CMFGEN - GREAT-ESF Stellar Atmospheres in the Gaia Era ...

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CMFGEN - GREAT-ESF Stellar Atmospheres in the Gaia Era ...

1. The radiative transfer code CMFGEN

Linearization of rate equations

Consider a function of 1 variable. In general the equation can be written as:

f(x)=0

For some estimate x1, f(x1) ≠ 0. We can compute a correction Δx using a

Taylor expansion. To first order, we require:

0=f(x1)+ Δx f’(x1) (‘ denotes derivative)

This gives

Δx=-f(x1)/f’(x1)

Thus:

x2 = x1 - (-Δx)

This can be easily extended to more than one variable:

note: B = BA, F=STEQ in CMFGEN

Jose Groh - Modeling the wind and photosphere of massive stars with CMFGEN GREAT-ESF workshop, Brussels, 24 June 2011

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