Effect of Radiative Levitation on Calculations of Accretion Rates in White Dwarfs Pierre Chayer 1 and Jean Dupuis 2 1 STScI, 2 CSA 17 th European White Dwarf Workshop Tübingen, Germany August 16−20, 2010 Gemini Observatory Illustration by Jon Lomberg

Two methods exist for computing accretion rates 2 1)Steady state approximation 2)Time-dependent diffusion calculations

Silicon and aluminum are supported 3 Radiative acceleration as a function of depth T eff = 20,000 K, log g = 8.0

Silicon is supported in DA with T eff < 17,500 K 4 Radiative acceleration as a function of depth for Si Log g = 8.0

Evolution of Si in a DA in presence of accretion but without radiative levitation 5 Log [dM/dt] Si = 10 2 g/s, T eff = 20,000 K, log g = 8.0

Evolution of Si in a DA in presence of accretion and radiative levitation 6 Log [dM/dt] si = 10 2 g/s, T eff = 20,000 K, log g = 8.0

Evolution of Si in a DA in presence of accretion and radiative levitation 7 Log [dM/dt] si = 10 6 g/s, T eff = 20,000 K, log g = 8.0

The radiative levitation has an impact on the determination of accretion rates 8 Silicon abundance as a function of depth Teff = 20,000 K Log g = 8.0

In summary, the abundance of elements supported by the radiative levitation may not be related to the accretion rate 9 25,000 K 20,000 K 17,500 K 22,500 K Log g = 8.0