Investigating Pulse Morphology in GX 1+4

Storey, Michelle C.
Greenhill, J.G.
Kotani, T.

Special Research Centre for Theoretical Astrophysics,
School of Physics, University of Sydney, NSW, 2006, Australia
m.storey@physics.usyd.edu.au
Department of Physics,
University of Tasmania, GPO Box 252C, Hobart, 7001, Australia
John.Greenhill@utas.edu.au
Cosmic Radiation Laboratory
The Institute of Physical and Chemical Research (RIKEN)
2-1, Hirosawa, Wako, Saitama 351-01 Japan

Abstract:

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 probablilities 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.

Keywords::radiation mechanism: non-thermal - pulsars: individual(GX 1+4) - X-rays: stars

© Copyright Astronomical Society of Australia 1997