We present limits on planetary companions to pulsating white dwarf stars .
A subset of these stars exhibit extreme stability in the period and phase of some of their pulsation modes ; a planet can be detected around such a star by searching for periodic variations in the arrival time of these pulsations .
We present limits on companions greater than a few Jupiter masses around a sample of 15 white dwarf stars as part of an on-going survey .
One star shows a variation in arrival time consistent with a 2 \mathrm { M _ { J } } planet in a 4.5 year orbit .
We discuss other possible explanations for the observed signal and conclude that a planet is the most plausible explanation based on the data available .