GD 552: a cataclysmic variable with a brown dwarf companion?
  GD 552 is a high proper motion star with the strong, double-peaked emission lines characteristic of the dwarf nova class of cataclysmic variable star, and yet no outburst has been detected during the past 12 years of monitoring. We present spectroscopy taken with the aim of detecting emission from the mass donor in this system. We fail to do so at a level which allows us to rule out the presence of a near-main-sequence star donor. Given GD 552's orbital period of 103 minutes, this suggests that it is either a system that has evolved through the ~80-minute orbital period minimum of cataclysmic variable stars and now has a brown dwarf mass donor, or that has formed with a brown dwarf donor in the first place. This model explains the low observed orbital velocity of the white dwarf and GD 552's low luminosity. It is also consistent with the absence of outbursts from the system. 
E. Unda-Sanzana, T. R. Marsh, B. T. Gansicke, P. F. L. Maxted, L.   Morales-Rueda, V. S. Dhillon, T. D. Thoroughgood, E. Tre...