Searching for magnetic white dwarfs in LAMOST DR10

¹ Space Physics and Astronomy research unit, PO Box 3000, 90014 University of Oulu, Finland
² Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
³ Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
⁴ Department of Physics, PO Box 64, 00014 University of Helsinki, Helsinki, Finland

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 2 September 2025
Accepted: 8 March 2026

Abstract

Aims. Magnetic white dwarfs (MWDs) are key to understanding the origin and evolution of magnetic fields in compact stars. While large spectroscopic surveys such as SDSS have greatly expanded the known sample, the potential of LAMOST has not yet been fully explored. Our aim is to identify and characterize isolated MWDs in the LAMOST data release ten (DR10).

Methods. We crossmatched LAMOST DR10 spectra with white dwarf candidates from Gaia early data release three (EDR3) and with recent SDSS-based catalogs of MWDs. Zeeman splitting in Balmer and helium absorption lines was used as the primary diagnostic to identify magnetic fields and to estimate their strengths. Reference objects from the SDSS catalogs were used to test the detectability of MWDs in LAMOST low-resolution spectra.

Results. We identified 63 isolated MWDs in LAMOST DR10, 32 of which are new discoveries. Surface magnetic field strengths were measured from Zeeman splitting, covering a range from a few megagauss up to several tens. For previously known SDSS MWDs, our LAMOST-based field measurements mostly show agreement with published values.

Conclusions. This work demonstrates the capability of LAMOST low-resolution spectroscopy to identify and characterize isolated MWDs. The newly discovered objects expand the known population and provide valuable targets for future high-resolution spectroscopic and polarimetric follow-up studies. Our results highlight the potential of combining LAMOST with Gaia and other large surveys to build a more complete census of MWDs.