A SUBMILLIMETER RECOMBINATION LINE MASER IN MWC-349

We present the first detection of a recombination line maser at submil limeter wavelengths in MWC 349. The brightness temperature of the H26a lpha line at 353 GHz is larger than that of the lower frequency transi tions. Over the past 3 years, the H26alpha maser is less variable and probably more saturated than at lower frequencies. The velocity separa tion of the blue and red maser spikes is smaller than extrapolated fro m lower frequencies on the basis of circular rotation around a 32 M. c entral star. The sharp cutoff of the maser below 100 GHz is probably d ue to the free-free opacity of the strong stellar wind blocking the di sk containing the masers. The systematic differences between the blue and red maser spikes' velocities, line widths, intensities and trend o f saturation can be explained if the masers are on the ionized surface of a rotating disk with an additional small velocity component direct ed toward the center of rotation.