Recovering polarized intensity distribution at diffraction limited resolution using differential speckle polarimetry

Here we demonstrate how diffraction limited polarized flux imaging at single filled-aperture telescope can be implemented using an instrument combining properties of a speckle interferometer and dual—beam polarimeter. By processing of a series of short-exposure, seeing limited images of an object obtained at orthogonal polarizations simultaneously the ratio of its visibilities at orthogonal polarizations is estimated. Two such differential polarimetric visibilities can be defined: for Stokes Q and U; both the amplitude and argument of them are being estimated. Assuming that the object under study is dominated by unpolarized unresolved source, e.g. star, the image of polarized circumstellar envelope can be recovered from the described ratio of visibilities. With wpeckle polarimeter, an instrument implementing DSP at 2.5-m SAI MSU telescope, differential polarimetric visibility can be measured with precision of 2.2 10−3 for Rc = 6 star in 150 sec of accumulation. This precision is significantly higher than precision of visibility measurement using conventional speckle interferometry in the same conditions. Using laboratory measurements we show that in current design differential polarization aberrations of instrument and telescope do not limit the precision of instrument for targets fainter than Rc = 6. The latter is mainly defined by photon noise and detector noise.