Far-Ultraviolet Extinction in σ Scorpii
It was found earlier from OAO-2 data (Bless and Savage, 1972) that considerable variability with direction in space is present in both the shape and level (relative to B-V color excess) of the interstellar extinction curve in the far ultraviolet. The star σ Sco was shown to be a case of extremely low UV extinction, but there was some question of whether this could be due to scattered nebular light entering the large entrance slit of the Wisconsin spectrometer aboard OAO-2. We have obtained UV data on σ Sco using Copernicus (OAO-3), which has an entrance slit on the order of 103 times smaller in projected area than that of OAO-2, so that the contribution to the signal from scattered nebular light would be correspondingly smaller. We find very good agreement with the extinction curve of Bless and Savage, confirming the low UV extinction in the line of sight to σ Sco. The curve is extended down to 1000 Å, showing a continued rise towards short wavelengths.
KeywordsEntrance Slit Comparison Star Color Excess Extinction Curve Reddened Star
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