Boris Safonov

Post-Doctoral Researcher

Differential polarimetry at diffraction limited resolution

Interferometry -- Polarimetry -- YSO

Current Research Summary:

Nowadays differential polarimetry is actively used to improve the contrast provided by a coronagraph at the distance from the bright source several times larger than the Airy disk size. However, apart from that, differential polarimetry have great potential for study of spatial structures at the distance from the star comparable and smaller than the Airy disk size. The corresponding method is so called polarimetric interferometry.
Our understanding of bright inner parts of circumstellar environment of young stars and evolved stars would benefit greatly from polarimetric interferometry. In the future, it may also be useful for studying active galactic nuclei and supernovae. Generally speaking, in all cases when polarigenic mechanism is not entirely clear, the localization of source of polarized light at the highest possible angular resolution may be the key.
For the development of high angular resolution polarimetry I with my colleagues at SAI MSU designed and constructed a specialized instrument: speckle polarimeter. It is a combination of a two-beam polarimeter with rotating half-wave plate and a EMCCD-based speckle interferometer. Speckle polarimeter is used for regular observations at 2.5 m telescope of SAI MSU.
The basic observable which is measured with this instrument is the ratio of visibilities in orthogonally polarized light. This quantity can be measured with much greater accuracy than the visibility itself thanks to differential polarimetric approach. Using speckle polarimeter even at the telescope of modest size and without AO we managed to obtain some interesting results: 1) Discovery of a nebula at 0.15" to the south of mu Cep. 2) Tracing the protoplanetary disk (or probably a disk wind?) of RY Tau down to distances of 0.05" from the star. 3) Discovery of mysterious variable nebula around V CVn. More to come.

Prior Research:

AO simulation, MASS-DIMM turbulence profiler