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arXiv · 1506.01585

A new nonlocal thermodynamical equilibrium radiative transfer method for cool stars

Julien Lambert·Eric Josselin·Nils Ryde·Alexandre Faure
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Abstract

Context: The solution of the nonlocal thermodynamical equilibrium (non-LTE) radiative transfer equation usually relies on stationary iterative methods, which may falsely converge in some cases. Furthermore, these methods are often unable to handle large-scale systems, such as molecular spectra emerging from, for example, cool stellar atmospheres. Aims: Our objective is to develop a new method, which aims to circumvent these problems, using nonstationary numerical techniques and taking advantage of parallel computers. Methods: The technique we develop may be seen as a generalization of the coupled escape probability method. It solves the statistical equilibrium equations in all layers of a discretized model simultaneously. The numerical scheme adopted is based on the generalized minimum residual method. Result:. The code has already been applied to the special case of the water spectrum in a red supergiant stellar atmosphere. This demonstrates the fast convergence of this method, and opens the way to a wide variety of astrophysical problems.

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Julien Lambert, Eric Josselin, Nils Ryde, Alexandre Faure. 2015-06-04. A new nonlocal thermodynamical equilibrium radiative transfer method for cool stars. https://doi.org/10.1051/0004-6361/201322852

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