Post on 02-Jan-2016
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Effect of Radiative Levitation on Calculations of Accretion Rates in White Dwarfs
Pierre Chayer1 and Jean Dupuis2
1STScI, 2CSA
17th European White Dwarf Workshop
Tübingen, Germany
August 16−20, 2010
Gem
ini O
bser
vato
ry I
llust
ratio
n by
Jon
Lom
berg
Two methods exist for computing accretion rates
2
1) Steady state approximation
2) Time-dependent diffusion calculations
Silicon and aluminum are supported
3Radiative acceleration as a function of depth
Teff = 20,000 K, log g = 8.0
Silicon is supported in DA with Teff < 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 = 102 g/s, Teff = 20,000 K, log g = 8.0
Evolution of Si in a DA in presence of accretion and radiative levitation
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Log [dM/dt]si = 102 g/s, Teff = 20,000 K, log g = 8.0
Evolution of Si in a DA in presence of accretion and radiative levitation
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Log [dM/dt]si = 106 g/s, Teff = 20,000 K, log g = 8.0
The radiative levitation has an impact on the determination of accretion rates
8Silicon abundance as a function of depth
Teff = 20,000 KLog g = 8.0
In summary, the abundance of elements supported by the radiative levitation may not be related to the accretion rate
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25,000 K
20,000 K
17,500 K
22,500 K
Log g = 8.0