Introduction

A star showing the B[e] phenomenon appears in the group of unclassified B[e] stars, if its evolutionary phase is unknown. Reasons for failures in classifying stars are often the missing information on reliable stellar parameters and on the distances towards the stars. Especially the distance issue renders it notorically difficult to determine proper stellar luminosities, and this is why, for example, there exists a sub-sample of the unclassified B[e] stars which we call B[e] supergiant candidates, because these stars show indications of both a young, pre-main sequence (Herbig) nature as well as an evolved, B[e] supergiant nature, but their unclear luminosities makes a proper assignment to the group of B[e] supergiants at least very difficult. Some recent results on individual stars in this category can be found here.

Our aim in studying the unclassified B[e] stars is to find their most probable evolutionary stage. We are aware of the fact that some stars might be in binaries and that effects like binary interaction could be the reason for the B[e] phenomenon, or that especially close binaries might have merged, thereby leaving us with a remnant that can not be described by the stellar evolution theory of single stars. Nevertheless, detailed studies on each individual object are certainly necessary before we can draw any reliable conclusion about the current status and past evolution of these stars. We therefore devoted substantial time and effort to our studies of a few individual objects. Brief summaries of our results can be found below.