Found: a rapidly spinning white dwarf in LAMOST J024048.51+195226.9
arXiv:2108.11396 · doi:10.1093/mnrasl/slab116
Abstract
We present optical photometry of the cataclysmic variable LAMOST J024048.51+195226.9 taken with the high-speed, five-band CCD camera HiPERCAM on the 10.4 m Gran Telescopio Canarias (GTC). We detect pulsations originating from the spin of its white dwarf, finding a spin period of 24.9328(38)s. The pulse amplitude is of the order of 0.2% in the g-band, below the detection limits of previous searches. This detection establishes LAMOST J024048.51+195226.9 as only the second white dwarf magnetic propeller system, a twin of its long-known predecessor, AE Aquarii. At 24.93s, the white dwarf in LAMOST J024048.51+195226.9 has the shortest known spin period of any cataclysmic variable star. The white dwarf must have a mass of at least 0.7MSun to sustain so short a period. The observed faintest u-band magnitude sets an upper limit on the white dwarf's temperature of ~25000K. The pulsation amplitudes measured in the five HiPERCAM filters are consistent with an accretion spot of ~30000K covering ~2% of the white dwarf's visible area, although spots that are hot and smaller, or cooler and larger cannot be ruled out.
5 pages, 5 figures. Updated to match the version published in MNRAS Letters
References in corpus (14)
- The Catalina Surveys Periodic Variable Star Catalog
- On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
- The origin and evolution of magnetic white dwarfs in close binary stars
- white dwarfs within 40 pc II: the volume-limited northern hemisphere sample
- Testing the white dwarf mass-radius relationship with eclipsing binaries
- HiPERCAM: a quintuple-beam, high-speed optical imager on the 10.4-m Gran Telescopio Canarias
- Roche tomography of cataclysmic variables -- III. Starspots on AE Aqr
- V1460 Her: A fast spinning white dwarf accreting from an evolved donor star
- CTCV J2056-3014: An X-ray-faint Intermediate Polar Harboring An Extremely Fast-spinning White Dwarf
- The White Dwarf in AE Aqr Brakes Harder
- Follow-up Studies of Five Cataclysmic Variable Candidates Discovered by LAMOST
- Radio and optical observations of the possible AE Aqr twin, LAMOST J024048.51+195226.9
- HD 49798: Its History of Binary Interaction and Future Evolution
- Confirmation of a Second Propeller: A High-Inclination Twin of AE~Aquarii