共生变星是喷发非常缓慢的不规则变星，很像慢新星，爆发的星等振幅在9-11等级之间。共生变星会维持它的最大光度十年乃至数十年，然后下降至它原来的光度。这种类型的变星是联星系统，其中一颗是可能是米拉变星的红巨星，另一颗是白矮星。明显对比的光谱和相当的接近与质量等特征，显示它们是共生的恒星。红巨星充满了它的洛希瓣，因此造成物质溢流转移到白矮星和吸积，直到点燃了热核反应，引起类新星的爆发。估计最高温度可以上升到200,000K，类似于新星的能量来源，但不同于矮新星。缓慢增加的光度只是单纯的因为在爆发之前需要时间成长出足够的电离前缘。

Symbiotic novae are slow irregular eruptive variable stars with very slow nova-like outbursts with an amplitude of between 9 and 11 magnitudes. The symbiotic nova remains at maximum for one or a few decades, and then declines towards its original luminosity. Variables of this type are double star systems with one red giant, which probably is a Mira variable, and one white dwarf, with markedly contrasting spectra and whose proximity and mass characteristics indicate it as a symbiotic star. The red giant fills its Roche lobe so that matter is transferred to the white dwarf and accumulates until a nova-like outburst occurs, caused by ignition of thermonuclear fusion. The temperature at maximum is estimated to rise up to 200,000 K, similar to the energy source of novae, but dissimilar to the dwarf novae. The slow luminosity increase would then be simply due to time needed for growth of the ionization front in the outburst.