Recurrent nova

A nova (plural or novas) or classical nova (CN or plural CNe) is an astronomical event that causes the sudden appearance of a bright "new" star, that slowly fades from view over several weeks or many months. Novae should not be confused with other more energetic astronomical phenomena known as supernovae (SNe), which catastrophically destroys massive stars or white dwarfs.

Causes of their dramatic appearance varies depending on the circumstances of their progenitor stars, but they have in common to be close binary stars, where one component is a white dwarf, or that both stars are red dwarfs in the process of merging. Several main sub-classes of novae exist, based on their many different scenarios, being classical novae, recurrent novae (RNe), dwarf novae, luminous red novae. They are together under a group of variable stars collectively known as cataclysmic variable stars, which share some common properties as close binary systems.

Classical novae eruptions are the most common type of novae. They are likely created in a close binary star system consisting of a white dwarf and either a main sequence, sub-giant or red giant star. When the orbital period falls in the range of several days to one day, the white dwarf is sufficiently close to its companion star to start drawing accreted matter onto the white dwarf's surface, which creates a dense but thin atmosphere. This mostly hydrogen atmosphere is thermally heated from the hot white dwarf star, which eventually reaches a critical temperature, and results in a rapid runaway ignition by fusion. From the dramatic and sudden energies created, the now hydrogen-burnt atmosphere is then dramatically expelled into interstellar space, whose brightened envelope is seen as the visible light created from the nova event. A few novae produce short-lived nova remnants, lasting perhaps several centuries. Recurrent nova processes are the same as the classical nova, except that the fusion ignition can be repeated because the companion star can again feed the dense atmosphere of the white dwarf.

...
Wikipedia