A polarimetric determination of binary inclinations - Results for five systems

Abstract

A method is presented for estimating the orbital inclinations of binary systems from phase-locked polarization variations when those variations arise from certain single-scattering processes, principally scattering by optically thin regions of extrastellar material. In the lowest-order approximation the variable polarization, over an orbital period, twice traces out an ellipse in polarization space. The eccentricity of this ellipse is related to the orbital inclination. This relation is shown to be quite general, the only restrictions being that: (1) the photometric variability be small; (2) eclipses of the scattering regions do not occur; and (3) the system have mirror symmetry through the orbital plane. The method is then applied to five binaries with known inclinations: AO Cassiopeiae and u Herculis, for which observations have already been published; and Algol, U Sagittae, and V444 Cygni, for which observations are presented for the first time.