Exploration of the impact of A_v on the derived posterior values of T_eff and log (ɡ) for the ATMO grid of models. The A_v value is indicated by the color of each symbol. In the top panel, we compare T_eff and log (ɡ) from model runs v01 (A_v = 0) and v04 (A_v freely explored). Dashed lines connect the estimated values for a single target across the two runs. This shows that both T_eff and log (ɡ) are highly degenerate with A_v. In the lower panel, we perform a similar comparison between model runs v03 (A_v = 0) and v07 ($A_{\text{v}}=A_{\text{v}}^{Gaia}$). Here, the derived parameters exhibit improved physical consistency, underscoring the importance of utilizing fixed interstellar extinction values based on Gaia DR3 data (Lallement et al. 2022).