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
"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