Instability domain (grey shaded area) of low-order g modes excited by the ε mechanism on the log(g) vs. T_eff for each sequence of low-mass WD analyzed in this work. Stellar sequences are in units of solar mass. Red asterisks represent ELM (and pre-ELM) stars (Brown et al. 2010, 2013, 2016, 2020; Vennes et al. 2011; Gianninas et al. 2015; Kawka et al. 2015; Pelisoli & Vos 2019). Light-blue squares with dots represent pulsating low-mass WDs (ELMVs) (Hermes et al. 2012, 2013a,b; Kilic et al. 2015, 2018; Bell et al. 2017, 2018; Pelisoli et al. 2018), while black circles with dots correspond to pulsating low-mass pre-WDs (pre-ELMVs) (Maxted et al. 2013, 2014; Gianninas et al. 2016; Wang et al. 2020). Green circles correspond to sdBVs (Green et al. 2011), orange triangles represent BLAPs (Pietrukowicz et al. 2017), and pink triangles correspond to HG (High Gravity)-BLAPs (Kupfer et al. 2019). The evolutionary track of the He-core WD sequence with 0.1762 M_⊙ is included as a reference.