Left: spectral energy distributions (SEDs) of LSQ13abf based on Bgri photometry. The SEDs have been shifted by the addition of an arbitrary constant for clarity and phases relative to the explosion epoch are reported. The symbols for the filters are as in Fig. 3. Each SED is fit with a BB function (red solid line) providing estimates of (right, top) the total luminosity (L_BB), (right, middle) the BB temperature (T_BB), and (right, bottom) the BB radius (R_BB). The early cooling phase is clearly visible with a prompt drop in the T_BB. Right: top panel, L_BB is fit with an Arnett model (solid red line), beginning from the fourth epoch post discovery when the process(es) producing the early peak is negligible. To perform the Arnett model fit, a peak velocity derived from the R_BB at the time of L_max (red dashed line in the bottom panel) was adopted. This BB velocity at peak was then reduced by ≈18%, which is the difference between the R_BB and the photospheric radius (green dots) derived at later epochs from the Fe II velocity. The first two measurements of L_BB, T_BB, and R_BB were also simultaneously fit with the post-shock breakout cooling model of Chevalier & Fransson (2008, blue line). The corresponding explosion parameters derived from the combined model are reported in the top-panel. Shown in magenta for comparison are the bolometric properties of a hydrodynamical model from Taddia et al. (2018b).