Caption: "Artist's conception of a black hole with an orbiting binary companion star that exceeds its Roche limit. Mass from the binary companion star is drawn towards the black hole, forming an accretion disk." (Slightly edited.)

Features:

1. In late stellar life, the binary companion star expands and exceeds its Roche limit: the point where its outer mass is equally attracted to the binary companion star and the black hole.

2. The outer mass then flows freely to the black hole forming an accretion disk (while spiraling into the black hole) by the common accretion disk formation processes.

3. The viscous rubbing of the matter on itself during the in-spiral heats the matter to such high temperatures that it becomes an X-ray blackbody radiator.

   Note in the visible band, an accretion disk probably looks blue since its approximate blackbody spectrum rises going blueward to peak in the X-ray band. The image illustrates the blue appearance of an accretion disk.

4. The black hole thus becomes an observable X-ray source.

5. Magnetic fields generated in the accretion disk (and maybe in the black hole itself it is a Kerr-Newman black hole) can also lead to observable relativistic bipolar jets as in the image.

6. Isolated black holes do NOT emit electromagnetic radiation and are nearly unobservable.

   The accretion-from-binary-companion-star process happens to black holes, neutron stars, and white dwarfs.

   But no one's ever imaged the process. One must infer it from other observational evidence.