the occurrence of supergiants at high galactic latitudes has long been an enigma: how can massive stars reach such large distances from the galactic plane? the iras mission has detected ir excesses in many of these stars. a new interpretation is then that they are not genuine massive stars, but rather low-mass stars in an advanced stage of evolution, presumably post-agb. stars in this short phase of evolution had virtually not been found before iras. still, for some high-latitude supergiants, no ir excess has been found so far. phot observations will answer if this is just a matter of iras detection limit. failure of detecting ir excesses in these stars may reopen the question of massive star occurrence far from the galactic plane. the objects for which an ir excess is found, show a perplexing diversity in their appearances. mass loss histories appear to change from star to star, photospheric abundances often are not conform to expectation, peculiar emission features are observed in several stars. many turn out to be binaries: the suspicion arises that some of these stars actually are .blue agb stars., that underwent blueward evolution after mass transfer. sws aot01 observations will reveal in unprecedented detail the ir energy distribution and emission features of these stars. modelling the energy distribution enables to enravel the mass loss history. we focus on stars that are also bright in the optical and the uv: ir features can then be linked to photospheric abundances and possibly to circumstellar absorption features. this proposal is linked with the sws central program proposal by rens waters.
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, 1999, Circumstellar Matter Around High-Latitude Supergiants High-Latitude Supergiants, 1.0, European Space Agency, https://doi.org/10.5270/esa-slmrqq8
