654 GHz CONTINUUM AND CO(6–5) OBSERVATIONS OF G240.31 0.07 WITH THE SUBMILLIMETER ARRAY

We report a dual-band observation at 223 and 654 GHz (460 mm) toward an ultracompact (UC) H ii region, G240.31 0.07, using the Submillimeter Array. With a beam size of 1.5 # 0.8 , the dust continuum emission is resolved into two clumps, with clump A well coincident with an H2O maser and the UC H ii region. The newly discovered clump, B, about 1.3 ( 8.3 # 10 AU) to the southwest of clump A, is also associated with masers and may be a more recent star-forming site. The continuum flux densities imply an opacity spectral H O 2 index of , suggestive of a value lower than the canonical 2.0 found in the interstellar medium and b p 1.5 0.3 in cold, massive cores. The presence of hot ( 100 K) molecular gas is derived by the brightness ratio of two lines in the 223 GHz band. A radial velocity difference of is found between the two 1 H CO 2.5 0.4 km s 2 clumps in CO(6–5) emission. The total (nebular and stellar) mass of roughly in the central region is 58 M, close to, but not much larger than, the minimum mass required for the two clumps to be gravitationally bound for binary rotation. Our continuum data do not suggest a large amount of matter associated with the knots H2 that were previously proposed to arise from a massive disk or envelope. Subject headings: circumstellar matter — stars: early-type — stars: individual (G240.31 0.07) — stars: pre–main-sequence — submillimeter — techniques: interferometric