Performance Analysis of Differential Speckle Polarimetry

TL;DR

This paper introduces a differential speckle polarimetry method to measure polarization of astronomical objects at diffraction-limited resolution, enabling precise photocenter and dust disk detection with small telescopes.

Contribution

The paper presents a novel observational technique using averaged cross spectrum for polarization analysis at diffraction-limited resolution in astronomy.

Findings

Photocenter position can be measured with 8 micro-arcseconds precision on a 2.5-m telescope.

Detection of exozodiacal dust disks around bright stars is feasible with this method.

Method achieves high sensitivity for faint structures around bright objects.

Abstract

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: point-like source whose photocenter position depends on orientation of passing polarization and exozodiacal dust disc around a star. In first case difference between photocenter positions can be measured with precision of 8 mirco-arcseconds for 2.5-m telescope and 1.2 micro-arcseconds for 6-m telescope for object V=13. For second example method allows detection of discs around central star of V=1 with fractional luminosities of 1.8E-5 and 5.6E-6 for 2.5-m and 6-m telescope, respectively.