Fitting and corner plot from wdtools. The left panel shows the fitting result of the hydrogen Balmer lines (Hα, Hβ, Hγ, Hδ, and Hϵ, from bottom to top) for the single-exposure spectrum of WDJ084253.03+230025.47 at MJD = 59230.347393, yielding T_eff and log g. The right panel is the corresponding corner plot, which illustrates the correlations between parameters and their marginal distributions, providing a visual representation of parameter uncertainties.