1998A&A...340..117L

We review the classification criteria for the B[e]-type stars (B type stars with forbidden emission lines in their optical spectrum) and we express these in terms of physical characteristics of the stars and the circumstellar (CS) matter. We show on the basis of observations that these criteria can be met in different kinds of stars of different mass and different evolutionary stages. We propose that the name "B[e] phenomenon" is more appropriate than the name "B[e] stars". We propose the definition of five classes of stars which show the B[e] phenomenon: (a) B[e] supergiants or "sgB[e] stars" (b) pre-main sequence B[e]-type stars or "HAeB[e] stars" (c) compact planetary nebulae B[e]-type stars or "cPNB[e] stars" (d) symbiotic B[e]-type stars or "SymB[e] stars" (e) unclassified B[e]-type stars or "unclB[e] stars" The primary and secondary classification criteria for each of these groups are defined. We also present lists of objects for each group, except for the SymB[e] stars. It is possible that some stars satisfy the criteria for more than one of the classes sgB[e], HAeB[e], cPNB[e] and SymB[e]. In that case the evolutionary phase of the star is unclear and the star should be assigned to class unclB[e].