Temperature and radius of the thermal component in the prompt emission (gray points) and in the afterglow (blue points), plotted in the observer’s frame. Upper: single power-law fitting of the temperature in the prompt emission (dashed line, power-law index ~−0.5) clearly shows its extrapolation lays much higher than the temperature in the afterglow (power-law index ~−2). Bottom: radius in the afterglow (~10¹² cm) is much larger than the radius in the prompt emission (10⁹–10¹⁰ cm). The value of temperature and radius in the prompt emission are reproduced from (Izzo et al. 2012).