Cooling of neutron stars with strong toroidal magnetic fields

Abstract

We present models of temperature distribution in the crust of a neutron star in the presence of a strong toroidal component superposed to the poloidal component of the magnetic field. The presence of such a toroidal field hinders heat flow toward the surface in a large part of the crust. As a result, the neutron star surface presents two warm regions surrounded by extended cold regions and has a thermal luminosity much lower than in the case the magnetic field is purely poloidal. We apply these models to calculate the thermal evolution of such neutron stars and show that the lowered photon luminosity naturally extends their life-time as detectable thermal X-ray sources. Keywords

Topological currents in neutron stars: kicks, precession, toroidal fields, and magnetic helicity

“…Strong observational evidence, see [63] and references therein, supporting the presence of the toroidal component unambiguously suggests that the magnetic helicity H must be non-zero in neutron stars. The P-odd quality of the magnetic helicity may be strong, indirect evidence supporting our claim that P-odd topological currents have been induced at some moment in the star's life.…”

“…References [29,28,30,61,62] argue that toroidal and poloidal fields of similar magnitudes must be necessary to stave off hydrodynamic instabilities-the toroidal field suppresses poloidal instabilities and vice versa. Much has been done to find the observational consequences of a toroidal field, for example [63].…”

Stellar Superfluids

“…For example, a > ∼ 10 14 G toroidal field within the crust can act as an efficient insulator, rendering most of the star's surface very cold, but having two hot spots on the symmetry axis of the torus [129,130]. This results in peculiar cooling trajectories [131]. The second effect of a magnetic field is that a slowly decaying field can act as a source of energy (i.e., the "H" term in Eq.…”