Speaker
Description
Classical-nova outbursts are thermonuclear explosions in the accreted envelope of a white dwarf in a close, mass-transferring binary system. Three-dimensional nova studies show that temperature fluctuations during the explosions cause dredge up of white-dwarf material that enriches nova ejecta up to about 60% metals. Conventionally, white-dwarf-envelope interface mixing is not modelled in 1D simulations of novae. Instead, pre-mixed material is accreted resulting in a less-massive envelope at explosion. In this talk I will present an imposed-diffusive mixing method of WD-envelope mixing during a nova's thermonuclear runaway, as developed for MESA by Arman Aryaeipour in his PhD.
With this method, Solar-composition material is accreted then mixing is parameterized based on 3D hydrodynamics. We construct a parameter space of nova outbursts to investigate the impact of WD mass, composition and mixing on key nova features and nucleosynthetic yields. We show that realistic multiple outbursts differ from individual explosions, and that our novae eject 1-2 orders of magnitude less beryllium-7, hence less lithium-7, than predicted in the literature, disagreeing with idea that novae make much Galactic lithium. The uncertainties are large but now quantifiable, with variable accretion rates and chemical diffusion at the white-dwarf-envelope interface leading to a wide range of ejected metallicities, sometimes up to 50%, much of which can be lithium-7.
