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   PR # 22068
    Pulse-phase spectroscopy of the continuum and line features of an    
    X-ray pulsar yields information about the emission near the neutron  
    star surface and the scattering or absorption in the circumstellar   
    environment. We propose to observe GX 1+4, a pulsar with an          
    unusually hard X-ray spectrum that has exhibited pulse phase         
    variability. The ASCA/SIS allows measurements with unprecedented     
    spectral range and resolution. If GX 1+4 is in its low state we      
    will search for phase variability in the continuum and iron-line     
    equivalent width to see whether the high state variability           
    persists. If GX 1+4 is in its high state we will extend the          
    observations of the spectral variability to higher continuum         
   energies and higher resolution
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