Barycentre

The barycentre between stars in the Shinrarta Dezhra system appears as both the lines and an X, due to the planets that orbit the barycentre.

A barycentre is a mutual centre of mass around which two or more bodies orbit.

They can be seen on the System Map as lines forming three sides of a rectangle, linking the bodies indirectly. If anything else is orbiting those bodies collectively (as opposed to individually), the barycentre is additionally marked with an X.