The HARPS polarimeter

astro-ph.IM

/ Authors

Frans Snik, Oleg Kochukhov, Nikolai Piskunov, Michiel Rodenhuis, Sandra Jeffers, Christoph Keller, Andrey Dolgopolov, Eric Stempels, Vitaly Makaganiuk, Jeff Valenti

and 1 more author

Christopher Johns-Krull

/ Abstract

We recently commissioned the polarimetric upgrade of the HARPS spectrograph at ESO's 3.6-m telescope at La Silla, Chile. The HARPS polarimeter is capable of full Stokes spectropolarimetry with large sensitivity and accuracy, taking advantage of the large spectral resolution and stability of HARPS. In this paper we present the instrument design and its polarimetric performance. The first HARPSpol observations show that it can attain a polarimetric sensitivity of ~10^-5 (after addition of many lines) and that no significant instrumental polarization effects are present.