Achromatic and super-achromatic zero-order waveplates

Samoylov, A.V.; Samoylov, V.S.; Vidmachenko, A. P.; Perekhod, A.V.

doi:10.1016/j.jqsrt.2003.12.034

Cited by 48 publications

(18 citation statements)

References 3 publications

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“…We use spectra of the same star obtained with two different instruments: the HARPS polarimeter Piskunov et al 2011) at the ESO 3.6 m telescope, and the SOFIN polarimeter at the 2.56 m NOT (described in the following section). The HARPS polarimeter consists of two exchangeable superachromatic PMMA quarter and half-wave retarders (Samoylov et al 2004) on a rotary stage in front of the Foster prism fixed with respect to two entrance fibers of the spectrograph. The whole setup is located in the F/8 converging beam of the Cassegrain focus of the telescope.…”

Section: Polarization Performance Of Two Instrumentsmentioning

confidence: 99%

Second‐order error propagation in the Mueller matrix of a spectropolarimeter

Ilyin

2012

Astron Nachr

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Accurate measurements of Stokes IQUV in spectral lines is required for precise reconstruction of stellar magnetic field geometries with Zeeman-Dopper imaging. Spectral Zeeman features are intrinsically weak and subjected to a number of instrumental uncertainties. The aim of this work is to study the details of the instrumental uncertainties in the Stokes IQUV measurements in spectral lines and ways of their reduction. We make a practical comparison of the polarimetric performances of two high-resolutionéchelle spectropolarimeters, namely SOFIN at the NOT, and HARPS at ESO. We show the residual spectra for both instruments to characterize the cross-talk between the observed Stokes parameters. We employ a self-calibrating least-squares fit to eliminate some of the polarization uncertainties to derive the full Stokes vector from stellar spectra.

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Section: Polarization Performance Of Two Instrumentsmentioning

confidence: 99%

Second‐order error propagation in the Mueller matrix of a spectropolarimeter

Ilyin

2012

Astron Nachr

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“…The circular polarimeter has a quarter-wave plate and the linear polarimeter is equipped with a half-wave plate. The wave plates used in HARPSpol are zero-order birefringent polymer retarders, which are not affected by the interference fringes typical of the crystalline super-achromatic wave plates (Samoylov et al 2004). More information on the optical design of HARPSpol can be found in the paper by Snik et al (2008 Notes.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712

Rusomarov

Kochukhov

Piskunov

et al. 2013

A&A

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Context. High-resolution spectropolarimetric observations provide simultaneous information about stellar magnetic field topologies and three-dimensional distributions of chemical elements. High-quality spectra in the Stokes IQUV parameters are currently available for very few early-type magnetic chemically peculiar stars. Here we present analysis of a unique full Stokes vector spectropolarimetric data set, acquired for the cool magnetic Ap star HD 24712 with a recently commissioned spectropolarimeter. Aims. The goal of our work is to examine the circular and linear polarization signatures inside spectral lines and to study variation of the stellar spectrum and magnetic observables as a function of rotational phase. Methods. HD 24712 was observed with the HARPSpol instrument at the 3.6-m ESO telescope over a period of 2010-2011. We achieved full rotational phase coverage with 43 individual Stokes parameter observations. The resulting spectra have a signal-to-noise ratio of 300-600 and resolving power exceeding 10 5 . The multiline technique of least-squares deconvolution (LSD) was applied to combine information from the spectral lines of Fe-peak and rare earth elements. Results. We used the HARPSPol spectra of HD 24712 to study the morphology of the Stokes profile shapes in individual spectral lines and in LSD Stokes profiles corresponding to different line masks. From the LSD Stokes V profiles we measured the longitudinal component of the magnetic field, B z , with an accuracy of 5-10 G. We also determined the net linear polarization from the LSD Stokes Q and U profiles. Combining previous B z measurements with our data allowed us to determine an improved rotational period of the star, P rot = 12.45812 ± 0.00019 d. We also measured the longitudinal magnetic field from the cores of Hα and Hβ lines. The analysis of B z measurements showed no evidence for a significant radial magnetic field gradient in the atmosphere of HD 24712. We used our B z and net linear polarization measurements to determine parameters of the dipolar magnetic field topology. We found that magnetic observables can be reasonably well reproduced by the dipolar model, although significant discrepancies remain at certain rotational phases. We discovered rotational modulation of the Hα core and related it to a non-uniform surface distribution of rare earth elements.

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“…It includes a GlanThompson polarizing prism, red and blue calibration quarter-wave retarders (QWR), and the science QWR. Super-achromatic QWR are based on the Pancharatnam design and consist of five stretched acrylic PMMA zeroorder retarder layers with their optical axes oriented at the specific angles (Samoylov et al 2004). No optical fringes at the level down to 0.025 % (1/4000) were detected on this type of retarder.…”

Section: Optical Designmentioning

confidence: 99%