Spectrophotometric results from the Copernicus satellite. VI. Extinction by grains at wavelengths between 1200 and 1000 A

Extinction curves for the interstellar material are extended from 9 to 10 - 1 (1 A) for the reddened stars Oph, Per, Per, and a Cam. Good agreement with earlier results is obtained from 7.5 to 9 -i. in all cases, the extinction continues to increase in the far-ultraviolet. For Oph and Per, the increase of one in inverse micron units corresponds to an increase in extinction of about 3 mag, for an E (B - V) of one. The qualitative result is that smaller particles must be added to the general mix assumed for the interstellar material for all four stars. The feature expected for graphite at 1030 A does not stand out above the generally rising extinction, except possibly in a Cam. Subject headings:interstellar reddening - ultraviolet