
%0 Journal Article
%A Storey, Michelle C 
%A Kotani, T 
%A Greenhill, JG 
%T Investigating Pulse Morphology in GX 1+4
%J Publications of the Astronomical Society of Australia
%D 1998/07/01
%V 15
%N 2
%P 217-221
%K 
%R https://doi.org/10.1071/AS98217
%U https://www.publish.csiro.au/paper/AS98217 
%X Observational and theoretical evidence points to the existence of an unusually high magnetic field on GX 1+4. The pulsar is thus an ideal laboratory for studying two-photon cyclotron emission, an important source of photons of frequency significantly less than the cyclotron frequency in X-ray pulsars. Low-frequency approximations to the two-photon cyclotron emission transition probabilities are derived. These are used to calculate the theoretical opening angle of the double-humped pulse shape predicted by the two-photon cyclotron emission model. The theoretical pulse shape, incorporating the effects of gravitational light bending, is compared with observations of GX 1+4. Observed light curves have opening angles consistent with the theoretically predicted maximum value. 
