Precision Astrometry of the Exoplanet Host Candidate GD 66
  The potential existence of a giant planet orbiting within a few AU of a stellar remnant has profound implications for both the survival and possible regeneration of planets during post-main sequence stellar evolution. This paper reports Hubble Space Telescope Fine Guidance Sensor and U.S. Naval Observatory relative astrometry of GD 66, a white dwarf thought to harbor a giant planet between 2 and 3 AU based on stellar pulsation arrival times. Combined with existing infrared data, the precision measurements here rule out all stellar-mass and brown dwarf companions, implying that only a planet remains plausible, if orbital motion is indeed the cause of the variations in pulsation timing. 
J. Farihi, J. P. Subasavage, E. P. Nelan, H. C. Harris, C. C. Dahn, J.   Nordhaus, D. S. Spiegel
astro-ph.EP astro-ph.SR