Colliding-wind binary

A colliding-wind binary is a binary star system in which the two members are massive stars that emit powerful, radiatively-driven stellar winds. The location where these two winds collide produces a strong shock front that can cause radio, X-ray and possibly synchrotron radiation emission.^[1] Wind compression in the bow shock region between the two stellar winds allows dust formation. When this dust streams away from the orbiting pair, it can form a pinwheel nebula of spiraling dust. Such pinwheels have been observed in the Quintuplet Cluster.^[2]

A composite optical/x-ray image of Eta Carinae and its surrounding nebula taken by the Chandra X-ray Observatory and the Hubble Space Telescope. The blue inner part of the nebula is optical emission, powered by the collision of winds from Eta Carinae and its unseen companion.^[3] Credit: Chandra Science Center and NASA.

The archetype of such a colliding-wind binary system is WR 140 (HD 193793), which consists of a 20 solar mass (M_☉) Wolf-Rayet star orbiting about a 50 M_☉, spectral class O4–5 main sequence star every 7.9 years. The high orbital eccentricity of the pair allows astronomers to observe changes in the colliding wind region as their separation varies.^[4][5] Another prominent example of a colliding-wind binary is thought to be Eta Carinae, one of the most luminous objects in the Milky Way galaxy.^[6] The first colliding-wind binary to be detected in the X-ray band outside the Milky Way galaxy was HD 5980, located in the Small Magellanic Cloud.^[7]

See also

• Struve-Sahade effect
• Cosmic wind
• Stellar wind
• Solar wind
• Planetary wind
• Stellar-wind bubble
• Pulsar wind nebula
• Galactic superwind
• Superwind