The Object Type in Simbad is defined as a hierarchical classification, which emphasizes the physical nature of the object rather than a peculiar emission in some region of the electromagnetic spectrum or the location in peculiar clusters or external galaxies. The hierarchies between object types is made as, for instance, a RR Lyrae Star is in the hierarchy of Variable Stars, and also in the hierarchy of Horizontal Branch Stars.
Therefore objects are classified as peculiar emitters (Radio, IR, Red, Blue, UV, X or gamma) only if nothing more about the nature of the object is known, i.e. it cannot be decided whether the object is a star, a multiple system, a nebula or a galaxy.
Here is a list of labels (compared with previous version). Please send us an email if you have more questions cds-question@astro.unistra.fr.
Each class has normally a standard designation, a condensed one (used in tables) and an extended explanation. The "hierarchy" column gives the list of types used behind selection criteria queries/TAP/Aladin.