The typical X-ray sources are X-ray binaries in our galaxy. These X-ray binaries are in fact two stars that rotate around each other. One of the two is a normal star. But the other is an odd star, such as a neutron star or black hole, which has about the same mass as our Sun, but has shrunk to ten kilometers or less in radius.
Video shows two stars orbiting each other. The odd star is pulling matter away from the normal star.