The Effect of the Gravitational Mass on the Electromagnetic Radiation from an Oblique, Relativistically Rotating Dipole (Neutron Star)

TL;DR

This study investigates how the gravitational mass of a neutron star affects its electromagnetic radiation, revealing significant suppression of radiation energy with increasing mass, especially at low angular momentum, and highlighting the retention of rotational energy.

Contribution

It extends existing models by incorporating gravitational mass effects into the electromagnetic radiation from obliquely rotating neutron stars, showing mass-dependent suppression of radiation.

Findings

Mass significantly suppresses electromagnetic radiation at low angular momentum.

Radiation energy is proportional to the square of the sine of the inclination angle.

High angular momentum suppresses radiation regardless of mass effects.

Abstract

Relying on the magnetic dipole model of the pulsar, we use the extension of the work of Haxton-Ruffini [31] for single charges by DePaolis-Ingrosso-Qadir [32] for an obliquely rotating magnetic dipole, to incorporate the effect of the gravitational mass. So, by using the numerical and analytical solutions of the differential equation for the radiation, we construct the energy spectra for different masses of the dipole-NS. These spectra show that, in relatively low angular momentum l, the effect of the gravitational mass is very significant in suppressing the relativistic enhancement factor, which had been found [27, 28, 32], by two to three orders of magnitude, as the mass changes from 0.5 solar mass to 3 solar masses. It is an indication that most of the angular momentum of the NS is retained as rotational kinetic energy instead of being radiated as an electromagnetic energy. Also, the suppressing in radiation energy is more or less independent of the angular momentum, and the high rotational velocity. We also found that electromagnetic energy is proportional to square of sin(inclination angle the obliquity) which is similar to the classical behavior. However, in the very high angular momentum, the whole radiation suppresses and the effect of mass is neglected. It indicates that the (special) relativistic enhancement expected is lost to the (general) relativistic increase of angular momentum after incorporating the effect of mass.