AM Her variables - synchronised magnetic cataclysmic variables (CVs) -
exhibit a different period distribution from other CVs across the period gap. We
show that non-AM Her systems may infiltrate the longer-period end of the period gap
if they are metal-deficient, but that the position and width of the gap in orbital
period is otherwise insensitive to other binary parameters (excepting the
normalisation of the braking rate). In AM Her binaries, magnetic braking is reduced
as the wind from the secondary star may be trapped within the magnetosphere of the
white dwarf primary. This reduced braking fills the period gap from its short-period
end as the dipole magnetic moment of the white dwarf increases. The consistency of
these models with the observed distribution of CVs, both AM Her and non-AM Her type,
provides compelling evidence supporting magnetic braking as the agent of angular
momentum loss among long-period CVs, and its disruption as the explanation of the
2-3 hour period gap among nonmagnetic CVs.
Thursday, May 2 at 4:00 p.m.
Seminars are held in Room 23 of the Dearborn Observatory
Refreshments will be served at 3:35
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