The contribution of light bending and redshift to the pulse characteristics of a pulsar in the case of smaller neutron stars

Abstract

The effect of light bending and redshift on pulsar beam characteristics is estimated using the weak form of the Kerr metric applicable to a slow-rotating neutron star. The beam is found to diverge by a factor of 2 or less and to suffer an intensity reduction by an order of magnitude when emitted from close to the star's surface. This flattening of the pulse profile is strongest for the smallest of the neutron stars and becomes insignificant for emission points located beyond about 20 km for all the neutron star radii considered. For a given emission location, the divergence is comparatively greater in the Schwarzschild background than in the rotational case. Although the pulse must brighten up, a large redshift factor overcomes this to keep the pulse profile flattened. For a period of 1.56 ms, a squeezing is noticeably present at emission points about 500 km from the star's surface. For the same radial location, the squeezing is found to be less severe for emission at lesser inclination angles.