SETI: September 2016

Suppose that advanced civilizations, separated by a cosmological distance and time, wish to maximize their access to cosmic resources by rapidly expanding into the universe.

If a sufficiently advanced civilization can either modulate the emission from an X-ray binary, or make use of the natural high luminosity to power an artificial transmitter, these can serve as good beacons for interstellar communication without involving excessive energy costs to the broadcasting civilization.