Narrow component of Hα plotted in velocity space. The spectral phases in days since discovery are reported on the right. The zero velocity was chosen to correspond to 6562.8 Å in the rest frame. We plotted (in red) the best fit to the line profile, which was achieved by fitting two Gaussian components, one for the absorption and one for the emission. The emission dominates at early epochs, while absorption becomes stronger at later epochs. We marked the BVZI with a dashed segmented line that ranges from −120 to −240 km s⁻¹.