The sources were observed with the MkIII infrared photometer (Glass
1985) on the SAAO 1.9-m telescope. A chopping secondary mirror
defines two effective apertures: on-source (star) and off-source
(background). Square apertures of 9'' or 12'' were used, depending on
the seeing. A single observation module consisted of a 40 s
integration, with the star placed alternately in the two apertures by
nodding the telescope. These individual 40 s observations were then
repeated, typically 2-4 times per filter, until a sufficient precision
(standard error 
0.01 magnitudes) was achieved. The observations
were obtained in the SAAO JHK system (1.25, 1.65 & 2.2 microns;
Carter 1990) in photometric conditions, transformations being
affected from regular observations of IR standards.
The observations were carried out during the period December 1993 - November 1995 at approximately quarterly intervals. The result from the observation of each source taken on a good photometric night, and a measure of its variability are presented in Table 1 (click here).
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