Oxygen-rich late-type star lightcurves in the 1-20microm. range.

A study of the variability properties of OH/IR sources in the infrared range is presented which is aimed at improving the list of well-studied OH/IR sources. A sample includes optically identified miras, M-type supergiants, type II OH/IR sources, and one unidentified object. It is concluded that all OH/IR sources in the sample are variable with periods in the range from 470 to about 2000 days, and with large amplitudes from 1.0 to 3.0 magnitude. Based on their variability properties OH/IR sources can be divided into two broad classes. The first class includes objects with periods in the range of 450-700 days, which are well-defined but have amplitudes varying from cycle to cycle. The second class includes objects with periods from 800 to 1600 days and, possibly, 2000 days.