Electron-cyclotron maser emission from white dwarf pairs and white dwarf planetary systems

By analogy to Jovian radio emissions powered by the electromagnetic interaction between Jupiter and its moons, we propose that close magnetic-non-magnetic white dwarf pairs and white dwarf planetary systems are detectable radio sources. A simple model is developed to predict the flux densities of radio emission generated by a loss-cone-driven electron-cyclotron maser. The radio emission from these systems has high brightness temperatures, is highly polarized, and varies on a periodic cycle following the orbital rotation. Masers from magnetic-non-magnetic white dwarf pairs, with orbital periods less than or similar to10 min, are expected to be detectable over a wide range of radio frequencies. Terrestrial planets in close orbits about magnetic white dwarfs, with orbital periods less than or similar to30 h, can also produce detectable radio emission, thus providing a means to identify Earth-sized extrasolar planets.