Spectroscopic signature of the transiting planet in the Na I line. Top panel: residuals between spectra during the transit and out-of transit spectrum, with different colors indicating the time during transit. Lower panel: residuals shown as a dynamic spectrum with color indicating normalized residual flux, and a brighter color indicating larger values. The white dashed line shows the planetary path. The plot covers a velocity range of ±20 km s⁻¹ around the line center.