T_eff – log g diagram for our 765 δ Scuti stars observed by TESS. The blue dots represent the positions of δ Scuti stars using parameters from the TIC, while the red dots correspond to a subgroup of δ Scuti stars with spectroscopic T_eff and log g values. The solid blue and red lines indicate the theoretical blue and red edges of the classical instability strip, respectively, for p modes with radial order n = 1, while the dashed blue and red lines represent radial order n = 6 according to Dupret et al. (2005).