We present the discovery of the shortest-period , non-interacting , white dwarf-brown dwarf post-common-envelope binary known .
The K2 light curve shows the system , EPIC 21223532 has a period of 68.2 min and is not eclipsing , but does show a large reflection effect due to the irradiation of the brown dwarf by the white dwarf primary .
Spectra show hydrogen , magnesium and calcium emission features from the brown dwarf ’ s irradiated hemisphere , and the mass indicates the spectral type is likely to be L3 .
Despite having a period substantially lower than the cataclysmic variable period minimum , this system is likely a pre-cataclysmic binary , recently emerged from the common-envelope .
These systems are rare , but provide limits on the lowest mass object that can survive common envelope evolution , and information about the evolution of white dwarf progenitors , and post-common envelope evolution .