Spectrophotometric analysis of magnetic white dwarf II: Helium-rich compositions

TL;DR

This paper analyzes helium-rich magnetic white dwarfs using spectroscopic data and advanced models to determine their physical properties, revealing diverse magnetic geometries and a group of highly magnetic featureless white dwarfs.

Contribution

It introduces improved modeling of magnetic effects on helium-rich white dwarf spectra and provides detailed physical parameters for a sample of such stars.

Findings

Successful spectral reproduction for 8 objects with offset dipole models

Indications of complex magnetic geometries in some white dwarfs

Identification of highly magnetic, featureless white dwarfs

Abstract

We present an analysis of all single white dwarf stars known to exhibit spectroscopic signatures of neutral helium line splitting due to the presence of a strong magnetic field. Using state-of-the-art models taking into account the effects of magnetic fields on the synthetic spectra, we determine effective temperatures, surface gravities and masses for the stars in our sample. Our analysis uses data from the second and third Gaia (early) data release, photometric data from diverse surveys such as the Sloan Digital Sky Survey and Pan-STARRS, and archived spectroscopic data. We are able to successfully reproduce the spectra of 8 objects using an offset dipole geometry while several others seem to require either a more complexe geometry or a different chemical composition. We also highlight a group of hot featureless white dwarfs that are most probably highly magnetic objects whose spectra are completely smeared due to the field strength distribution across the surface.