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GRB 030329 polarization variations

Significant polarization variability from 0.3 to 2.5 % on timescales down to hours throughout a 38-day period of a gamma ray burst optical afterglow has been observed. This particular behaviour has not been predicted by any of the major theories.

Nature 426, 157 (13. November 2003) publishes the article:

"The evolution of the polarization of the afterglow of GRB 030329"

Jochen Greiner, Sylvio Klose, Klaus Reinsch, Hans Martin Schmid, Re'em Sari, Dieter Hartmann, Chryssa Kouveliotou, Arne Rau, Eliana Palazzi, Christian Straubmeier, Bringfried Stecklum, Sergej Zharikov, Gaghik Tovmassian, Otto Bärnbantner, Christop Ries, Emmanuel Jehin, Arne Henden, Anlaug A. Kaas, Tommy Grav, Jens Hjorth, Holger Pedersen, Ralph A.M.J. Wijers, Andreas Kaufer, Hye-Sook Park, Grant Williams, Olaf Reimer

based on a set of polarimetric observations, of which one was obtained with ALFOSC/FAPOL at the NOT. For more information, please, check below:

The NOT and polarimetry of GRBs

The first ever polarization measurement of a GRB afterglow was obtained by the NOT in 1999 (Hjorth et al. 1999, Science 283, 2073). At the time it was thought that GRB afterglows might be polarized by of the order of about 10%. The observations however gave an upper limit of 2.3 % on the polarisation of GRB 990123. The first detection of polarization (at 1.7 %) was obtained at the VLT in May 1999.

The second NOT polarization observation of a GRB afterglow was obtained in 2001 and resulted in a marginal detection at 1.36 +- 0.64% (Bjornsson et al., 2002, ApJ 579, L59).

The third set of NOT observations were obtained in October 2002 of GRB 021004 and contributed to the first published polarization lightcurve containing more than a few data points (Rol et al. 2003, A&A 405, L23).

The fourth NOT observation is the one reported in the Nature paper above. Polarization of 2.5 +- 0.5 % 4.5 days after the GRB, i.e. highly significant. The reported polarization lightcurve contains more than 30 data points which represent almost an order of magnitude improvement.

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