Institute of Astronomy

Planets around Post Common-Envelope Binaries

SpeakerTalk DateTalk Series
Tom Marsh29 July 2014Across HR 2014 Talks


Binary stars with one or more white dwarf or subdwarf components can make good timing sources through eclipses and pulsations. In the best cases, times can be established to better than 0.1 seconds precision, making them sensitive to perturbations from Neptune-like companions on circumbinary orbits. The best current examples are survivors of the ""common envelope"" phase during which both stars orbited within a single envelope formed from the evolved objects which severely constrains the planetary orbits prior to the common envelope, and may in some cases require the planets to form from the envelope itself. In turn, if the existence of the planets can be established beyond all doubt, these systems may offer provide a new handle upon the common envelope phase itself. I will review the observational evidence for planetary companions to evolved binary stars, and discuss the dynamical stability of the systems which appear to have more than one companion. I will show results from a survey of a large number of such systems, including first results on double white dwarf binaries in which interaction within the binary is expected to be negligible.