Probing the Deep Interiors of Accreting White Dwarfs through Studies of their Non-Radial Oscillations

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AST-0205956PI BildstenWhite dwarfs (WDs) are the most common collapsed objects produced as end points of stellar evolution. Their astrophysical behavior depends on their interior composition affecting both the rate at which these objects cool from birth and how they explode as supernovae if heated to high temperatures later in life by accreting material from a nearby companion star. Deep interior compositions may be probed by studying the properties of certain volumetric oscillations having periods of 100-1000 seconds. This project is a theoretical investigation of these non-radial oscillations and it addresses certain frontier questions. The most abundant atomic nucleus in the WD interior after carbon and oxygen is an isotope of neon that tends to sink towards the WD center. Interpreting observations of these objects requires the theoretical modeling of this project to understand how the oscillations and the cooling times are affected by the neon sedimentation and consequent composition gradient. A second aspect of this project follows from the recent discovery of a pulsating WD in a mass transferring binary system. This finding has opened up a new field in astrophysics. Another set of theoretical calculations are required for such objects in this environment in order to convert observed pulsation periods that are comparable to the rotation periods of these stars into measurements of WD properties such as mass and the rotation rate.***