GLEAM-X J16279.5-523504.3 as a White Dwarf Pulsar

Abstract: The low frequency radio source GLEAM-X J162759.5$-$523504.3 emits pulsed coherent polarized emission like that of radio pulsars. Yet its period of 18.18 min (1091 s) is hundreds of times longer than those of confirmed radio pulsars, and if it is a neutron star its mean radiated power exceeds the upper limit on its spin-down power by more than an order of magnitude. This may be explained if it is a white dwarf pulsar, with a moment of inertia several orders of magnitude greater than those of neutron stars. The Lorentz factor of the emitting charge bunches may be bounded from below by the widths of the temporal substructure of their radiation. If the emission is curvature radiation, the radius of curvature may be estimated from the Lorentz factor and the frequencies of emission; it is consistent with a white dwarf's inner magnetosphere but not a neutron star's.