Near-infrared excesses of barium stars.

A sample of thirty one barium stars are found to exhibit weak (<0^m.1) infrared excesses at 1.6 μm and 4.8 μm. There is a possible correlation of the excess at 1.6 μm with the barium intensity (defined by the abnormal strength of the Ba II line at λ4554). Two mechanisms for the production of these excesses are discussed: (1) redistribution of energy from the Bond-Neff depression into the infrared, and (2) thermal emission caused by mass transfer in a binary system. The current observations do not allow one to conclusively differentiate between the two models, but the correlation of infrared excess at 1.6 μm with suppressed optical flux is suggestive of energy redistribution.