Institute of Astronomy

The tug of white dwarf planets or something else entirely? The cautionary tale of GD 66.

SpeakerTalk DateTalk Series
JJ Hermes29 July 2014Across HR 2014 Talks


A subset of pulsating white dwarfs serve as exceptionally stable optical clocks, which can be monitored for reflex orbital motion caused by planetary companions. The hot subdwarf B star CS 1246 demonstrates that the pulse-timing technique is a reliable way to detect unseen companions to stellar remnants, which were confirmed by follow-up, radial-velocity observations. Periodic timing variations of the pulsating white dwarf GD 66 garnered attention as evidence of a planetary companion. I will present complications to this planetary hypothesis, and show that this white dwarf offers a cautionary tales in the quest for claiming the detection of planets around evolved stars. I will also discuss the useful limits we can now place on a lack of close-in planets to evolved extrasolar systems: After more than a decade of monitoring a sample of pulsating white dwarfs from the McDonald Observatory, we can now exclude Jupiter-mass planets out to 10 AU for at least six stars in this sample.