10-YEAR OBSERVATIONS OF THE H2O MASER IN S-140

The results of homogeneous systematic observations of 1,35 cm H2O mase r in S 140, performed in 1981-1992 with the 22-m radio telescope of th e Radio Astronomical Station of the Lebedev Physical Institute at Push chino, are presented. The maser emission is localized in three narrow, symmetrically spaced intervals of radial velocity, and this is interp reted as a result of maser amplification in a Keplerian (protoplanetar y?) disk surrounding a young star. The observed anti-correlation of th e intensities of the central and the side components, as well as a wea k and-correlation of the two side components are explained by the mase r mode competition in a partly saturated maser with a variable pumping rate. The radial velocities of the triplet components are subject to a complicated drift. Supposing that the drift is caused by the passage of dense gas clumps across the amplification region, we crudely estim ated the dimensions of the disk at the region of maser amplification ( <30 A. U.) and the mass of the central star (<M.). The consecutive (<< relay race>>) flaring up and dying down of the subsources representing the red component is explained by a chancy superposition on the line of sight of two clusters of gas condensations. These clusters could be proto-satellite systems of two giant protoplanets. If the hypothesis of the disk geometry for the H2O maser S 140 is correct, an important information about the dimensions of the disk and its inhomogeneities, as well as about the mass of the central star will be provided by VLBI . The measurement of the linear polarization of the triplet components , augmented with VLBI, could shed light on the structure and strength of the magnetic field within the disk.