2005MNRAS.357.1197W

The polarization behaviour of optical afterglows from two-component gamma-ray burst jets are investigated, assuming various configurations for the two components. In most cases, the observed polarization is dominated by the inner narrow component for a long period. Interestingly, it is revealed that different assumptions concerning the lateral expansion of the jet can lead to different evolutions of the position angle of polarization. The observed afterglow light curve and polarization behaviour of GRB 020813 can be well explained by the two-component jet model. In particular, the model is able to explain the constancy of the observed position angle in this event, given that the line of sight is slightly outside the narrow component.