Issue |
A&A
Volume 543, July 2012
|
|
---|---|---|
Article Number | A109 | |
Number of page(s) | 4 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/201219394 | |
Published online | 06 July 2012 |
Fast approximation of angle-dependent partial redistribution in moving atmospheres
1 Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029, Blindern, 0315 Oslo, Norway
e-mail: jorritl@astro.uio.no
2 Utrecht University, Postbus 80 000, 3508 TA Utrecht, The Netherlands
3 NASA Ames Research Center, Moffett Field, CA 94035, USA
4 Lockheed Martin ATC, Solar & Astrophysics Lab, Org. H1–12, Bldg. 252, 3251 Hanover Street, Palo Alto, CA 94304–1187, USA
5 NSO/Sacramento Peak, PO Box 62, Sunspot, NM 88349–0062, USA
Received: 12 April 2012
Accepted: 23 May 2012
Aims. Radiative transfer modeling of spectral lines including partial redistribution (PRD) effects requires the evaluation of the ratio of the emission to the absorption profile. This quantity requires a large amount of computational work if one employs the angle-dependent redistribution function, which prohibits its use in 3D radiative transfer computations with model atmospheres containing velocity fields. We aim to provide a method to compute the emission to absorption profile ratio that requires less computational work but retains the effect of angle-dependent scattering in the resulting line profiles.
Methods. We present a method to compute the profile ratio that employs the angle-averaged redistribution function and wavelength transforms to and from the rest frame of the scattering particles. We compare the emergent line profiles of the Mg II k and Lyα lines computed with angle-dependent PRD, angle-averaged PRD and our new method in two representative test atmospheres.
Results. The new method yields a good approximation of true angle-dependent profile ratio and the resulting emergent line profiles while keeping the computational speed and simplicity of angle-averaged PRD theory.
Key words: radiative transfer / methods: numerical
© ESO, 2012
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