The Ultra Compact sdB+WD binary CD -30 11223

We have recently discovered that CD 30 11223 is a binary composed of a whitedwarf orbiting a subdwarf of B spectral type in only 1.2 hours. This is by farthe shortest orbital period of any sdB+WD binary. The orbital separation of only0.6 solar radii implies that the subdwarf is very close to fill its Rochelobe,making this system an optimal candidate for observations at Xray energies.Xray observations can give information on properties of the white dwarfunaccessible in other bands, which are particularly interesting given thepossibility that this close binary be the progenitor of a SN Ia via thesocalled subChandrasekhar doubledetonation scenario. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]