A High Precision, Optical Polarimeter to Measure Inclinations of High Mass X-Ray Binaries

TL;DR

This paper introduces a high precision optical polarimeter designed to measure the inclinations of high mass X-ray binaries, enabling more accurate mass estimates of black hole companions.

Contribution

The paper presents the commissioning results of the POLISH instrument, demonstrating its high precision and potential applications in astrophysics.

Findings

Photon shot noise limited precision achieved on standard stars

Polarization measured at part per million level nightly

Systematic effects reduced to less than 1% of polarization

Abstract

We present commissioning data for the POLISH instrument obtained on the Hale 5-m telescope. The goal of this high precision polarimeter is to constrain orbital inclination of high mass X-ray binaries and to therefore obtain independent mass estimates for their black hole companions. We have obtained photon shot noise limited precision on standard stars, and we have measured the polarization of bright stars at the part per million level on a nightly basis. Systematic effects have been reduced to less than 1% of the measured polarization for polarized sources and to the part per million level for weakly polarized sources. The high sensitivity of this instrument to asymmetry suggests that valuable contributions will be made in many other fields, including studies of extrasolar planets, debris disks, and stellar astrophysics.