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 postmain-sequence stellar evolution. This paper reports Hubble Space Telescope Fine Guidance Sensor and US Naval Observatory relative astrometry of GD 66, a white dwarf thought to harbour 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.