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A unique infrared spectropolarimetric unit for CRIRES+
Author(s): Nikolai Piskunov; Eric Stempels; Alexis Lavail; Michael Escuti; Frans Snik; Andrey Dolgopolov; Milan Rozel; Candice Durandet; Artie Hatzes; Paul Bristow; Anna Brucalassi; Claudio Cumani; Reinhold J. Dorn; Andreas Haimerl; Ulrike Heiter; Renate Hinterschuster; Roman Follert; Derek Ives; Yves Jung; Florian Kerber; Barbara Klein; Jean-Louis Lizon; Thomas Marquart; Ignacio Molina-Conde; Luca Pasquini; Jérôme Paufique; Ernesto Oliva; Ansgar Reiners; Ulf Seemann; Jörg Stegmeier; Sebastien Tordo; Elena Valenti
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Paper Abstract

High-resolution infrared spectropolarimetry has many science applications in astrophysics. One of them is measuring weak magnetic fields using the Zeeman effect. Infrared domain is particularly advantageous as Zeeman splitting of spectral lines is proportional to the square of the wavelength while the intrinsic width of the line cores increases only linearly. Important science cases include detection and monitoring of global magnetic fields on solar-type stars, study of the magnetic field evolution from stellar formation to the final stages of the stellar life with massive stellar winds, and the dynamo mechanism operation across the boundary between fully- and partially-convective stars. CRIRES+ (the CRIRES upgrade project) includes a novel spectropolarimetric unit (SPU) based on polar- ization gratings. The novel design allows to perform beam-splitting very early in the optical path, directly after the tertiary mirror of the telescope (the ESO Very Large Telescope, VLT), minimizing instrumental polariza- tion. The new SPU performs polarization beam-splitting in the near-infrared while keeping the telescope beam mostly unchanged in the optical domain, making it compatible with the adaptive optics system of the CRIRES+ instrument. The SPU consists of four beam-splitters optimized for measuring circular and linear polarization of spectral lines in YJ and HK bands. The SPU can perform beam switching allowing to correct for throughput in each beam and for variations in detector pixel sensitivity. Other new features of CRIRES+, such as substantially increased wavelength coverage, stability and advanced data reduction pipeline will further enhance the sensitivity of the polarimetric mode. The combination of the SPU, CRIRES+ and the VLT is a unique facility for making major progress in understanding stellar activity. In this article we present the design of the SPU, laboratory measurements of individual components and of the whole unit as well as the performance prediction for the operation at the VLT.

Paper Details

Date Published: 6 July 2018
PDF: 12 pages
Proc. SPIE 10702, Ground-based and Airborne Instrumentation for Astronomy VII, 1070234 (6 July 2018); doi: 10.1117/12.2313512
Show Author Affiliations
Nikolai Piskunov, Uppsala Univ. (Sweden)
Eric Stempels, Uppsala Univ. (Sweden)
Alexis Lavail, Uppsala Univ. (Sweden)
Michael Escuti, Geometric-Phase Photonics Lab., North Carolina State Univ. (United States)
Frans Snik, Leiden Observatory (Netherlands)
Andrey Dolgopolov, Crimean Astrophysical Observatory (Ukraine)
Milan Rozel, Uppsala Univ. (Sweden)
Candice Durandet, Uppsala Univ. (Sweden)
Artie Hatzes, Thüringer Landessternwarte Tautenburg (Germany)
Paul Bristow, European Southern Observatory (Germany)
Anna Brucalassi, European Southern Observatory (Germany)
Claudio Cumani, European Southern Observatory (Germany)
Reinhold J. Dorn, European Southern Observatory (Germany)
Andreas Haimerl, European Southern Observatory (Germany)
Ulrike Heiter, Uppsala Univ. (Sweden)
Renate Hinterschuster, European Southern Observatory (Germany)
Roman Follert, Thüringer Landessternwarte Tautenburg (Germany)
Derek Ives, European Southern Observatory (Germany)
Yves Jung, European Southern Observatory (Germany)
Florian Kerber, European Southern Observatory (Germany)
Barbara Klein, European Southern Observatory (Germany)
Jean-Louis Lizon, European Southern Observatory (Germany)
Thomas Marquart, Uppsala Univ. (Sweden)
Ignacio Molina-Conde, European Southern Observatory (Germany)
Luca Pasquini, European Southern Observatory (Germany)
Jérôme Paufique, European Southern Observatory (Germany)
Ernesto Oliva, INAF - Osservatorio Astrofisico di Arcetri (Italy)
Ansgar Reiners, Institut für Astrophysik, Georg-August Univ. Göttingen (Germany)
Ulf Seemann, Institut für Astrophysik, Georg-August-Univ. Göttingen (Germany)
Jörg Stegmeier, European Southern Observatory (Germany)
Sebastien Tordo, European Southern Observatory (Germany)
Elena Valenti, European Southern Observatory (Germany)


Published in SPIE Proceedings Vol. 10702:
Ground-based and Airborne Instrumentation for Astronomy VII
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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