Maximum strength of the magnetic field in the core of the most massive white dwarfs

Abstract

Massive white dwarfs endowed with ultrastrong magnetic fields have been recently proposed as the progenitors of overluminous type Ia supernovae. In our previous work, we have shown that such stars would become unstable against electron captures if the magnetic field is too strong. Using a more realistic model of dense matter taking into account electron-ion interactions and allowing for ionic mixtures, we estimate the strength of the magnetic field for the onset of electron captures in the core of the most massive white dwarfs. We have considered various compositions and lattice structures. The possibility of pycnonuclear fusion reactions and their impact on the stellar magnetic fields are also discussed. The strongest magnetic fields we find are considerably lower than those previously assumed in putative super-Chandrasekhar white dwarfs.