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

Summary, in English

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.

• Author: Julien Lambert; E. Josselin; Nils Ryde; A. Faure
• Department/s: Lund Observatory - Undergoing reorganization
• Publishing year: 2015
• Language: English
• Publication/Series: Astronomy & Astrophysics
• Volume: 580
• Links: http://dx.doi.org/10.1051/0004-6361/201322852
• Document type: Journal article
• Publisher: EDP Sciences
• Topic: Astronomy, Astrophysics and Cosmology
• Keywords: radiative transfer; stars: atmospheres; methods: numerical
• Status: Published
• Project: VR-projektbidrag: Infraröd spektroskopi - ett nytt fönster mot galaktisk astronomi; Carl-TryggerStiftelse: Water on Stars
• ISBN/ISSN/Other: ISSN: 0004-6361