* Astronomy

Discovery of Circularly Polarised Light in a GRB Afterglow

A large international team led by Klaas Wiersema from the University of Leicester has discovered circularly polarised optical emission in the afterglow of GRB 121024A. The study, published in Nature, used data mainly from FORS2 on the VLT, but also ACAM on the WHT. The ACAM data allowed the team to correctly identify a break in the light curve that confirmed the long standing prediction that an abrupt change of 90 degrees in the GRB linear polarisation happens when the Lorentz factor of the outwards jet decreases below a critical value.
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