A Search for Variability in C-rich DQ White Dwarfs

Document Type


Degree Name

Master of Science (MS)


Physics and Astronomy

Date of Award

Spring 2018


Hot DQ white dwarfs are a rare class of white dwarfs that have atmospheres dominated by carbon with little to no hydrogen or helium. Recently it has been found that the majority of these stars are photometrically variable, likely due to rapid rotation with star spots. The cool progeny of the hot DQs are expected to also be rapidly rotating as no strong braking mechanisms are believed to be present. My collaborator and I present the time-series photometry of multiple warm and cool C-rich DQ white dwarfs as part of an ongoing search for variability in hot DQ white dwarfs and their progeny. This program was an attempt to confirm rotation by comparing the distribution of rotation rates of cool second-sequence DQs to that of their suspected hot DQ progenitors. We failed to find rapid rotation in cool DQs but did find tantalizing evidence of slow rotation in several stars, implying either a previously unrecognized braking mechanism, a loss of the magnetic spot, or that the variability not due to rapid rotation. We hypothesized that stellar winds may be removing angular momentum from these stars.


Kurtis Williams

Subject Categories

Physical Sciences and Mathematics | Physics