A high-sensitivity polarimeter using a ferro-electric liquid crystal modulator

TL;DR

The paper introduces HIPPI, a high-sensitivity polarimeter utilizing a ferro-electric liquid crystal modulator, capable of precise linear polarization measurements of starlight with minimal polarization sensitivity and high dynamic range.

Contribution

It presents the design, implementation, and performance of HIPPI, a novel high-precision polarimeter with a ferro-electric liquid crystal modulator for astronomical observations.

Findings

Achieves fractional polarization sensitivity of ~4 x 10$^{-6}$

Provides polarization measurements with better than 0.01% precision

Determines the AAT telescope polarization as 48 ± 5 x 10$^{-6}$ in g' band

Abstract

We describe the HIgh Precision Polarimetric Instrument (HIPPI), a polarimeter built at UNSW Australia and used on the Anglo-Australian Telescope (AAT). HIPPI is an aperture polarimeter using a ferro-electric liquid crystal modulator. HIPPI measures the linear polarization of starlight with a sensitivity in fractional polarization of ~4 x 10$^{-6}$ on low polarization objects and a precision of better than 0.01% on highly polarized stars. The detectors have a high dynamic range allowing observations of the brightest stars in the sky as well as much fainter objects. The telescope polarization of the AAT is found to be 48 $\pm$ 5 x 10$^{-6}$ in the g' band.