Relationships between Brγ emission region sizes and selected stellar properties. Top: fitted HWHM of the Brγ pure line emission region of the central channel versus the mass-accretion rate. The latter is depicted in two forms: once as a grey bar which denotes the range of values found in the literature on the respective source, then as the instantaneous mass-accretion rate, which was derived from the equivalent width of the GRAVITY Brγ spectra. The colour coding represents the classification of the sample objects as either weak (green) or intermediate to strong accretors (red). Most of the T Tauri stars cluster in a 4–7 R_* range, which is of the order of typical magnetospheric sizes. Bottom: Brγ HWHM versus accretion luminosities. The colour coding corresponds to the upper plot.