HD 133656: a new high-latitude supergiant.

Abstract

In the course of our study of post-Asymptotic Giant Branch objects, we discovered that the seventh magnitude A supergiant HD 133656 has an infrared excess emission due to cool circumstellar dust, and that its photospheric abundance pattern is population II like. We present a detailed abundance study of the object, and discuss its nature in terms of post-AGB evolution: its galactic latitude, cold IR-excess, luminosity, abundances and photometric behaviour indicate HD 133656 to be a descendant of the F-type high-latitude supergiants. The deficiencies of the s-process elements are more difficult to understand in a post-AGB evolutinary scenario.