Discovery of a Nearby Ultra-fast Magnetic White Dwarf Propeller: Common Pathways to Magnetic Cataclysmic Variables
Abstract
The fastest spinning white dwarfs (WDs), which approach break-up speeds, are found in close binary systems. In the two known magnetic WD ``propellers'', AE~Aqr and LAMOST J0240+1952, the magnetic WD spins so rapidly that it ejects the material transferred by its Roche-lobe-filling companion rather than accreting it. We report the discovery of the third such system, 1eRASS J042633.5−250226 (1eRASS J0426/Valeria), at only 265 pc, identified by combining SRG/eROSITA and \textit{Gaia} data via the ``X-ray Main Sequence''. TESS photometry shows AE~Aqr-like flaring and orbital modulation with Porb ≈ 6.62 hr, and ZTF shows month-long high/low state changes. Phase-resolved Palomar/DBSP spectroscopy confirms the orbital period and yields a donor radial velocity of K2 = 202±7 km s−1. High-speed Palomar/CHIMERA photometry detects optical pulsations on three nights with the strongest detection at Pspin = 26.8 sec, though further observations are needed to confirm this as the WD spin. Spectral fitting of the donor in the low state reveals a late K-type star with Tdonor = 4100±150 K. Zeeman splitting in the optical spectrum yields a candidate field strength of BWD = 26 ± 3 MG, meaning the system will evolve into a polar. Like other WD propellers, the system is X-ray faint (LX ≈ 7× 1030 erg s−1), but is not detected in the radio, and a spin period is not detected in X-rays by SRG/eROSITA. The proximity of this system and evolutionary model constraints on the timeframe of the propeller phase yield a birth rate density of ∼8×10−16 pc−3 yr−1, which agrees with that of magnetic CVs, suggesting that a substantial fraction of magnetic CVs pass through a propeller phase.
Related
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BibTeX
@misc{rodriguez2026discovery,
title = {{Discovery of a Nearby Ultra-fast Magnetic White Dwarf Propeller: Common Pathways to Magnetic Cataclysmic Variables}},
author = {Antonio C. Rodriguez and Kareem El-Badry and R. Michael Rich and Kevin N. Ortiz Ceballos and Ingrid Pelisoli and Casey J. Law and Kaya Mori and Boris Gaensicke and Edo Berger and Liam Connor and Ilkham Galiullin and Ilaria Caiazzo and Matthew Graham and Samuel Whitebook},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10689},
eprint = {2610.10689},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10689},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Discovery of a Nearby Ultra-fast Magnetic White Dwarf Propeller: Common Pathways to Magnetic Cataclysmic Variables
AU - Antonio C. Rodriguez
AU - Kareem El-Badry
AU - R. Michael Rich
AU - Kevin N. Ortiz Ceballos
AU - Ingrid Pelisoli
AU - Casey J. Law
AU - Kaya Mori
AU - Boris Gaensicke
AU - Edo Berger
AU - Liam Connor
AU - Ilkham Galiullin
AU - Ilaria Caiazzo
AU - Matthew Graham
AU - Samuel Whitebook
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.10689
UR - https://arxiv.org/abs/2610.10689
AB - The fastest spinning white dwarfs (WDs), which approach break-up speeds, are found in close binary systems. In the two known magnetic WD ``propellers'', AE~Aqr and LAMOST J0240+1952, the magnetic WD spins so rapidly that it ejects the material transferred by its Roche-lobe-filling companion rather than accreting it. We report the discovery of the third such system, 1eRASS J042633.5−250226 (1eRASS J0426/Valeria), at only 265 pc, identified by combining SRG/eROSITA and \textit{Gaia} data via the ``X-ray Main Sequence''. TESS photometry shows AE~Aqr-like flaring and orbital modulation with P_orb ≈ 6.62 hr, and ZTF shows month-long high/low state changes. Phase-resolved Palomar/DBSP spectroscopy confirms the orbital period and yields a donor radial velocity of K_2 = 202±7 km s^−1. High-speed Palomar/CHIMERA photometry detects optical pulsations on three nights with the strongest detection at P_spin = 26.8 sec, though further observations are needed to confirm this as the WD spin. Spectral fitting of the donor in the low state reveals a late K-type star with T_donor = 4100±150 K. Zeeman splitting in the optical spectrum yields a candidate field strength of B_WD = 26 ± 3 MG, meaning the system will evolve into a polar. Like other WD propellers, the system is X-ray faint (L_X ≈ 7× 10^30 erg s^−1), but is not detected in the radio, and a spin period is not detected in X-rays by SRG/eROSITA. The proximity of this system and evolutionary model constraints on the timeframe of the propeller phase yield a birth rate density of ∼8×10^−16 pc^−3 yr^−1, which agrees with that of magnetic CVs, suggesting that a substantial fraction of magnetic CVs pass through a propeller phase.
ER -