IUE observations of lines of sight with peculiar ultraviolet extinction.

Low resolution IUE data were used to derive UV extinction curves for a group of stars known to have peculiar extinction parameters from ANS data. The resulting curves have a wide range of appearances. Although the ratio E(BUMP)/E(B-V) differs by a factor of three in the extreme cases, the wavelength of maximum absorption does not appear to change. No evidence for new fine structure in UV extinction was found. The structure near 62 micrometers in the existing mean extinction curves appears to be the result of luminosity mismatch errors. The new extinction curves have shapes that separate into two distinct classes; those associated with clear field extinction and those associated with extinction in dense nebular environments. The range of variation in the curves is so large, the common practice of ironing out the bump can produce enormous errors in the resultant UV energy distributions when E(B-V) 0.3.