€Four models exist for
these systems
a)Intermediate Polar Motch et al (1996)
Norton et al (2002)
b)Double Degenerate Polar Cropper et al (1998)
c)Double Degenerate Algol Marsh & Steeghs (2002)
Ramsay et al (2002)
d)Electric Star Wu et al (2002)
e)
€Of these models, three
involve magnetic fields
€Neutron star models are
ruled out because of the
absence of a hard tail of X-ray emission; also
they
need
to be extremely close
(too close for the observed level of reddening)