Limits from the Ongoing Search for Planets Around White Dwarf Stars Using Pulsation Timings

Evidence from searches of stars in our galaxy for exoplanet companions suggests that most lower main sequence stars likely have one or more planets; the vast majority of these planet-hosting stars will evolve into white dwarf stars. Some planets may survive this process and new ones may form in a sort of second generation from the cast-off material. If we combine this argument with evidence of a substantial population of metal polluted white dwarf stars, we may plausibly expect that planets may be common around white dwarf stars. Empirically, however, little is known about the presence of planets, new or old around white dwarf stars. Our search is small (similar to 15 white dwarf stars), but sensitive. Using pulsation arrival times we reach a large search volume around each star: we are sensitive to 1M(Jupiter) planets at distances ranging from 1 - 100AU. In this context, our tightening constraints from pulsation timings become increasingly important to the broader study of planet formation, dynamical evolution, and ultimate survival.