T Marsh

Tom Marsh

University of Warwick

Dynamical Effects in Timing Tests of Planetary Companions around White Dwarf Binaries


There have been a number of claims of one or more planetary-mass companions to eclipsing white dwarf close binaries, revealed through variations in their eclipse times. These are sensitive to low mass planets, especially in long period orbits, and are interesting in terms of planetary survival through the late stages of host star evolution and possible planet formation from stellar ejecta. However, there is doubt over the reality of the planets around these systems as there are mechanisms for inducing timing variations in binaries that do not require planets. Moreover, several proposed multiple planet solutions have been shown to be wrong in the light of new data or dynamically unstable. In this talk I will look at the issue of dynamical stability. In particular I will show that dynamical effects have to be included from the very start when fitting the orbits. This invalidates much of the existing literature on dynamical stability in these binaries since it is standard to fit the orbits assuming Keplerian orbits. I show that in the system NN Ser, which appears to be tracking planetary companion predictions well, there are dynamically stable orbits that fit the data.

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