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Neutron star Z type sources provide a unique platform in order to understandthe structure of accretion disk-corona geometry emitting close to the Eddingtonluminosity. Using RXTE and NuSTAR satellite data, we performed crosscorrelation function (CCF) studies in GX 17+2 in order to constrain the size ofcorona responsible for hard X-rays. From the RXTE data, we found that duringhorizontal and normal branches, the CCFs show anti-correlated hard (16 - 30keV) and soft (2 - 5 keV) X-ray delays of the order of a few tens to hundredseconds with a mean correlation coefficient of 0.42$\pm$0.11. Few observationsshows correlated lags and on one occasion coincident with radio emission. Wealso report an anti-correlated hard X-ray delay of 113$\pm$51 s using theNuSTAR data of GX 17+2. Based on RXTE data, it was found that soft and hardX-ray fluxes are varying indicating the changes in the disk-corona structureduring delays. We bridle the size of corona using relativistic precession,transition layer and boundary layer models. Assuming the delays to bereadjustment time scale of disk-corona structure, height of the corona wasestimated to be $\sim$ 17--100 km. Assuming that inner region of the truncateddisk is occupied by the corona, we constrain the coronal readjustmentvelocities (v$_{corona}$=$\beta$ v$_{disk}$, where v$_{disk}$ is the radialvelocity component of the disk) of the order of $\beta$=0.06-0.12. This studyindicates that the observed delays are primarily dependent on the varyingcoronal readjustment velocities.

Constraining the Coronal Heights and Readjustment Velocities Based on the Detection of a Few Hundred Seconds Delays in the Z Source GX 17+2