Detection of methanol in a class 0 protostellar disk

We report the detection of emission from methanol in a compact source coinc ident with the position of the L1157 infrared source, which we attribute to molecules in the disk surrounding this young, class 0 protostellar object. Using the Caltech Owens Valley Millimeter Array with a synthesized beam si ze of 2 ", we detect spatially unresolved methanol emission in the 2(k)-1(k ) transitions at 3 mm wavelength, which is coincident in position with the peak of the continuum emission. The gas-phase methanol could be located in the central region (<100 AU radius) of a flat disk or in an extended heated surface layer (similar to 200 AU radius) of a flared disk. The fractional abundance of methanol X(CH3OH) is similar to 2 x 10(-8) in the flat disk mo del and similar to 3 x 10(-7) for the surface layer of a flared disk. The l arge variation in the fractional abundance between the warm portion of the flared disk and the disk as a whole makes it plausible that substantial che mical processing via depletion and desorption has occurred.