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Proceedings Paper

The ZIMPOL high contrast imaging polarimeter for SPHERE: polarimetric high contrast commissioning results
Author(s): Ronald Roelfsema; Andreas Bazzon; Hans Martin Schmid; Johan Pragt; Alain Govaert; Daniel Gisler; Carsten Dominik; Andrea Baruffolo; Jean-Luc Beuzit; Anne Costille; Kjetil Dohlen; Mark Downing; Eddy Elswijk; Menno de Haan; Norbert Hubin; Markus Kasper; Christoph Keller; Jean-Louis Lizon; David Mouillet; Alexey Pavlov; Pascal Puget; Bernardo Salasnich; Jean-Francois Sauvage; Francois Wildi
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Paper Abstract

SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a second generation VLT instrument aimed at the direct detection of exo-planets. It has received its first light in May 2014. ZIMPOL (Zurich Imaging Polarimeter) is the imaging polarimeter subsystem of the SPHERE instrument. It's capable of both high accuracy and high sensitivity polarimetry but can also be used as a classical imager. It is located behind an extreme AO system and a stellar coronagraph. ZIMPOL operates at visible wavelengths which is best suited to detect the very faint reflected and hence polarized visible light from extra solar planets. During the SPHERE fourth commissioning period (October 2014) we have made deep coronagraphic observations of the bright star alpha Gru (mR = 1.75) to assess the high contrast polarimetric performance of SPHERE-ZIMPOL. We have integrated on the target for a total time of about 45 minutes during the meridian transit in the Very Broad Band filter (600 - 900 nm) with a classical Lyot coronagraph with 3 λ/D radius focal mask. We reduce the data by a combination of Polarized Background subtraction, Polarimetric Differential Imaging (PDI) and Angular Differential Imaging (ADI). We reach contrasts of 10-6 and 10-7 at a radial distances of respectively 7 and 14 lambda/D from the PSF core. At these radial distances we are respectively a factor of 10 and 2 above the photon noise limit. We discuss our results by considering the temporal and spatial speckle behavior close to the PSF core in combination with low order polarimetric aberrations.

Paper Details

Date Published: 26 July 2016
PDF: 18 pages
Proc. SPIE 9909, Adaptive Optics Systems V, 990927 (26 July 2016); doi: 10.1117/12.2231883
Show Author Affiliations
Ronald Roelfsema, NOVA ASTRON (Netherlands)
Andreas Bazzon, ETH Zurich (Switzerland)
Hans Martin Schmid, ETH Zurich (Switzerland)
Johan Pragt, NOVA ASTRON (Netherlands)
Alain Govaert, NOVA ASTRON (Netherlands)
Daniel Gisler, ETH Zurich (Switzerland)
Carsten Dominik, Univ. of Amsterdam (Netherlands)
Andrea Baruffolo, INAF - Osservatorio Astronomico di Padova (Italy)
Jean-Luc Beuzit, IPAG, Univ. Joseph Fourier (France)
Anne Costille, LAM, CNRS, Univ. de Provence (France)
Kjetil Dohlen, LAM, CNRS, Univ. de Provence (France)
Mark Downing, European Southern Observatory (Germany)
Eddy Elswijk, NOVA ASTRON (Netherlands)
Menno de Haan, NOVA ASTRON (Netherlands)
Norbert Hubin, European Southern Observatory (Germany)
Markus Kasper, European Southern Observatory (Germany)
Christoph Keller, Leiden Observatory (Netherlands)
Jean-Louis Lizon, European Southern Observatory (Germany)
David Mouillet, IPAG, Univ. Joseph Fourier (France)
Alexey Pavlov, Max-Planck-Institut fur Astronomie (Germany)
Pascal Puget, IPAG, Univ. Joseph Fourier (France)
Bernardo Salasnich, INAF - Osservatorio Astronomico di Padova (Italy)
Jean-Francois Sauvage, ONERA (France)
Francois Wildi, Univ. de Genève (Switzerland)

Published in SPIE Proceedings Vol. 9909:
Adaptive Optics Systems V
Enrico Marchetti; Laird M. Close; Jean-Pierre Véran, Editor(s)

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