Differential speckle polarimetry at Cassegrain and Nasmyth foci. (arXiv:1812.05139v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Safonov_B/0/1/0/all/0/1">Boris Safonov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lysenko_P/0/1/0/all/0/1">Pavel Lysenko</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goliguzova_M/0/1/0/all/0/1">Maria Goliguzova</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cheryasov_D/0/1/0/all/0/1">Dmitry Cheryasov</a>

Polarimetric interferometry is a method allowing the study of the
distribution of polarized flux at diffraction-limited resolution. Its basic
observable is the ratio $mathcal{R}$ of the visibilities of the object in two
orthogonal polarizations. Here, we demonstrate how this observables can be
measured with the SPeckle Polarimeter (SPP) of the 2.5-m telescope. The SPP is
a combination of a dual-beam polarimeter and an EMCCD-based visible-range
speckle interferometer. We propose a simple method for the correction of
$mathcal{R}$ for the instrumental polarization and polarization differential
aberrations of the telescope. The polarized intensity image can be estimated
from $mathcal{R}$ under the assumption that the object is a point-like
unpolarized source plus a faint extended polarized envelope. The phase of
$mathcal{R}$ can be used for measurement of the polaroastrometric signal – the
difference between the photocentres of orthogonally polarized images of the
object. We investigate both possibilities using observations of unpolarized
stars and stars with a significant polarized circumstellar environment –
$mu$~Cep and RY~Tau.

Polarimetric interferometry is a method allowing the study of the
distribution of polarized flux at diffraction-limited resolution. Its basic
observable is the ratio $mathcal{R}$ of the visibilities of the object in two
orthogonal polarizations. Here, we demonstrate how this observables can be
measured with the SPeckle Polarimeter (SPP) of the 2.5-m telescope. The SPP is
a combination of a dual-beam polarimeter and an EMCCD-based visible-range
speckle interferometer. We propose a simple method for the correction of
$mathcal{R}$ for the instrumental polarization and polarization differential
aberrations of the telescope. The polarized intensity image can be estimated
from $mathcal{R}$ under the assumption that the object is a point-like
unpolarized source plus a faint extended polarized envelope. The phase of
$mathcal{R}$ can be used for measurement of the polaroastrometric signal – the
difference between the photocentres of orthogonally polarized images of the
object. We investigate both possibilities using observations of unpolarized
stars and stars with a significant polarized circumstellar environment –
$mu$~Cep and RY~Tau.

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