expected point-like source contribution ≲ 14 keV s^-1 cm^-2 keV^-1 sr^-1, constrained by the mean source spectrum together with the total background intensity in the 1-2 keV band. A significant fraction of the 0.7 keV background likely arises in a diffuse hot intergalactic medium of a few million degrees, as has been predicted in hydrodynamic simulations of cosmological structure formation.</P>