Magnetic white dwarf RXJ0528+2838 drives 1000-year bow shock without accretion disk

The Isaac Newton Telescope first flagged the arc-shaped nebula; MUSE integral-field spectroscopy then mapped its kinematics and composition, confirming the white dwarf binary as the source. No disk signatures appear in the spectra, yet the bow shock implies continuous mass ejection at rates sufficient to maintain the structure for at least a millennium. The system’s known strong magnetic field is the only remaining candidate mechanism capable of channeling companion material directly onto the white dwarf poles while still powering an extended outflow.

Standard theory requires an accretion disk to launch and collimate outflows in cataclysmic variables; its absence here forces reconsideration of magnetic propeller or reconnection-driven ejection scenarios previously dismissed for low-accretion states. Related systems such as AE Aquarii and AR Scorpii show pulsed radio and X-ray emission tied to rapid rotation and strong fields, yet lack comparable large-scale nebulae, highlighting that RXJ0528+2838 occupies a previously unrecognized parameter space.

If magnetic channeling alone sustains the outflow, similar isolated magnetic white dwarfs should exhibit faint bow shocks detectable in wide-field H-alpha surveys. Targeted X-ray and radio monitoring over the next two years can test whether the inferred mass-loss rate exceeds 10^-10 solar masses per year, a threshold that would require revision of angular-momentum-loss prescriptions used in binary population synthesis.

The finding also bears on Type Ia supernova progenitor channels: sustained outflows without disks could alter the white dwarf’s net mass-growth rate, shifting the parameter space where single-degenerate systems reach the Chandrasekhar limit.