Doppler shift of excess flare emission of the line cores. The missing data points indicate that a Gaussian fit was impossible, which causes the gap at about 3 h, where the minimum activity spectrum is located. All of the activity indicators shift to the blue before the flare onset (noted by vertical dotted line). Green line represents the expected Doppler shift of such an object, at 43 deg latitude, if it were to emerge onto the blue limb of the disk 3.72 h into the observation run.