Evolution of spin and orbital periods in isolated white dwarfs and related binary systems

Brinkworth, Carolyn (2005) Evolution of spin and orbital periods in isolated white dwarfs and related binary systems. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Variability in isolated white dwarfs and associated binary systems can reveal a large amount of information about the source. We have used photometric variability to derive the spin periods of seven magnetic white dwarfs, and in the process we have discovered variability in ~55% of our sample. We believe that in at least two of our sources we have discovered the first star spots ever to be detected on the surfaces of white dwarfs. We also investigate the changing period of the eclipsing pre-cataclysmic variable NN Ser by measuring the timings of the system’s mid-eclipses using the high-speed CCD camera, ULTRACAM. We find that the period is shortening at an average rate of Ṗ; = (9.057 ± 0.005) x 10^-12, consistent with standard models of orbital period change derived for much more massive secondary stars, and two orders of magnitude higher than the current theoretical prediction. We also discuss other potential mechanisms for this observed period change.

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