Evolutionary state of nearly pure-cyclotron-emission white-dwarf binaries

Determine whether white-dwarf binaries exhibiting almost pure cyclotron emission with little or no Balmer or helium emission are detached systems before mass transfer or systems that have passed the onset of mass transfer.

Background

The paper discusses magnetic white-dwarf binaries with weak or nearly absent conventional emission lines and very low accretion rates. Their evolutionary state is unsettled: they may be detached systems preceding mass transfer or systems that have already begun mass transfer but are presently in a very low-accretion state.

References

The general consensus is that the majority of white dwarf binaries emitting almost pure cyclotron emission, with little or no sign of Balmer or He emission lines, are in a detached state, with some ongoing discussion around whether they are prior to or past the onset of mass transfer \citep{Vogel2007, Schreiber2021}.

— The DESI Data Release 1 white dwarf catalogue  (2609.04314 - Swan et al., 3 Sep 2026) in Section 5.8.3, Low-accretion-rate polars