€All of the variability in Polars occurs at a single period: the orbital period
–radial velocity curves of the secondary
–X-ray light curves from the primary
–polarisation variations
Þthe white dwarf/red dwarf are locked into the same
orientation: synchronised rotation
€The mechanism for synchronisation is the dissipation due to the magnetic field of the
primary being dragged through the secondary
€As relative spin rate of primary decreases, locking can occur due to the dipole-dipole
magnetostatic interaction between primary and (weaker) secondary magnetic
field
€Some Polars not quite in synchronism; in these systems it typically takes 5–50 days for
white dwarf orientation to repeat itself
€Very useful systems to study the effect of orientation of magnetic field on the accretion
process