A Polarimetric Method of Measuring Radial Velocities

Abstract

Stellar light approaching the spectrometer slit is artificially polarized in such a way that the plane of linear polarization changes rapidly with wavelength. For each resolution element in the spectrum a photon-counting image tube measures the intensity of the light and the position angle of its polarization. Wavelengths determined from these position angles are independent of the position of the stellar image on the spectrometer slit; therefore a wide open slit can be used for radial velocity measurements. An echelle spectrometer on an 80-inch telescope is expected to give a radial velocity accurate to ± 1 km sec -1 in about four minutes of observing the profile of a spectral line of a 10th magnitude star.

Compact and robust method for full Stokes spectropolarimetry

“…These two approaches, as well as a number of technical issues that arise in each case, are described in some detail in [2]. Previous authors have used multiorder retarders, birefringent wedges, pairs of birefringent wedges, and Savart plates individually or in combination for these two applications [5,[7][8][9][10][11][12][13][14][15][16]. Typically, the polarization information is extracted from the data using Fourier methods.…”

Stellar Spectroscopy Technique on Small- and Intermediate-Diameter Telescopes

“…With low-resolution observations it was planned to use interferograms directly for the classification of spectra (observations were made in the pre-computer era). Serkowski [176] proposed a method for studying the distribution of radial velocities in extended objects with emission-line spectra. The line studied is separated by an interference filter and then light passes through the polarization interferometer and is then registered by a field detector.…”