Top panel: histogram for the rise times for 32 of our SNe IIn. Our SNe IIn are divided into fast (magenta lines) and slow (blue lines) risers, with rise times 20 ± 6 d and 50 ± 11 d, respectively (as identified with GMM). Dashed lines show 1σ of the Gaussians. For reasons discussed in Sect. 5.3, we excluded PTF11qnf from the GMM analysis. Central panel: rise times of the two clusters of SNe IIn (slow and fast risers) compared to two well-known slow and fast risers from the literature (SN 2006gy, Smith et al. 2007; SN 1998S, Liu et al. 2000), with the rise-time ranges from the top panel overplotted. Bottom panel: light-curves of all the N(SNe) = 33 SNe in our sample with well-determined peak times matched at peak brightness (here, we include PTF11qnf for completeness).