Catalog of magnetic white dwarfs with hydrogen dominated atmospheres

TL;DR

This study provides a comprehensive catalog of 804 hydrogen-rich white dwarfs with measured magnetic fields, revealing correlations between magnetic strength, mass, and temperature, and suggesting magnetic field amplification during cooling.

Contribution

It presents the largest dataset of magnetic field measurements in hydrogen-rich white dwarfs, using spectral fitting to analyze their magnetic properties.

Findings

Magnetic white dwarfs tend to have higher masses than non-magnetic ones.

Magnetic fields are more prevalent in cooler white dwarfs.

Higher magnetic fields correlate with higher masses and lower temperatures, indicating ongoing crystallization.

Abstract

White dwarfs are excellent research laboratories as they reach temperatures, pressures, and magnetic fields that are unattainable on Earth. To better understand how these three physical parameters interact with each other and with other stellar features, we determined the magnetic field strength for a total of 804 hydrogen-rich white dwarfs of which 287 are not in the literature. We fitted the spectra observed with the Sloan Digital Sky Survey using atmospheric models that consider the Zeeman effect due to the magnetic field at each point in the stellar disk. Comparing magnetic and non-magnetic WDs, the literature already shows that the magnetic ones have on average higher mass than the non-magnetic. In addition to that, magnetic fields are more common in cooler WDs than in hotter WDs. In consonance, we found that those with higher magnetic field strengths tend to have higher masses, and lower temperatures, for which models indicate the crystallization process has already started. This reinforces the hypothesis that the field is being generated and/or amplified in the cooling process of the white dwarf. Our sample constitutes the largest number of white dwarfs with determined magnetic fields to date.