INTEGRAL ISGRI 4-Year Source Catalog

Follow-up observations at other wavelengths revealed that some of these sources feature unusually large column densities, long pulsations, and other interesting characteristics. The authors investigated where new and previously-known sources detected by ISGRI fit in the parameter space of high-energy objects, and they used the parameters to test correlations expected from theoretical predictions.

For example, the influence of the local absorbing matter on periodic modulations was studied for Galactic High-Mass X-ray Binaries (HMXBs) with OB supergiant and Be companions. In their paper, they examined the spatial distribution of different types of sources in the Milky Way, using various projections of the Galactic plane, in order to highlight signatures of stellar evolution and to speculate on the origin of the group of sources whose classifications were still uncertain.