  High Mass X-ray Binary Pulsars (HMXBP), in which the companion star is a
source of supersonic stellar wind, provide a laboratory to probe the velocity
and density profile of such winds. Here, we have measured the variation of the
absorption column density along with other spectral parameters over the binary
orbit for two HMXBP in elliptical orbits, as observed with the Rossi X-ray
Timing Explorer (RXTE) and the BeppoSAX satellites. A spherically symmetric
wind profile was used as a model to compare the observed column density
variations. In 4U 1538-52, we find the model corroborating the observations;
whereas in GX 301-2, the stellar wind appears to be very clumpy and a smooth
symmetric wind model seems to be inadequate in explaining the variation in
column density.
