T_eff−log g diagram showing our low-mass He-core pre-WD evolutionary tracks (thin dotted black lines) computed neglecting element diffusion. Numbers correspond to the stellar mass of each sequence. Green circles with error bars correspond to the known pre-ELMV stars (Maxted et al. 2013, 2014; Corti et al. 2016; Gianninas et al. 2016; Zhang et al. 2016), and small black circles depict the location of pre-ELM (nonvariable) WDs observed in the Kepler mission field (Rappaport et al. 2015; van Kerkwijk et al. 2010; Carter et al. 2011; Breton et al. 2012). The dashed blue line indicates the nonradial dipole (ℓ = 1) blue edge of the pre-ELMV instability domain due to the κ−γ mechanism acting at the He⁺ −He⁺⁺ partial ionization region, as obtained in Córsico et al. (2016a). The gray squares and triangles on the evolutionary tracks indicate the location of the template models analyzed in the text.