Asteroseismology of the Pulsating White Dwarf Stars in the Cataclysmic Variables GW Lib and V386 Ser




Afreen, Fizza

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White dwarf stars (WDs) are the final stage of evolution for approximately 98 % of all stars in the universe in which they are cooling. As WDs cool, they cross instability strips where they are observed to pulsate. WDs are found both in isolation and in binary systems. Cataclysmic Variables (CVs) are interacting binary systems in which the WD accretes matter from a companion star, resulting in an accretion disk around the WD. To date, there are 18 CVs with pulsating WDs. Pulsations were first detected in the WDs in the CVs GW Lib and V386 Ser in 1997 and 2004, respectively, making these the most well-studied systems. I used the published pulsation periods of these WDs to determine their independent modes to probe the internal structure of these stars through asteroseismology. I compared these observed modes to theoretical modes calculated using the White Dwarf Evolution Code (WDEC). I used external mass determinations to guide my searches for the most likely structure of these two stars. My study provides insights on the masses of hydrogen and helium for the WDs in GW Lib and V386 Ser, showing that they are most likely thin. As of the publication of this thesis, our study is one of the first attempts at asteroseismology of WDs in CVs.



White dwarf stars., Cataclysmic variables., Asteroseismology.