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Validation of radiative transfer computation with Monte Carlo method for ultra-relativistic background flow

Ishii, Ayako and Ohnishi, Naofumi and Nagakura, Hiroki and Ito, Hirotaka and Yamada, Shoichi (2017) Validation of radiative transfer computation with Monte Carlo method for ultra-relativistic background flow. Journal of Computational Physics, 348 . pp. 612-633. ISSN 0021-9991. https://resolver.caltech.edu/CaltechAUTHORS:20170728-083855687

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Abstract

We developed a three-dimensional radiative transfer code for an ultra-relativistic background flow-field by using the Monte Carlo (MC) method in the context of gamma-ray burst (GRB) emission. For obtaining reliable simulation results in the coupled computation of MC radiation transport with relativistic hydrodynamics which can reproduce GRB emission, we validated radiative transfer computation in the ultra-relativistic regime and assessed the appropriate simulation conditions. The radiative transfer code was validated through two test calculations: (1) computing in different inertial frames and (2) computing in flow-fields with discontinuous and smeared shock fronts. The simulation results of the angular distribution and spectrum were compared among three different inertial frames and in good agreement with each other. If the time duration for updating the flow-field was sufficiently small to resolve a mean free path of a photon into ten steps, the results were thoroughly converged. The spectrum computed in the flow-field with a discontinuous shock front obeyed a power-law in frequency whose index was positive in the range from 1 to 10 MeV. The number of photons in the high-energy side decreased with the smeared shock front because the photons were less scattered immediately behind the shock wave due to the small electron number density. The large optical depth near the shock front was needed for obtaining high-energy photons through bulk Compton scattering. Even one-dimensional structure of the shock wave could affect the results of radiation transport computation. Although we examined the effect of the shock structure on the emitted spectrum with a large number of cells, it is hard to employ so many computational cells per dimension in multi-dimensional simulations. Therefore, a further investigation with a smaller number of cells is required for obtaining realistic high-energy photons with multi-dimensional computations.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.jcp.2017.07.038DOIArticle
http://www.sciencedirect.com/science/article/pii/S0021999117305466PublisherArticle
ORCID:
AuthorORCID
Nagakura, Hiroki0000-0002-7205-6367
Yamada, Shoichi0000-0002-2166-5605
Additional Information:© 2017 Elsevier Inc. Received 16 December 2015, Revised 11 July 2017, Accepted 20 July 2017, Available online 26 July 2017. We are grateful to the anonymous referees for their so fruitful comments on this manuscript. This work was supported by JSPS KAKENHI Grant Number 52638590, a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (24103006, 24740165, and 24244036), and the HPCI Strategic Program of the Japanese MEXT. This work is partly supported by the Grant-in-Aid for Scientific Research (S:16H06341) and the Grant-in-Aid for Young Scientists (B:16K21630) from the MEXT of Japan. H.N. is supported in part by JSPS Postdoctoral Fellowships for Research Abroad No. 27-348, and also supported at Caltech through NSF award No. TCAN AST-1333520. H.I. is supported in part by the RIKEN pioneering project ‘Interdisciplinary Theoretical Science (iTHES)’.
Funders:
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)52638590
Ministry of Education, Culture, Sports, Science, and Technology (MEXT)24103006
Ministry of Education, Culture, Sports, Science, and Technology (MEXT)24740165
Ministry of Education, Culture, Sports, Science, and Technology (MEXT)24244036
Ministry of Education, Culture, Sports, Science, and Technology (MEXT)S:16H06341
Ministry of Education, Culture, Sports, Science, and Technology (MEXT)B:16K21630
Japan Society for the Promotion of Science (JSPS)27-348
NSFAST-1333520
RIKEN Pioneering ProjectUNSPECIFIED
Subject Keywords:Gamma-ray burst; Relativistic jet; Radiative transfer; Monte Carlo method
Record Number:CaltechAUTHORS:20170728-083855687
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170728-083855687
Official Citation:Ayako Ishii, Naofumi Ohnishi, Hiroki Nagakura, Hirotaka Ito, Shoichi Yamada, Validation of radiative transfer computation with Monte Carlo method for ultra-relativistic background flow, Journal of Computational Physics, Volume 348, 1 November 2017, Pages 612-633, ISSN 0021-9991, https://doi.org/10.1016/j.jcp.2017.07.038. (http://www.sciencedirect.com/science/article/pii/S0021999117305466)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79528
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:28 Jul 2017 15:54
Last Modified:03 Oct 2019 18:21

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