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2000MNRAS.319..337C - Mon. Not. R. Astron. Soc., 319, 337-349 (2000/December-1)
Polarization models of young stellar objects - II. Linear and circular polarimetry of R Coronae Australis.
CLARK S., McCALL A., CHRYSOSTOMOU A., GLEDHILL T., YATES J. and HOUGH J.
Abstract (from CDS):
Although surrounded by reflection nebulosity, there is a region of particularly low polarization surrounding R CrA that is best modelled by the canonical bipolar outflow being truncated by an evacuated spherical cavity surrounding the star. The symmetry axis of the nebula appears inclined by 50° to the plane of the sky.
The H-band circular polarimetry of R CrA clearly shows a quadrupolar structure of positive and negative degrees of circular polarization that reach peak magnitudes of ∼5per cent within our limited map. It is shown that spherical MRN grains are incapable of producing this circular polarization given the observed linear polarization of the R CrA system. Instead, scattering from aligned non-spherical grains is proposed as the operating mechanism.
T CrA is a more archetypical bipolar reflection nebula, and this object is modelled as a canonical parabolic reflection nebula that lies in the plane of the sky. The wavelength independence of linear polarization in the T CrA reflection nebula suggests that the scattering particles are Rayleigh sized. This is modelled with the MRN interstellar grain size distribution.
Abstract Copyright: 2000, Royal Astronomical Society
Journal keyword(s): stars: formation - stars: individual: R CrA - stars: individual: T CrA - stars: pre-main-sequence - ISM: individual: NGC 6729 - reflection nebulae
Nomenclature: Fig.4: [CMC2000b] A (Nos A-F).
Simbad objects: 23
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