SK 143 : an SMC star with a galactic-type ultraviolet interstellar extinction.

Abstract

The ultraviolet extinction curve (1200-3000 A) deduced from IUE observations of the Small Magellanic Cloud star Sk 143 is presented. This curve is rather similar to the galactic one, with a large bump at 2200 A and a smaller rise shortward of 2000 A compared to the SMC extinction curve of Rocca-Volmerange et al. (1981). The N(H)/E(B-V) ratio estimated in two different ways has a value of 6 x 10 to the 21st per sq cm mag, quite comparable to the average galactic ratio, and ten times smaller than a preliminary SMC gas-to-dust ratio. Tentative explanations of the observed properties are given, including a possible binarity of Sk 143, the presence of a large amount of molecular hydrogen on the line of sight, and the existence of dust having the same properties as galactic dust.