  We present the orbital X-ray modulation study of three high mass X- ray
binary systems, IGR J18027-2016, IGR J18483-0311 and IGR J16318-4848 using data
obtained with RXTE-ASM, Swift-BAT and INTEGRAL-ISGRI. Using the long term light
curves of the eclipsing HMXB IGR J18027-2016, obtained with Swift-BAT in the
energy range 15-50 keV and INTEGRAL-ISGRI in the energy range 22-40 keV, we
have determined three new mid eclipse times. The newly determined mid eclipse
times together with the known values were used to derive an accurate value of
the orbital period of 4.5693(4) d at MJD 52168 and an upper limit of
3.9(1.2)x10^-7 d d^-1 on the period derivative. We have also accurately
determined an orbital period of 18.5482(88) d for the intermediate system IGR
J18483-0311, which displays an unusual behaviour and shares many properties
with the known SFXTs and persistent supergiant systems. This is a transient
source and the outbursts occur intermittently at intervals of 18.55 d.
Similarly, in the third supergiant system, IGR J16318-4848, we have found that
the outbursts are separated by intervals of 80 d or its multiples, suggesting a
possible orbital period.
