THE FAR-ULTRAVIOLET DUST ALBEDO IN THE UPPER-SCORPIUS SUBGROUP OF THESCORPIUS-OB2 ASSOCIATION

During NRL's Far Ultraviolet Cameras experiment on STS-39, four images of the giant reflection nebula encompassing the Upper Scorpius subgro up of the Sco OB2 association were obtained in two ultraviolet bandpas ses with lambda(eff) = 1362 Angstrom and 1769 Angstrom. From these ima ges and IUE and TD-1 stellar spectra, the ratio of nebular to stellar flux was calculated. The ratio ranged from 0.577 to 0.921 at 1362 Angs trom and 0.681 to 0.916 at 1769 Angstrom with the spread in the ratio arising mainly from uncertainties in the sky background. In order to a nalyze these images, a model utilizing Monte Carlo techniques to descr ibe radiative transfer in a spherical nebula with asymmetrically distr ibuted stars was developed by elaborating on previous work by Witt (19 77). This model was used to determine the range of albedos reproducing the observed nebular-to-stellar flux ratios while allowing the scatte ring phase function asymmetry to vary between 0.0 and 0.8. The resulti ng albedos were 0.47-0.70 at 1362 Angstrom and 0.55-0.72 at 1769 Angst rom.