What is "symbiotic star"

n. (context astronomy English) A double star system, in which a cool star is within the nebula of a hot star

A symbiotic star is a type of binary star. They are usually a white dwarf with a companion late sequence red giant. They are indicated by the exhibition of spectral lines of the highly contrasting temperatures of the red giant (~3000 K) and the white dwarf (~20 000 K). The white dwarf gains mass from stellar wind from the red giant or gravitational streaming.

Symbiotic stars are of particular interest to astronomers as they can be used to learn about stellar evolution. They are also vital in the study of stellar wind, ionized nebulae, and accretion because of the unique interstellar dynamics present within the system.