Magnetic White Dwarfs from DESI

Abstract A significant fraction of white dwarfs, the degenerate remnants of low- and intermediate-mass stars, host strong magnetic fields; yet the origin and evolution of these magnetic fields remain poorly understood. Building a large, statistically robust sample of these magnetic white dwarfs (MWDs) is crucial for testing competing theories of field generation. We used the white dwarf candidates catalog from Gaia DR3 to select objects with spectra from the first data release of the Dark Energy Spectroscopic Instrument (DESI) survey. We identified candidate MWDs through visual inspection of their spectra, searching for the characteristic Zeeman splitting of absorption lines. After cross-matching with the literature, we present the discovery of 137 new MWDs. Follow-up analysis and atmospheric modeling were used to determine magnetic field strengths ranging from approximately 1 to nearly 500 MG. Our findings demonstrate the exceptional capability of large-scale spectroscopic surveys, such as DESI, to uncover rare stellar populations and advance our understanding of compact-object astrophysics.