Photometric variability of White Dwarfs with Kepler and K2
Stellar, Exoplanet and Galactic Science from Massive, High-precision Variability Surveys
Mr I. Braker
University of Leicester
Dr M.R. Burleigh (University of Leicester), Prof M.A. Barstow (University of Leicester), Dr K.A. Lawrie (University of Leicester), Prof J.B. Holberg (University of Arizona)
It has long been assumed that the vast majority of white dwarfs are photometrically stable, at the level of at least a few mmags. Alongside the well known non-radial pulsators, we have shown that 30−40% of magnetic White Dwarfs vary on their rotation periods due to star spots or magnetic dichroism (Brinkworth et al. 2013, Lawrie et al. 2015), but these constitute no more than 10% of the overall population. Significantly, however, the exquisite precision of Kepler photometry has shown that as many as 50% of all white dwarfs may be intrinsically variable (Maoz et al 2015) but these, mainly non-magnetic, white dwarfs cannot all be explained by such mechanisms. Alternatively, this behaviour may be due to the accretion of metal rich material or the presence of an ultra-low mass companion. Whilst only a handful of white dwarfs (approximately 16) were observed in the original Kepler field, the Kepler 2 (K2) mission is anticipated to observe several hundred during its operational lifetime. The K2 mission will hence allow us to extend this survey to search for periodic and transit like features in a larger sample of white dwarfs. We discuss our preliminary results from our ongoing analysis of the white dwarfs in the K2 fields and the potential implications.
16:30 - 18:00