Infrared absorption at 9.7 m as an OH/IR star predictor

Forty-three infrared emitters whose IRAS LRS spectra show welldefined 9.7 μm absorption were searched for OH maser emission. Twenty-nine were identified as OH/IR stars, of which 18 were new detections. JHKL-band photometry was carried out on half the searched objects. The detected OH/IR stars are drawn in equal numbers from two different stellar populations. These two groups are distinguished observationally by the different expansion velocities of the OH shells. Two infrared sources are identified as probable young stellar objects from their OH main-line masers and two are possible proto-planetary nebulae.