Pulsational pair-instability supernova

A pulsational pair-instability supernova is a supernova impostor event that generally occurs in stars at around 100 to 130 solar mass (M_☉), as opposed to a typical pair-instability supernova which occurs in stars of 130 to 250 M_☉. Like pair-instability supernovae, pulsational pair-instability supernovae are caused by draining of a star's energy in the production of electron-positron pairs but, whereas a pair-instability supernova completely disrupts the star in a massive supernova, the star's pulsational pair-instability eruption sheds 10–25 M_☉. This generally shrinks it down to a mass of less than 100 M_☉, too small for electron-positron pair creation, where it then undergoes a core-collapse supernova or hypernova. It is possible that this is what occurred during the 1843 eruption of the primary star of the Eta Carinae star system although there is not yet any substantial evidence supporting this.

Gamma rays by stars of fewer than 100 M_☉ are not energetic enough to produce electron-positron pairs. Some of these stars will undergo supernovae at the end of their lives, but the causative mechanisms are unrelated to pair-instability.

In stars of 100–130 M_☉, a pulsational pair-instability supernova can occur. Stars like this are massive enough that the gamma rays are energetic enough to produce electron-positron pairs but it is generally not enough to completely blow up the star. The carbon-burning core compresses and heats up as the electron-positron pairs remove pressure from outwards photons, until the oxygen stored in the core suddenly ignites in a thermal runaway reaction which exerts a pulse outwards, then stabilises. As a result, the likely outcome will be a pulsational pair-instability supernova, in which the star will eject a large amount of its mass, which will generally bring it under 100 M_☉ where it will typically undergo a normal core-collapse supernova. ^[2][1]

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