H band HI Brackett excitation diagram for the HBe of ZCMa (circles). All line fluxes are normalized to the HI Brackett 11 line. Open circles show the lines that are probably contaminated. Blue triangles show the line ratios detected in EX Lupi (Kóspál et al. 2011b). The green curves are predictions from case B recombination from Hummer & Storey (1987) for T = 10⁴ K and n = 10⁸ cm^-3 (lower curve) and for T = 500 K and n = 10⁷ cm^-3 (upper curve). The red dotted lines show expected line ratios from blackbody emission at T = 1000 K (lower curve) and T = 10⁴ K (upper curve).