The Effect of Multiple Scattering on the Polarization
from Binary Star Envelopes

I. Self- and Externally-Illuminated Disks

Jennifer L. Hoffman, Barbara A. Whitney, and Kenneth H. Nordsieck

2003 ApJ, 598, 572

Summary of results

 
We present the results of a Monte Carlo radiative transfer code that calculates the polarization produced by multiple Thomson scattering and variable absorptive opacity in a circumstellar disk around one component of a close detached binary system. We consider in detail the polarization variations over the binary cycle that result from the disk's illumination both by the external star and by its own volume emission. We identify key features of these polarization phase curves and investigate their behavior as functions of optical depth, albedo, and inclination for geometrically thin and thick disks. The polarization due to disk self-illumination is sensitive to the internal optical characteristics of the disk, while the polarization arising from external illumination is mainly sensitive to the disk's geometrical thickness. With appropriate flux weighting, these results, combined with those for an internally illuminated disk, allow simulation of the polarization signature from an arbitrary binary-disk system.
 

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March 24, 2004