ASCA OBSERVATIONS OF THE WOLF-RAYET BINARY HD-193793

ASCA observed the Wolf-Rayet binary HD 193793 (WC 7 + O4-5) in 1993 Ju ne, only 3 months after periastron passage when the WC star was nearly in front of the 0 star. The X-ray spectra axe heavily absorbed below almost-equal-to 2 keV by the Wolf-Rayet wind and show a prominent emis sion line from He-like iron at 6.7 keV. A variable abundance Raymond-S mith model gives a temperature of kT almost-equal-to 3 keV (35 million K) and an equivalent hydrogen column density N(H) almost-equal-to 3 x 10(22) cm-2. This column density is a factor of almost-equal-to 10 la rger than the interstellar value, confirming that the absorption is pr imarily circumstellar. We derive an upper limit on the carbon abundanc e in the WC 7 wind of almost-equal-to 30 solar, and find evidence for a strong overabundance of neon as predicted by evolutionary models. Th e X-ray luminosity and derived column density agree well with that exp ected from a colliding wind shock, although comparison with a 1987 Gin ga observation fails to reveal the expected change in hard flux (2-6 k eV) with binary separation.