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We investigated the ALMA science verification data of Orion KL and found aspectral signature of the vibrationally excited H2O maser line at 232.68670 GHz(nu2=1, 5,5,0-6,4,3). This line has been detected in circumstellar envelopes oflate-type stars so far but not in young stellar objects including Orion KL.Thus, this is the first detection of the 232 GHz vibrationally excited H2Omaser in star-forming regions. The distribution of the 232 GHz maser isconcentrated at the position of the radio Source I, which is remarkablydifferent from other molecular lines. The spectrum shows a double-peakstructure at the peak velocities of -2.1 and 13.3 km s-1. It appears to beconsistent with the 22 GHz H2O masers and 43 GHz SiO masers observed aroundSource I. Thus, the 232 GHz H2O maser around Source I would be excited by theinternal heating by an embedded protostar, being associated with either theroot of the outflows/jets or the circumstellar disk around Source I, as tracedby the 22 GHz H2O masers or 43 GHz SiO masers, respectively.

The first detection of the 232 GHz vibrationally excited H2O maser in Orion KL with ALMA