Theoretical gravity-darkening exponents and observed values for TT Aur (open square) and V Pup (open triangle). The semi-empirical values of β₁ reported by Rafert & Twigg (1980) and Djurasevic et al. (2003, 2006) are represented by asterisks and full squares, respectively. The continuous line indicates the theoretical β₁ (Eq. (9)) for the case α = −0.1, the dashed line denotes α = −0.3, and the dotted line indicates the case α = −0.2 for the Kramer law. The dashed-dotted line represents the calculations adopting the triangle strategy method (Claret 2000).