A Search for Rapid Rotation in Massive White Dwarf Stars

About 95% of stars in the sky, including the Sun, will end their lives as white dwarfs (WDs), and a majority of these being in binary systems. Double degenerate WDs are the result of the death of both stars in such a system. Depending on the orbital separation, many of these binaries may merge to form a single, massive, rapidly-rotating white dwarf. However, a rapidly rotating, massive WDs could also be remnant of an isolated massive Sun-like star (~4-8 M☉). We can differentiate between these two potential origins of rapidly-rotating massive WDs by determining the distribution of WD rotation periods. Like the Sun, a WD can have starspots that reduce the luminosity of the star when they are in view. Observing these fluctuations in brightness therefore permit determination of the rotation period of a white dwarf. The goal of this project is to increase the number of massive WDs with measured rotation periods by performing time series photometry. Our early observations of three massive WDs has found strong evidence that suggests at least one of them, LAMOST J132743.78+545725.7, is rapidly rotating with a period of 2.170 ± 0.006 hours. Further observations of yet more massive WDs are underway.