Mass-radius relation of strongly magnetized white dwarfs

TL;DR

This paper investigates how strong magnetic fields influence white dwarf structures, revealing significant mass increases and stability considerations, which could explain over-luminous type-Ia supernovae.

Contribution

It provides a self-consistent analysis of magnetized white dwarf configurations, including effects of magnetic field geometry, Landau quantization, and general relativity, extending previous models.

Findings

Maximum mass of about 1.9 M$_\\odot$ with poloidal fields

Maximum mass over 5 M$_\\odot$ with toroidal fields

Magnetic instabilities grow at Alfven time scales

Abstract

We study the strongly magnetized white dwarf configurations in a self-consistent manner as a progenitor of the over-luminous type-Ia supernovae. We compute static equilibria of white dwarf stars containing a strong magnetic field and present the modification of white dwarf mass-radius relation caused by the magnetic field. From a static equilibrium study, we find that a maximum white dwarf mass of about 1.9 M$_\odot$ may be supported if the interior poloidal field is as strong as approximately $10^{10}$ T. On the other hand if the field is purely toroidal the maximum mass can be more than 5 M$_\odot$. All these modifications are mainly from the presence of Lorenz force. The effects of i) modification of equation of state due to Landau quantization, ii) electrostatic interaction due to ions, iii) general relativistic calculation on the stellar structure and, iv) field geometry are also considered. These strongly magnetised configurations are sensitive to magnetic instabilities where the perturbations grow at the corresponding Alfven time scales.