THE APPARENT SIZES OF THE 6(2)-6(1) E-TYPE METHANOL MASERS IN OMC-1

The 6(2)-6(1) E transition of CH3OH has been observed toward the Orion KL region with an angular resolution of 0.'' 07 and frequency resolut ion of 12 kHz (0.15 km s(-1)) at two epochs, 1 year apart. The observa tions have a sensitivity of 1 Jy beam(-1) (corresponding to a main bea m brightness temperature of 4 x 10(5) K). Only the brightest masers pr eviously measured with 3 '' resolution are detected; these are resolve d into several bright features. The brightness temperatures of the det ected masers range from 2 x 10(6) to 3 x 10(7) K, with apparent sizes in the range 22-56 AU. From the trends of radial velocity versus posit ion, the observed line widths of the masers may be explained as blends of individual narrower features, each with line widths less than the frequency resolution of these measurements. The intensities of the mas ers increase with decreasing apparent size. This is interpreted as evi dence that the excitation process plays a larger role than path length in determining maser intensity; our measurement of narrow line widths supports this interpretation. The CH3OH masers are probably collision ally pumped and formed in very turbulent regions. The kinetic temperat ures are approximate to 100 K, corresponding to sound speeds of order 2 km s(-1). From this, intensity variations are expected on timescales of years, or longer. At both epochs the majority of the maser feature s are located in the same relative positions with approximately the sa me flux densities. However, some of the masers appear to vary on times cales of a year. Variations in intensity of the strongest maser featur e may have been detected over a year's time. Further, two weak maser f eatures that appeared in 1990 were not detected in 1991.