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   PR # 22066
    X1755-338 is unique among the many LMXRBs that show periodic, but    
    irregular, dips in their X-ray intensities. Unlike the other         
    "dippers", whose variable spectra can be explained as variations in  
    photoelectric absorption, X1755-338 exhibits dips whose depths are   
    energy independent over a broad range of energies. The simplest      
    explanation for this behavior is that the absorbing material is      
    severely underabundant in metals suggesting an unusual evolutionary  
    history for this source. Alternately,approximately energy-independent
     dips can be accomplished with carefully chosen variations in spectra
     with multiple components and normal abundances.With ASCA's spectral 
    resolution and bandpass, these models can easily be tested.          
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