We report a dual-band observation at 223 and 654 GHz ( 460 µm ) toward an ultracompact ( UC ) H ii region , G240.31+0.07 , with the Submillimeter Array .
With a beam size of 1 \farcs 5 \times 0 \farcs 8 , the dust continuum emission is resolved into two clumps , with clump A coincident well with an \mathrm { H _ { 2 } O } maser and the UC H ii region .
The newly discovered clump , B , about 1 \farcs 3 ( \simeq 8.3 \times 10 ^ { 3 } \mathrm { AU } ) to the southwest of clump A , is also associated with \mathrm { H _ { 2 } O } masers and may be a more recent star-forming site .
The continuum flux densities imply an opacity spectral index of \beta = 1.5 \pm 0.3 , suggestive of a value lower than the canonical 2.0 found in the interstellar medium and in cold , massive cores .
The presence of hot ( \simeq 100 \mathrm { K } ) molecular gas is derived by the brightness ratio of two \mathrm { H _ { 2 } CO } lines in the 223 GHz band .
A radial velocity difference of 2.5 \pm 0.4 \mathrm { km s ^ { -1 } } is found between the two clumps in \mathrm { C ^ { 18 } O ( 6 - 5 ) } emission .
The total ( nebular and stellar ) mass of roughly 58 M _ { \sun } in the central region is close to , but not by far 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 \mathrm { H _ { 2 } } knots that were previously proposed to arise from a massive disk or envelope .