We report on two ASCA observations of the high-mass X-ray binary pulsar OAO 1657 - 415 .
A short observation near mid-eclipse caught the source in a low-intensity state , with a weak continuum and iron emission dominated by the 6.4-keV fluorescent line .
A later , longer observation found the source in a high-intensity state and covered the uneclipsed through mid-eclipse phases .
In the high-intensity state , the non-eclipse spectrum has an absorbed continuum component due to scattering by material near the pulsar and 80 per cent of the fluorescent iron emission comes from less than 19 lt-sec away from the pulsar .
We find a dust-scattered X-ray halo whose intensity decays through the eclipse .
We use this halo to estimate the distance to the source as 7.1 \pm 1.3 kpc .