The Galway Astronomical Stokes Polarimeter: An All-Stokes Optical Polarimeter with Ultra-High Time Resolution

Abstract

Many astronomical objects emit polarised light, which can give information both about their source mechanisms, and about (scattering) geometry in their source regions. To date (mostly) only the linearly polarised components of the emission have been observed in stellar sources. Observations have been constrained because of instrumental considerations to periods of excellent observing conditions, and to steady, slowly or periodically-varying sources. This leaves a whole range of interesting objects beyond the range of observation at present. The Galway Astronomical Stokes Polarimeter (GASP) has been developed to enable us to make observations on these very sources. GASP measures the four components of the Stokes Vector simultaneously over a broad wavelength range 400-800nm., with a time resolution of order microseconds given suitable detectors and a bright source - this is possible because the optical design contains no moving or modulating components. The initial design of GASP is presented and we include some preliminary observational results demonstrating that components of the Stokes vector can be measured to <1% in conditions of poor atmospheric stability. Issues of efficiency and stability are addressed. An analysis of suitable astronomical targets, demanding the unique properties of GASP, is also presented.

21 pages; 12 figures accepted for publication by Experimental Astronomy

References in corpus (3)

• Optical polarisation of the Crab pulsar: precision measurements and comparison to the radio emission
• Optical pulsations from the anomalous X-ray pulsar 1E 1048.1-5937
• The Optical Polarisation of the Vela Pulsar revisited

Cited by in corpus (8)

• A recent change in the optical and γ-ray polarization of the Crab nebula and pulsar
• HST optical polarimetry of the Vela pulsar & nebula
• The INTEGRAL view of the pulsating hard X-ray sky: from accreting and transitional millisecond pulsars to rotation-powered pulsars and magnetars
• Circular polarisation of synchrotron radiation in high magnetic fields
• Optical polarimetry: Methods, Instruments and Calibration Techniques
• A Decade of Linear and Circular Polarimetry with the POLISH2 Polarimeter
• An investigation of the Eigenvalue Calibration Method (ECM) using GASP for non-imaging and imaging detectors
• Robust polarimetry via convex optimization