X-ray dipping in the black hole binary Cygnus X-1 , the Galactic jet source GRO J1655-40 and in low mass X-ray binaries is discussed .
It is shown that spectral analysis strongly constrains emission models .
Measurement of dip ingress/egress times allows the sizes of extended emission regions to be determined , notably for the Accretion Disk Corona which is responsible for Comptonization in X-ray binaries .
In LMXB , the radius of the ADC is shown to be between { \sim 1 \times 10 ^ { 9 } } and { \sim 5 \times 10 ^ { 10 } } cm , an appreciable fraction of the accretion disk radius .
This is inconsistent with Comptonization models requiring a localized Comptonizing region , for example , in the immediate neighbourhood of the neutron star .
Results from a survey of LMXB using ASCA and BeppoSAX reveal an approximate equality between the height of the blackbody emission region on the neutron star and the height of the inner radiatively-supported disk , suggesting either that there is a direct causal link , such as a radial accretion flow between the inner disk edge and the star , or an indirect link , as in the case of accretion flow creep on the surface of the neutron star as suggested by Inogamov & Sunyaev .
Finally , the survey shows that the blackbody can not originate on the accretion disk as the required inner radii in many sources are substantially less than the neutron star radius .