We report the detection of the 1665 and 1667 MHz main lines of OH ( hydroxyl ) and upper limits on the 1612 MHz satellite line of OH towards the carbon-rich AGB star , IRC+10216 .
We find a beam averaged fractional abundance x ( { OH } ) \sim 4 \times 10 ^ { -8 } .
This detection supports the identification by Melnick et al .
( 2001 ) of the 1 _ { 10 } -1 _ { 01 } transition of water vapor with a 556.936 GHz emission feature detected towards IRC+10216 , since OH is the expected photodissociation product of water vapor .
The shape of the OH lines , however , differs significantly from the shape expected based on the observations of Melnick et al .
( 2001 ) .
Possible explanations for the anomalous shapes of the 1665 and 1667 MHz lines are discussed .
The most likely explanations for the unexpected OH line shapes are either masing or an asymmetric distribution of OH molecules around IRC+10216 .