Absolute calibration of the infrared flux from Vega at 1.24, 2.20,3.76 and 4.6  m by comparison with a standard furnace

A determination has been made at Tenerife of the absolute monochromatic flux from Vega at 1.24, 2.20, 3.76 and 4.6 μm with an accuracy of 3 per cent for λ< 4 μm and ∼ 12 per cent for λ > 4 μm, using a calibrated furnace as standard. The technique differs in detail from that used for similar observations in 1980. The results confirm in general those obtained in 1980, especially at λ ∼ 3.8 μm. Both the 1980 and the 1981 observations show an excess flux of about 7 per cent for λ > 2 μm compared to that calculated by Dreiling & Bell using their model atmosphere for Vega.