OSIRIS/GTC low-resolution spectra of the ten σ Orionis stars and brown dwarfs. Names are labelled. The noisy region of the brown dwarf Mayrit 872139 and 1196092 spectra bluewards of 5000 Å are not plotted. In the bottom, vertical lines indicate key spectral signposts: the hydrogen Balmer series (very long [red] lines), calcium, sodium, magnesium, and lithium in absorption (long [black] lines), and helium and forbidden oxygen, nitrogen, and sulfur in emission (short [magenta] lines).