Anomalous infrared emitters among A-type stars.

Spectroscopic observations of a sample of 26 stars have been analyzed in the blue and near-IR to find out if anomalous IR emitters (AIEs) have a spectral signature. It is found that many, but not all, such stars exhibit shell characteristics. Analysis of available IRAS photometric observations of A-type stars shows that the detection of circumstellar features depends strongly on the number of IR bands at which the object was observed. Out of the 707 stars observed by IRAS, 41 AIEs, or 5.7 percent, are found. Among nonsupergiant AIEs, 23 percent show shell features. The true percentage of AIEs among A-type stars is estimated to be 1.5 percent in a volume-corrected sample. A list of 24 stars which were apparently not previously detected as AIEs is given.