An infrared study of galactic OH/IR stars

We present optical and near-infrared finding charts taken from the DSS and 2MASS surveys of 94 IRAS sources selected from the GLMP catalogue, and accurate astrometry (≈0.2´´) for most of them. Selection criteria were very red IRAS colours representative for OH/IR stars with optically thick circumstellar shells and the presence of variability according to the IRAS variability index ($\rm VAR>50$). The main photometric properties of the stars in this “GLMP sample” are presented, discussed and compared with the correspondent properties of the “Arecibo sample” of OH/IR stars studied nearlier. We find that 37% of the sample ($N=34$) has no counterpart in the 2MASS, implying extremely high optical depths of their shells. Most of the sources identified in the 2MASS are faint ($K\ga8$) and are of very red colour in the near-infrared, as expected. The brightest 2MASS counterpart ($K=5.3$ mag) was found for IRAS 18299–1705. Its blue colour $H-K=1.3$ suggests that IRAS 18299–1705 is a post-AGB star. Few GLMP sources have faint but relatively blue counterparts. They might be misidentifed field stars or stars that recently experienced a drop of their mass loss rates. The “GLMP sample” in general is made of oxygen-rich AGB stars, which are highly obscured by their circumstellar shells. They belong to the same population as the reddest OH/IR stars in the “Arecibo sample”.