Polarization posterior distributions for the two time intervals studied for GRB 170207A are shown with the 1σ and 2σ credibility intervals as well as that corresponding to 99% credibility. On the left, the posteriors are for the first selected time interval ranging from T = 0.0 s to T = 10.0 s (corresponding to the first emission period), while on the right the posteriors are for the second time bin ranging from T = 15.0 s to T = 25.0 s (corresponding to the second emission period). The polarization angle shown here is in the POLAR coordinate system; a rotation in the positive direction of 176 degrees transforms this to the coordinate system as defined by the IAU.