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DC Field | Value | Language |
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dc.contributor.author | Nagendra, K. N | - |
dc.contributor.author | Leung, C. M | - |
dc.date.accessioned | 2008-07-22T11:51:57Z | - |
dc.date.available | 2008-07-22T11:51:57Z | - |
dc.date.issued | 1996-08 | - |
dc.identifier.citation | Monthly Notices of the Royal Astronomical Society, Vol. 281, No. 4, pp. 1139 - 1164 | en |
dc.identifier.issn | 0035-8711 | - |
dc.identifier.uri | http://hdl.handle.net/2248/2826 | - |
dc.description.abstract | Radiation transport models are constructed for the dust shells of the hydrogen deficient supergiant star R Coronae Borealis (R CrB). IRAS observations of R CrB are used as constraints in selecting the model parameters. Based on suggestions from earlier work, a double-shell model is employed as a standard configuration for R CrB. The first shell is a hot inner shell of radius 5 arcsec surrounding the central star. The second shell is a cold remnant shell which is highly extended, with a radius of 10 arcmin (derived assuming a source distance of 1.6 kpc). The two shells can be spatially separated, and can have completely different mechanisms for the heating of their dust grains. A detailed parametric study of the system is undertaken using simple power law density and opacity for single sized grains. The models of R CrB clearly point to the configuration of a large well-separated cold dust shell surrounding a tiny hot dust shell, which supports the existing view that this extended shell is a fossil shell. However, the separation between the two shells cannot be determined purely from the radiative transfer modelling. This can still be treated as a free parameter of the system for modelling purposes. The interstellar radiation field (ISRF) incident on the outer boundary of the system plays a considerable role in explaining the 60- and 100-μm surface brightness of R CrB measured by IRAS. The observed constant temperature of the fossil shell, however, poses serious theoretical problems. We propose models in which the density varies as r^-gamma (gamma~=1.0-1.5). The source of dust heating in our models is a combination of central star radiation and ISRF. The amorphous carbon grains seem to give better fits to the IRAS data than the crystalline grains do. A comparison of both the analytic models and the radiative transfer models is made, to clarify their usefulness in modelling the density and the surface brightness data of R CrB. The models are schematic in nature, and are not intended as best fitting models for the R CrB fossil shell. | en |
dc.format.extent | 3044398 bytes | - |
dc.format.mimetype | application/pdf | - |
dc.language.iso | en | en |
dc.publisher | Royal Astronomical Society | en |
dc.relation.uri | http://adsabs.harvard.edu/abs/1996MNRAS.281.1139N | en |
dc.subject | Radiative transfer | en |
dc.subject | Circumstellar matter | en |
dc.subject | Stars: individuals : R coronae borealis | en |
dc.subject | Dust | en |
dc.subject | Extinction | en |
dc.subject | Infrared:stars | en |
dc.title | Models of highly extended dust shells around R Coronae Borealis | en |
dc.type | Article | en |
Appears in Collections: | IIAP Publications |
Files in This Item:
File | Description | Size | Format | |
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nagendra.pdf | 2.97 MB | Adobe PDF | View/Open |
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