IRAS DETECTIONS OF METAL-POOR RED GIANTS

A number of relatively bright metal-poor red giants from the I-ID and ED catalogs are found to have been detected by the IRAS satellite. Dat a for these stars have been retrieved from the IRAS Point Source Catal og (PSC) and/or the Faint Source Catalog (FSC). The majority of metal- poor giants in these samples fall along relatively well-defined sequen ces in plots of V - [12] versus B - V and V - I; for these stars, the 12 mu m flux detected is presumed to arise from the photosphere. Only a subset of stars detected at 12 pm were detected at 25 mu m; these ar e displayed in a plot of [12] - [25] versus V - [12]. There are a smal l number of giants that exhibit notable 12 and/or 25 mu m excesses rel ative to the mean sequences defined by the bulk of the sample. Those s tars with the most unambiguous evidence for infrared excesses are vari able stars, either long-period or semiregular variables or RV Tauri st ars. As such, those stars exhibiting infrared excesses in the metal-po or giant sample are likely in the asymptotic giant branch (AGB) or pos t-AGE phase of evolution. There is no clear evidence for nonvariable f irst-ascent red giants having been detected among the infrared-excess stars. In fact, some metal-poor red giants known to exhibit outflows i n their chromospheres do not show infrared excesses. A Population II s tar 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.