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   PR # 21037
    We propose pulse phase spectroscopy of the X-ray pulsar GX 1+4.Measur
    ements of the iron emission lines and edge will be used to determine 
    the ionisation state and distribution of circumstellar iron.This will
    enable us to constrain the diameter of the neutron star magnetosphere
    and hence to distinguish between high and low magnetic field models  
    of GX 1+4.The spectra will also be used to test pulsar emission theor
    ies and to improve parameterisation of the system.  Gravitational    
    efects will be included in the modelling. Near simultaneous optical &
    X-ray spectroscopy will provide information about the circumstellar  
    matter and shed light on the mechanisms of the recent outburst.  Prog
    rams of optical spectroscopy and photometry, to determine the orbital
   period, have already commenced
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