Skip to Main content Skip to Navigation
Journal articles

New boundary conditions for the approximate flux-limited diffusion radiative transfer in circumstellar environments. Test case study for spherically symmetric envelopes

Abstract : Context. In order to constrain the models describing circumstellar environments, it is necessary to solve the radiative transfer equation in the presence of absorption and scattering, coupled with the equation for radiative equilibrium. However, solving this problem requires much CPU time, which makes the use of automatic minimisation procedures to characterise these environments challenging. Aims. In this context, the use of approximate methods is of primary interest. One promising candidate method is the flux-limited diffusion (FLD), which recasts the radiative transfer problem into a non-linear diffusion equation. One important aspect for the accuracy of the method lies in the implementation of appropriate boundary conditions (BCs). We present new BCs for the FLD approximation in circumstellar environments that we apply here to spherically symmetric envelopes. Methods. At the inner boundary, the entering flux (coming from the star and from the envelope itself) may be written in the FLD formalism and provides us with an adequate BC. At the free outer boundary, we used the FLD formalism to constrain the ratio of the mean radiation intensity over the emerging flux. In both cases we derived non-linear mixed BCs relating the surface values of the mean specific intensity and its gradient. We implemented these conditions and compared the results with previous benchmarks and the results of a Monte Carlo radiative transfer code. A comparison with results derived from BCs that were previously proposed in other contexts is presented as well. Results. For all the tested cases, the average relative difference with the benchmark results is below 2% for the temperature profile and below 6% for the corresponding spectral energy distribution or the emerging flux. We point out that the FLD method together with the new outer BC also allows us to derive an approximation for the emerging flux. This feature avoids additional formal solutions for the radiative transfer equation in a set of rays (ray-tracing computations). Conclusions. The FLD approximation together with the proposed new BCs performs well and captures the main physical properties of the radiative equilibrium in spherical circumstellar envelopes.
Document type :
Journal articles
Complete list of metadata

https://hal.archives-ouvertes.fr/hal-03306454
Contributor : Jérémy Perdigon <>
Submitted on : Thursday, July 29, 2021 - 10:19:58 AM
Last modification on : Wednesday, September 15, 2021 - 8:48:03 AM

File

aa40236-20.pdf
Files produced by the author(s)

Identifiers

Collections

Citation

J. Perdigon, G. Niccolini, M. Faurobert. New boundary conditions for the approximate flux-limited diffusion radiative transfer in circumstellar environments. Test case study for spherically symmetric envelopes. Astronomy and Astrophysics - A&A, EDP Sciences, 2021, ⟨10.1051/0004-6361/202040236⟩. ⟨hal-03306454⟩

Share

Metrics

Record views

42

Files downloads

60