Mixing in classical nova outbursts

Classical novae are stellar explosions in close binary systems, driven by mass transfer episodes. The material piles up under degenerate conditions, and a thermonuclear runaway (TNR) reaching T_peak ∼ (1-4)×10 ⁸ K ensues. In the explosion, about 10^-4-10 ^-5M_⊙ are ejected into the interstellar medium, containing large amounts of ¹³C, ¹⁵N, and ¹⁷O. To account for the energetics of the explosion as well as for the inferred abundance pattern, mixing at the core-envelope interface has been invoked. Over 40 years, theoreticians have been exploring different mixing mechanisms that could lead to the observed metallicity enhancement in the ejecta. In this study we show that Kelvin-Helmholtz instabilities can naturally dredge up carbon and oxygen from the outer layers of the with dwarf core, leading to a final envelope metallicity above 0:20.