Left panel: distribution of the burst BB temperatures along with the best-fit lognormal function (solid line). The vertical dashed line is the highest BB temperature measured for the persistent emission. The arrow indicates the surface temperature evolution trend during the outburst decay. Middle panel: distribution of the burst BB area along with the best-fit lognormal function (solid line). The vertical dashed line is the BB area of the persistent emission. Right panel: burst BB temperature vs. flux, measured in the 0.5–10 keV energy band.