The very slow wind from the pulsating semiregular red giant, L2 Puppis

We have obtained 11.7 and 17.9 mum images at the Keck I telescope of the circumstellar dust emission from L-2 Pup, which is one of the nearest (D = 61 pc) mass-losing, pulsating red giants that has a substantial infrared excess. We propose that the star is losing mass at a rate of similar to3 x 10(-7) M-. yr(-1). Given its relatively low luminosity (similar to1500 L-.), relatively high effective temperature (near 3400 K), relatively short period (similar to140 days), and inferred gas outflow speed of 3.5 km s(-1), standard models for dust-driven mass loss do not apply. Instead, the wind may be driven by the stellar pulsations, with radiation pressure on dust being relatively unimportant, as described in some recent calculations. L-2 Pup may serve as the prototype of this phase of stellar evolution, in which a star could lose similar to15% of its initial main-sequence mass.