Distributions of the known members (identified in the SIMBAD database) shown in contours on the [J] − [K] versus [K] −  color–color diagram: a) C-rich AGBs (red; group E), AGBs (black) and OH/IR stars (blue) (O-rich AGBs; group F); b) T Tauri (brown) and YSOs (green) (group A); c) Be stars (including Wolf-Rayet stars; brown) and emission-line stars (green) (group B); d) normal stars including O–M giants and dwarfs (green; group C); e) S-stars (green; group D), and post-AGBs and planetary nebulae (brown; group G); and f) normal and starburst galaxies (green) and Seyferts (brown) (group H). The occupation zones for the groups A–H are summarized in g). The contours show 20%, 50%, and 80% of the peak value. The SIMBAD definitions of the members of the groups A–H are summarized in Table 1.
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