An inexpensive liquid crystal spectropolarimeter for the dominion astrophysical observatory plaskett telescope

Abstract

A new, inexpensive polarimetric unit has been constructed for the Dominion Astrophysical Observatory (DAO) 1.8 m Plaskett telescope. It is implemented as a plug-in module for the telescope's existing Cassegrain spectrograph, and it enables medium-resolution (R 4810,000) circular spectropolarimetry of point sources. A dual-beam design, together with fast switching of the wave plate at rates up to 100 Hz and synchronized with charge shuffling on the CCD, is used to significantly reduce instrumental effects and achieve high-precision spectropolarimetric measurements for a very low cost. The instrument is optimized to work in the wavelength range of 4700-5300 \uc5 to simultaneously detect polarization signals in the H\u3b2 line, as well as nearby metallic lines. In this article we describe the technical details of the instrument, our observing strategy, and data reduction techniques, and we present tests of its scientific performance. \ua9 2012. The Astronomical Society of the Pacific.Peer reviewed: YesNRC publication: Ye