Performance analysis of differential speckle polarimetry

We consider a method for obtaining information on polarization of astronomical objects radiation at diffraction limited resolution—differential speckle polarimetry. As an observable we propose to use averaged cross spectrum of two short-exposure images corresponding to orthogonal polarizations, normalized by averaged power spectrum of one of images. Information on polarization can be extracted if object under study can be described by model with several parameters. We consider two examples: pointlike source whose photocenter position depends on orientation of passing polarization and exozodiacal dust disc around a star. In first case the difference between photocenter positions can be measured with precision of 8 µas for 2.5-m telescope and 1.2 µas for 6-m telescope for object V = 13 ^m . For second example method allows detection of discs around central star of V = 1 ^m with fractional luminosities of 1.8 × 10^?5 and 5.6 × 10^?6 for 2.5- and 6-m telescope, respectively.