Branch et al. (2006) and Wang et al. (2009) diagrams. The left panel is populated with measurements from the CfA sample by Blondin et al. (2012) (open symbols) and from the CSP-I sample by Folatelli et al. (2013) (filled symbols). Right panel: only the measurements from Folatelli et al. (2013) are included. In both panels we added our own measurements of SN 2016hnk and the sample of subluminous 1991bg-like SNe Ia. SN 2002es was added only in the left panel because with a velocity of ∼5800 km s⁻¹ it falls outside the range shown in the right panel.