2025A&A...701A..78C

We used multiple epochs of high-contrast imaging spectrophotometric observations to determine the atmospheric characteristics and thermal evolution of two previously detected benchmark L dwarf companions, HD 112863 B and HD 206505 B. We analyzed IRDIS and IFS data from VLT/SPHERE of each companion, both of which have dynamical masses near the stellar-substellar boundary. We compared each companion with empirical spectral standards, and constrained their physical properties through atmospheric model fits. From these analyses, we estimate that HD 112863 B is spectral type L3 ± 1 and that HD 206505 B is spectral type L2 ± 1. Using the BT-Settl atmospheric model grids, we found a bimodal solution for the atmospheric model fit of HD 112863 B where T_eff = 1757_–36⁺³⁷ K or 2002_–24⁺²³ K and log g = 4.973_–0.063^+0.057 or 5.253_–0.033^+0.037, while for HD 206505 B, T_eff = 1754_–13⁺¹³ K and log g = 4.919_–0.029^+0.031. The results of a comparison of the bolometric luminosities of the companions with evolutionary models imply that both companions are likely above the hydrogen burning limit.