1998PASP..110.1119S

A number of relatively bright metal-poor red giants from the HD and BD catalogs are found to have been detected by the IRAS satellite. Data for these stars have been retrieved from the IRAS Point Source Catalog (PSC) and/or the Faint Source Catalog (FSC). The majority of metal-poor giants in these samples fall along relatively well-defined sequences in plots of V-[12] versus B-V and V-I; for these stars, the 12 µm flux detected is presumed to arise from the photosphere. Only a subset of stars detected at 12 µm were detected at 25 µm; these are displayed in a plot of [12]-[25] versus V-[12]. There are a small number of giants that exhibit notable 12 and/or 25 µm excesses relative to the mean sequences defined by the bulk of the sample. Those stars with the most unambiguous evidence for infrared excesses are variable stars, either long-period or semiregular variables or RV Tauri stars. As such, those stars exhibiting infrared excesses in the metal-poor giant sample are likely in the asymptotic giant branch (AGB) or post-AGB phase of evolution. There is no clear evidence for nonvariable first-ascent red giants having been detected among the infrared-excess stars. In fact, some metal-poor red giants known to exhibit outflows in their chromospheres do not show infrared excesses. A Population II star ascending the red giant branch for the first time appears to have too low a mass-loss rate to be recognizable as an infrared-excess star in the IRAS PSC or FSC.