Equivalent widths (EW) of the four potassium absorption lines detected at 1.169, 1.177, 1.244, and 1.253 μm. To confirm the young age of X-SHYNE’s objects, we compared their EWs (pink) with the EW calculated for the low, intermediate, and field gravity objects from the library of spectra published by Martin et al. (2017) (blue). To improve the clarity of the plot, objects that share the same spectral type have been evenly distributed within a range corresponding to their spectral type ±1.