Pre-processed spectra of CME candidate 1 (four solid lines) and the reference spectra of the host star (two dashed lines). Each spectrum is marked with the LAMOST local modified Julian day (LMJD) at the time of exposure. Panel A is part of the blue arm (5150–5200 Å), which contains the Mg I triplet lines (5168.94 Å, 5174.13 Å, and 5185.10 Å) and the Fe II 5170.47 Å line. The rest wavelengths of these chromospheric lines are marked with the vertical dotted black lines. Panel B is part of the red arm (6450–6700 Å), which contains the Hα (6564.61 Å) line and the He I 6680 Å line. The vacuum wavelengths of these lines are taken from van Hoof (2018). In panels A and B, the spectra of CME candidate 1 observed at different times are shifted on the vertical axis for a better illustration. In order to clearly show the changes in the Hα line profiles, the spectra near the Hα line are plotted in panel C.