Equivalent width of the Ca i λ422.7 nm line vs. spectral type. Red filled circles denote observations presented in this work, black empty circles are from template stars (Manara et al. 2013b). Due to strong emission lines inside the absorption feature, we determine a lower limit for J0843 (red arrow). The black line denotes the relation between the equivalent widths and spectral types of non-accreting stars (Eq. (1)).