  XMM-Newton observations of the polar SDSSJ155331.12+551614.5 reveal that all
the X-ray flux emerges at energies less than 2 keV. The best fit to the
spectrum is with a thermal plasma with kT=0.8 keV plus a 20-90 ev black body,
yielding a thermal X-ray luminosity of 8-9.5E28 ergs/s. The low temperature and
X-ray luminosity, together with the lack of variation of the X-ray flux during
the observations, are all consistent with an extremely low accretion rate that
puts the system in the bombardment regime of accretion, rather than accretion
involving a standoff shock. It is likely that the observed X-rays originate
from the M dwarf secondary star, thus providing a base activity level for late
main sequence stars in close binaries. SDSSJ132411.57+032050.5 is detected by
XMM-Newton at the faint EPIC pn count rate of 0.0012 c/s, giving an upper limit
to the X-ray luminosity of 7E28 ergs/s for a distance of 300 pc, which is also
consistent with the above scenario.
