The light curve of the semiregular variable L2 Puppis – I. A recent dimming event from dust

The nearby Mira-like variable L2 Pup is shown to be undergoing an unprecedented dimming episode. The stability of the period rules out intrinsi c changes to the star, leaving dust formation along the line of sight as the most likely explanation. Episodic dust obscuration events are fairly common in carbon stars but have not been seen in oxygen-rich stars. We also present a 10-� m spectrum, taken with the Japanese IRTS satellite, showing strong silicate emission which can be fitted with a detached, thin dust s hell, containing silicates and corundum.