Fluxes, FWHM velocities, and velocity offsets between the broad and narrow component for the Hα line of iPTF13z. The values were obtained by least-squares fits of a two-component Lorentzian profile to spectra calibrated to photometry, de-reddened using E(B − V)_MW = 0.063 mag, and continuum subtracted. In the left panel, the broad Lorentzian is shown in green, the narrow component in blue, and their sum in red. The epochs of the spectra are given in days. The emission seen at 7000 km s^-1 and 7700 km s^-1 comes from host galaxy [S ii]. We used the ratio between the flux of [S ii] and the narrow Hα in the last spectrum (958 days) to remove the host galaxy contamination in the narrow emission of Hα of all the other spectra. We also show the resolution of each spectrum in the centre-right panel. The vertical dashed blue lines show the epochs of the light curve bump peaks (labelled B₁₋₄, upper right panel). The 1σ error of the least-squares fits were used as a measure of the statistical errors. The systematic errors were estimated by the difference between the Gaussian and Lorentzian fits to the lines. The error bars in the plots show statistical and systematic errors added in quadrature.