Luminosity and cooling suppression in magnetized white dwarfs

TL;DR

This study models how strong magnetic fields in white dwarfs reduce their luminosity and cooling rates, suggesting they can be hidden in observations and evolve differently than non-magnetized counterparts.

Contribution

It provides a detailed analysis of the effects of intense magnetic fields on white dwarf structure, luminosity, and cooling, which was not thoroughly explored before.

Findings

Luminosity decreases by orders of magnitude with increasing magnetic field strength.

Core temperature increases as the magnetic field strength grows.

Cooling rates are significantly suppressed in highly magnetized white dwarfs.

Abstract

We investigate the luminosity and cooling of highly magnetized white dwarfs where cooling occurs by the diffusion of photons. We solve the magnetostatic equilibrium and photon diffusion equations to obtain the temperature and density profiles in the surface layers of these white dwarfs. With increase in field strength, the degenerate core shrinks in volume with a simultaneous increase in the core temperature. For a given white dwarf age and for a fixed interface radius or temperature, the luminosity decreases significantly from $\sim 10^{-6}\, L_{\odot}$ to $10^{-9}\, L_{\odot}$ as the field strength increases from $\sim 10^9$ to $10^{12}\,$G in the surface layers. This is remarkable as it argues that magnetized white dwarfs can remain practically hidden in an observed H--R diagram. We also find that the cooling rates for these highly magnetized white dwarfs are suppressed significantly.