Top: normalized spectra of Hα line Å during transit event of planet c with their color indicating their observation number (epoch). The dashed line marks the line center at 6564.7 Å, and the dotted lines indicate 1 Å from the line center. Left: excess absorption of Hα variation by time, with the absorption referenced by an average postegress spectrum, and calculated in a bandpass of 2 Å centered at 6564.7 Å. The color scale is the same for the top subplot. The dashed line and dotted line indicate midtransit and egress, respectively. Notably, ingress is not included. Main (bottom right): the measured Hα line profile residuals as a function of time and wavelength. The dashed line and vertical dotted line correspond to the top subplot the top subplot, while the horizontal dotted line indicates the egress as in the left subplot. The predicted planetary velocity is marked by green solid line. An excess absorption and blueshift can be seen in dark blue.