Continuous Gravitational Waves from Magnetized White Dwarfs: Quantifying the Detection Plausibility by LISA

Abstract White dwarfs (WDs) are frequently observed to have strong magnetic fields up to 10 9 G and expected to have a possible internal field as high as ∼10 14 G. High internal fields can significantly deform a WD’s equilibrium structure, generating a quadrupole moment. If the rotation axis is misaligned with the magnetic axis, the deformation can lead to the emission of continuous gravitational waves (CGWs). We examine the potential for detecting CGWs from magnetized WDs with future space-based detectors such as LISA, ALIA, DECIGO, Deci-Hz, the Big Bang Observer, and TianQin. We model the field-induced deformation and compute the resulting GW strain, incorporating amplitude decay due to angular momentum loss from electromagnetic and gravitational radiation. This sets a timescale for detection—an “active timescale” of 10 5 −10 6 yr, requiring observation while the object remains sufficiently young. Our results suggest that LISA could detect a few dozen highly magnetized WDs across the Galaxy during its mission. As a specific case, we investigate ZTF J1901+1458—a compact, massive, fast-rotating, and strongly magnetized WD with spin period ∼416 s and inferred surface field ∼10 9 G. We find that this object would be detectable by LISA with 4 yr of continuous data. This highlights the potential of CGW observations to probe magnetic field structure in WDs and their role in Type Ia supernova progenitors.