Illustration of Fireball Types. Click on image for detail.
Figure caption: Diagram of flares from fireballs with various amounts of
contaminating matter. A clean fireball (left) produces a short, bright flare at
high-energy gamma rays, whereas a dirty fireball (right) produces an extended, weak flare
at X-ray and optical energies. The central contour illustrates the flare of a typical
gamma-ray burst.
Click on image for detail.