  The distribution of the circumstellar material in systems of supergiant X-ray
binaries (SgXBs) is complex and not well probed observationally. We report a
detailed study of the spatial distribution of the Fe K{\alpha}-emitting
material in the wind-fed system GX 301-2, by measuring the time delay between
the Fe K{\alpha} line and the hard X-ray continuum (7.8-12 keV) using the
cross-correlation method, based on XMM-Newton observation. We found that to
obtain the true time delay, it is crucial to subtract the underlying continuum
of the Fe K{\alpha} line. The measured size of the Fe K{\alpha}-emitting region
over the whole observation period is 40 {\pm} 20 light-seconds. It is 5 times
larger than the accretion radius estimated from a quasi-isotropic stellar wind,
but consistent with the one estimated from a tidal stream, which could be the
dominant mass-loss mechanism of GX 301-2 as inferred from the orbital
distribution of the absorption column density previously. The measured time
delay of the quiescent period is a little smaller than those of the flare
periods, revealing the unsteady behaviour of the accretion flow in GX 301-2.
Statistical and detailed temporal studies of the circumstellar material in
SgXBs are expected for a large sample of SgXBs with future X-ray missions, such
as Athena and eXTP.
