Spectral flux distributions and total linear polarization spectrum of the GRB 171205A afterglow. (a) Spectral flux distribution at 4.1 days (blue circles and model dashed line) and 5.2 days (red squared points and model dashed line) after burst. The gray dotted lines indicate the simple power-law functions with indexes of 1.457 and −0.430. (b) Total linear polarization spectrum with the ALMA measurement 5.2 days after the burst. Dashed lines indicate the Faraday depolarized spectrum by assuming P₀ of 1% (green) and 0.5% (magenta). The dotted lines indicate the polarization spectrum without the Faraday depolarization effect (i.e., all electrons are energized by the relativistic shock) by assuming P₀ of 1% (green), 0.5% (magenta), and 0.33% (gray).