FS CMa Type Binaries with the B[e] Phenomenon: Towards Solving a Long-standing Puzzle

The B[e] phenomenon is defined as the simultaneous presence of low-excitation forbidden line emission and strong infrared excess in the spectra of early-type stars. It was discovered in our galaxy nearly 40 years ago and is associated with objects at different evolutionary stages, ranging from the pre-main-sequence to the planetary nebula stage. Nearly half of the originally identified group members remained unclassified until recently. Our studies of the unclassified objects resulted in constraining their properties and fundamental parameters, expansion of the group, discovering binary features in many of its members, and suggesting a new name for the group (FS CMa type objects). Nevertheless, the nature of the secondary components and the evolutionary stage of the systems are still unclear. We review the group properties, present the best studied members, and discuss current understanding of the objects nature.