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Polarized Continuum Radiation from Stellar Atmospheres

Published online by Cambridge University Press:  24 July 2015

J. Patrick Harrington
J. Patrick Harrington*
Affiliation:
Dept. of Astronomy, University of Maryland College Park, MD 20742, USA email: [email protected]
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Abstract

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Continuum scattering by free electrons can be significant in early type stars, while in late type stars Rayleigh scattering by hydrogen atoms or molecules may be important. Computer programs used to construct models of stellar atmospheres generally treat the scattering of the continuum radiation as isotropic and unpolarized, but this scattering has a dipole angular dependence and will produce polarization. We review an accurate method for evaluating the polarization and limb darkening of the radiation from model stellar atmospheres. We use this method to obtain results for: (i) Late type stars, based on the MARCS code models (Gustafsson et al. 2008), and (ii) Early type stars, based on the NLTE code TLUSTY (Lanz and Hubeny 2003). These results are tabulated at http://www.astro.umd.edu/~jph/Stellar_Polarization.html While the net polarization vanishes for an unresolved spherical star, this symmetry is broken by rapid rotation or by the masking of part of the star by a binary companion or during the transit of an exoplanet. We give some numerical results for these last cases.

Keywords

polarizationradiative transferastronomical data bases: miscellaneousstars: atmospheresbinaries: eclipsingplanetary systems
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 10 , Symposium S305: Polarimetry: From the Sun to Stars and Stellar Environments , December 2014 , pp. 395 - 400
Copyright
Copyright © International Astronomical Union 2015 

References

Gustafsson, B., Edvardsson, B., Eriksson, K., Jørgensen, U. G., Nordlund, Å., & Plez, B. 2008, A&A 486, 951 Google Scholar
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Kostogryz, N. M. & Berdyugina, S. V. 2015, A&A 575, A89 Google Scholar
Lanz, T. & Hubeny, I. 2003, ApJS 146, 417 Google Scholar