Catalog of Magnetic White Dwarfs with Hydrogen Dominated Atmospheres

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 (WDs) 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 nonmagnetic WDs, the literature already shows that the magnetic ones have on average higher mass than the nonmagnetic. 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.

Anisotropic pressure effect on strongly magnetized white dwarfs using quasi-local equation of state

“…The effects of general relativity in the maximum mass of the star are small, around 2% [50][51][52][53], so we do not expect these effects to change the stability state of the star. May be the reason of the instability is using the assumption of spherical symmetry, where the results shows that the star is deformed by its internal magnetic field.…”

A Quantum-mechanical Treatment of Electron Broadening in Strong Magnetic Fields

“…When trying to estimate the magnetic fields in stars, measured spectra are often compared against "spaghetti plots" that show the evolution of the atomic transitions with magnetic field strength (e.g., Amorim et al 2023). The evolution of these transitions generally include all of the abovementioned regimes of magnetic fields: weak field, Paschen-Back, and Landau.…”