Binary White Dwarf Systems

Cataclysmic variables, extremely low mass white dwarfs, and white dwarf mergers

White Dwarf Research Summary

Credit: Dr. Mark A.Garlick While most of my research is in type Ia supernovae, I have also been involved in research regarding a variety of other white dwarf binary systems. In particular, I am interested in extremely low mass white dwarfs, cataclysmic variable stars, and other white dwarf merger events.

Extremely Low Mass White Dwarfs

ELM white dwarfs are helium white dwarfs with masses less than around 0.3 solar masses. White dwarfs of this size originating from single star systems would not yet exist given the timescale of stellar evolution for the lowest mass stars, therefore all ELM white dwarfs are in binary systems. Several of these ELM white dwarfs show excess calcium on the surface, suggesting active accretion of material. I compared the spectral energy distributions of 22 ELM white dwarfs and compared them to synthetic spectra to look for excess in infrared flux that would indicate the presence of a debris disk.

Collaborators: M. Kilic, W. Brown, A. Giannias

Cataclysmic Variables

AR Sco is the first known white dwarf pulsar. The system consists of an asynchronously rotating, magnetized white dwarf that interacts with its red-dwarf companion, producing large amplitude variations on the time scales of minutes. Several years of high-time-resolution imaging can precisely constrain the spin-down rate of the white dwarf. I helped determine the spin-down rate by fitting both linear and quadratic functions to the beat-pulse timing data. The precise spin-down rate confirms that the energy released from the spin decay is enough to power the pulsations.

Collaborators: P. Garnavich, C. Littlefield, R. Stiller

Non-SN Ia White Dwarf Mergers

J005311 is a white dwarf merger candidate in the constellation of Casseopeia. Time-resolved spectra show rapid variability in O VI, attributed to clumpiness in the stellar wind. While the variability looks very Wolf-Rayet-like, the velocity of the wind is significantly higher than has been seen in Wolf-Rayets. This object has since been tied to an ancient SN Iax, which is similar to a SN Ia but does not completely destroy the progenitor. I was involved with observing J005311 using the Large Binocular Telescope to obtain high-time-resolution spectra.

Collaborators: P. Garnavich, C. Littlefield, C. A. Thomas

Upcoming Related Work

I am not actively involved in any of this research at the moment, although I do keep up with the field and maintain my collaborations.

Related Publications

Date Title & Authors Links
09/2020 Rapid Variability in the Wind from the White Dwarf Merger Candidate J005311
P. Garnavich, C. Littlefield, R. Pogge, C. M. Wood; RNAAS 4,167 		[ADS] [arXiv]
10/2018 High-time-resolution Photometry of AR Scorpii: Confirmation of the White Dwarf’s Spin-down
R. A. Stiller, C. Littlefield, P. Garnavich, C. M. Wood, et al.; AJ 156,150 		[ADS] [arXiv]

Related Talks & Presentations

Date Location Type
01/13/2021 237th Meeting of the AAS, virtual Contributed iPoster
12/10/2015 Undergraduate Research Day, Hofstra University, Hempstead, NY Contributed poster