Volume 520, September-October 2010
|Number of page(s)||5|
|Published online||29 September 2010|
Letter to the Editor
Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, B5c, 4000 Liège, Belgium e-mail: email@example.com
2 Department of Physics, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA
3 Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
4 Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, 57 avenue d'Azereix, 65000 Tarbes, France
5 Institut Belge d'Aéronomie Spatiale, Avenue Circulaire 3, 1180 Bruxelles, Belgium
Accepted: 19 September 2010
We present new optical circular polarization measurements with typical uncertainties <0.1% for a sample of 21 quasars. All but two objects have null circular polarization. We use this result to constrain the polarization due to photon-pseudoscalar mixing along the line of sight. We detect significant (> 3σ) circular polarization in two blazars with high linear polarization and discuss the implications of this result for quasar physics. In particular, the recorded polarization degrees may be indicative of magnetic fields as strong as 1 kG or a significant contribution of inverse Compton scattering to the optical continuum.
Key words: quasars: general / polarization
Based on observations made with ESO Telescopes at the La Silla Observatory (Chile). ESO program ID: 79.A-0625(B).
Appendices are only available in electronic form at http://www.aanda.org
© ESO, 2010
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