2006A&A...458..533J

We present the results of a near-infrared monitoring programme of a selected sample of stars, initially suspected to be Mira variables and OH/IR stars, covering more than a decade of observations. The objects monitored cover the typical range of IRAS colours shown by O-rich stars on the asymptotic giant branch and show a surprisingly large diversity of variability properties. Sixteen objects are confirmed as large-amplitude variables. Periods between 360 and 1800^d and typical amplitudes 1^m≲ΔK≲2^m could be determined for nine of them. In three light curves, we find a systematic decrease in the mean brightness, and two light curves show pronounced asymmetry. One source, IRAS07222-2005, shows infrared colours typical of Mira variables, but it pulsates with a much longer period (≃1200^d) than a normal Mira. Two objects are either close to (IRAS03293+6010) or probably in (IRAS18299-1705) the post-AGB phase. In IRAS16029-3041 we found a systematic increase in the H-K colour of ≃1^m, which we interpret as evidence of a recent episode of enhanced mass loss. IRAS18576+0341, a heavily obscured luminous blue variable was also monitored. The star showed a continued decrease in brightness over a period of 7 years (1995-2002).