Colour-magnitude diagram showing HIP 99770 b, indicated by the black diamond, in relation to a literature population of low-mass stars, brown dwarfs, and exoplanets (see Appendix C of Bonnefoy et al. 2018 and references therein). All ExoGRAVITY targets (ESO ID 1104.C-0651; Lacour et al. 2020) and the companions so far detected via the Gaia-GRAVITY synergy (Winterhalder et al. 2024) are shown in light blue and ochre, respectively. Additionally, isochrones computed using the AMES-Dusty (Chabrier et al. 2000; Allard et al. 2001), AMES-Cond (Allard et al. 2001; Baraffe et al. 2003), and ATMO (Phillips et al. 2020) evolutionary models are shown for two ages: 1 Gyr (solid lines), and 100 Myr (dotted lines). The filters we used to extract these magnitudes and colours from the spectra are Paranal/SPHERE.IRDIS_B_Ks, IRDIS_D_K12_1, and IRDIS_D_K12_2.