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A new nonlocal thermodynamical equilibrium radiative transfer method for cool stars Method and numerical implementation

Lambert, Julien LU ; Josselin, E.; Ryde, Nils LU and Faure, A. (2015) In Astronomy & Astrophysics 580.
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... (More)
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. Results. 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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
radiative transfer, stars: atmospheres, methods: numerical
in
Astronomy & Astrophysics
volume
580
publisher
EDP Sciences
external identifiers
  • wos:000360020200050
  • scopus:84938304819
ISSN
0004-6361
DOI
10.1051/0004-6361/201322852
language
English
LU publication?
yes
id
77ba4d29-c448-423c-aa2d-52c6b14922a8 (old id 8080488)
date added to LUP
2015-10-26 14:55:42
date last changed
2017-01-01 05:56:11
@article{77ba4d29-c448-423c-aa2d-52c6b14922a8,
  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. Results. 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.},
  articleno    = {A50},
  author       = {Lambert, Julien and Josselin, E. and Ryde, Nils and Faure, A.},
  issn         = {0004-6361},
  keyword      = {radiative transfer,stars: atmospheres,methods: numerical},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {A new nonlocal thermodynamical equilibrium radiative transfer method for cool stars Method and numerical implementation},
  url          = {http://dx.doi.org/10.1051/0004-6361/201322852},
  volume       = {580},
  year         = {2015},
}