G_RVS bandwidth (delimited by the two vertical orange lines) extending over 24 nm from 846 to 870 nm. The fluxes of the available RVS epoch spectra of a source are integrated between these two wavelengths to estimate the magnitude grvs_mag, following the procedure outlined in Sects. 3 and 4. The Ca II triplet (at 850.035, 854.444, and 866.452 nm; rest-wavelengths in vacuum), prominent in the spectra of medium-temperature, FGK-, and late M-type stars, is the dominant feature found in the majority of RVS stellar spectra. The epoch CCD spectrum shown is that of a solar-type star with grvs_mag = 4.680 ± 0.045 mag.