ИСТИНА

Differential Speckle Polarimetry is a method of recovery of the polarized flux distribution at high angular resolution from a series of short-exposure seeing-limited images recorded at two orthogonal polarizations simultaneously. We implement the method using specialized instrument - speckle polarimeter, which is a combination of EMCCD-based speckle interferometer and dual-beam polarimeter. As a feeding optics we use 2.5-m telescope of Caucasian Observatory of Lomonosov MSU. The main observable of method is differential polarimetric visibility - the ratio of visibilities for orthogonal polarizations. Assuming that the object is dominated by unpolarized unresolved source, e.g. a star, the image of polarized circumstellar envelope can be recovered from the described ratio of visibilities at diffraction limited resolution, in our case it is 50-80 mas. We reach contrast of 1e-3 for polarized flux for V=7 objects at 0.15 arcseconds from the central source. The method can be used for study of bright, compact circumstellar envelopes, e.g. around young or evolved stars. As an example we demonstrate the analysis of the variability of a spiral feature at 0.1-0.2 arcseconds from young star CQ Tau using multiepoch observations distributed over 5 years.