Symbiotic novae are slow irregular eruptive variable stars with very slow nova-like outbursts of 9-11 amplitude 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,[1] and one white dwarf, with markedly contrasting spectrae and whose proximity and mass characteristics indicate it as a symbiotic star. The red giant fills its Roche lobe so that matter transfers to the white dwarf and accumulates until the nova-like outburst 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.[2]
It is believed that the white dwarf component of the symbiotic novae remain below the Chandrasekhar limit, so that they remain white dwarfs after their outbursts.[2]
One example of a symbiotic nova is V1016 Cygni, whose outburst in 1971-2007 clearly indicated a thermonuclear explosion.[3] Other examples are HM Sagittae and RR Telescopii.[1]