Stellar-wind bubble
Stellar-wind bubbles have a two-shock structure. The freely-expanding stellar wind hits an inner firing shock, where its kinetic energy is thermalized, producing 106 K, X-ray-emitting plasma.  The hot, high-pressure, shocked wind expands, driving a shock into the surrounding interstellar gas. If the surrounding gas is dense enough (number densities  or so), the swept-up gas radiatively cools far faster than the hot interior, forming a thin, relatively dense shell around the hot, shocked wind.